May 12, 2021

The Coronavirus Pandemic – Answering Your Questions

Coronavirus virion

Students may have questions related to the coronavirus pandemic or you may be teaching about it. This page provides information about some of the questions that have been pressing during the course of the pandemic. If you would like to see other questions addressed, you can email questions to To see the archive of questions from 2020, please visit the Archived Coronavirus Pandemic Questions page. We also have a dedicated page on the VEC website. Go to for even more information.

May 12  

What is a vaccine mandate? 

See if you can identify which of these statements are true:

  • It is illegal to drive faster than the posted speed limit.  
  • Certain home building projects require construction permits. 
  • If a restaurant does not pass a health inspection, the inspectors can close it.  

Did you guess that all of these are true? If so, you are right! Each of these reflect rules and laws designed to keep people safe from things like car accidents, unstable structures, and foodborne illnesses. Another name for a rule or law is a mandate. 

Mandates in everyday life
While mandating something may sound like an uncommon occurrence, mandates are part of our everyday lives. Take the example of traffic laws. Speed limits are mandates designed to make drivers, passengers, and the people around them safer. While in certain rare circumstances it may be acceptable to significantly exceed the speed limit (e.g., an ambulance speeding to the hospital during a medical emergency), it is generally unacceptable and illegal to drive faster than the limit. Speed limits set a standard to prevent people from endangering themselves or others. Similarly, drivers and passengers are mandated to wear seatbelts. In the event of an accident, people are less likely to get severely injured or die if they are wearing a seatbelt. In this way, seatbelts improve the safety and health of everyone. Vaccine mandates are similar; they require that certain groups of people receive a vaccine to keep themselves from getting a disease and to prevent them from spreading it to others. As such, vaccine mandates also keep everyone safer and healthier.

Mandates are actually quite common for vaccinations, even if they aren’t always called by that name. Many schools and colleges require students to receive certain vaccines before they are allowed to attend classes. These requirements are designed to reduce the chance of infectious diseases spreading in classrooms. Not only does this keep students healthier, but it also protects their families because students are less likely to bring an infectious disease home. Similarly, many hospitals have employee mandates for the yearly influenza vaccine to not only keep their employees safe, but also their patients. 

Immunization mandates may also be implemented during outbreaks or pandemics because they can help stop the spread of a disease in a community or population. Typically, to effectively stop the spread of a disease, the population needs to reach “herd immunity.” Herd immunity, also called “community immunity,” is the percentage of the population that needs to be immune to a contagious infection to stop its ability to effectively spread from one person to another. Individuals can only become immune by having the illness or getting vaccinated. Since isolating all people with the disease involves far more resources than vaccination, vaccination is the preferred way to achieve herd immunity. However, getting most of the population vaccinated, particularly in a short amount of time, requires many individuals to work together to achieve the common goal. Unfortunately, some people within the group may not be able to be vaccinated. Others may simply choose not to be vaccinated. If enough people opt out of vaccination, herd immunity will not be achieved. If herd immunity is not reached, the disease will continue to spread, increasing the risk for everyone. As such, vaccine mandates may be needed to reach the necessary percentage to achieve community immunity.

While the science behind vaccine mandates is clear, they also provide an example of the complexity of science and society. Because some individuals may not want to get a vaccine, making a law requiring it may be viewed as limiting an individual’s freedom of choice—even though they are making this choice for others with whom they come in contact. Nonetheless, some people may determine that they are unlikely to get the disease, so they don’t want the vaccine. Or, they may be concerned about the vaccine’s safety, so they feel the risk of the vaccine is greater than the risk of the disease. They may have religious beliefs that the vaccine conflicts with, such as if a particular ingredient is included. Or, they may simply want the right to choose whether to get vaccinated. For these individuals, mandates will be more about their emotional and personal views than the science involved in protecting the public. 

Vaccine passports
In the same way that vaccine mandates may become emotionally charged, so, too, may something called “vaccine passports.” You may have heard of these during the COVID-19 pandemic. So, what are they and how do they relate to vaccine mandates? 

Vaccine passport is a term that refers to documentation or proof of vaccination. Such documentation would permit the holder to participate in activities that nonvaccinated individuals might not be allowed to.  Proof of vaccination is currently required for entry into countries where yellow fever is common. 

While deciding when and how to use COVID-19 vaccine passports may be complicated in a manner like implementing vaccine mandates, the logic behind these passports is straightforward. People who are immunized are much less likely to get or spread COVID-19 to other people. Because of this, a gathering of vaccinated people is likely to be safer than a gathering of unvaccinated people. As such, as businesses and event venues work to reopen, they will likely want to do so in a way that decreases the chance for people to get exposed to COVID-19. By asking visitors to show a vaccine passport, businesses can hold safer gatherings and help people understand the level of risk posed by attending an activity or event. The use of vaccine passports would likely vary in different situations. However, vaccine passports could be used as a tool to allow people to get back to activities and events more quickly and safely. They could be used in the same way proof of a negative coronavirus test has been required in certain situations during the COVID-19 pandemic.

While the term “vaccine passport” may be unfamiliar, many examples exist in our society where people must have documentation to legally participate in activities. For example, a driver’s license is required to operate an automobile. A passport is required to prove an individual’s identity and nationality when entering a foreign country. A birth certificate is required for school enrollment or to procure a marriage license. And proof of vaccination is required for school entry. Despite these existing uses, vaccine passports have caused concerns during the COVID-19 pandemic. It is not yet clear whether or how widely they will be implemented. 

Like other laws that protect people, vaccine mandates are designed to prevent the spread of infectious diseases in a population. Sometimes mandates are necessary to reach herd immunity if enough people do not voluntarily get vaccinated. Whether mandates will be needed for COVID-19 remains to be seen; however, as the country and the world tries to cautiously return to normalcy, vaccine passports and mandates could be tools that help us get through the pandemic. 

Think about it: 

  1. List two other examples of laws designed to keep people safe, and if you think the laws accomplish that goal. 
  2. Pick a community stakeholder and describe two or three reasons why they might support vaccine mandates or passports.
  3. The article lists examples of why some people object to vaccine mandates. List one or two other examples of objections you think people may have to vaccine mandates or vaccine passports. 
  4. Do you think an individual should have the freedom of choice to comply even if that choice could cause harm to another person? Why or why not? 

Related resources
Human Immune System: Types of Immunity, VEC 
Unit 2 Lesson 2: Discovery and Development of Vaccines, VMP  
        This lesson focuses on the different ways that people become immune to pathogens  
        and includes activities and resources related to herd immunity.

April 21  

How do we know the COVID-19 vaccines work? 

In the United States, there is a clear and comprehensive system of clinical trials in place. Clinical trials are studies that test a vaccine in phases, starting with small groups of healthy adults and eventually expanding to larger groups of many different types of people. This system helps ensure that a vaccine is safe and works before it can be approved and recommended for widespread use.

We talked about how we know vaccines are safe in the December 22, 2020 entry, “How do we know COVID-19 vaccines are safe?” In this entry, we will focus on how we know vaccines work by discussing two important terms, “vaccine efficacy” and “vaccine effectiveness.” 

Vaccine efficacy
The official term for how well a vaccine or treatment works in a clinical trial is known as “efficacy.” To test a vaccine, researchers conduct double-blind, placebo-controlled clinical trials. So, what does this mean?

  • Double-blind means that the study is set up such that neither the participants nor the researchers know who got the vaccine. This is important because it decreases the chance that people’s biases affect the results. For example, if a person knows they got a medicine, they might feel better than if they did not get it. Feeling better might be because the medicine worked, but it could also be because they know they had medicine. This is called a “placebo effect” because studies have shown that even people who get a placebo treatment sometimes feel better. 

    Since people in clinical trials need to report how they feel, double-blinding controls for the placebo effect. Likewise, the people running the study do not know who got the vaccine and who didn't, so that they do not inadvertently treat people in the two groups differently or interpret the side effects or experiences of participants differently.
  • Placebo-controlled means that study volunteers are randomly split into two groups. One group, called the experimental group, receives an injection of the vaccine being tested. The other group, called the control group, receives a placebo. The placebo is a benign substance that looks like and can be administered in the same way as the vaccine. In COVID-19 clinical trials the placebo was saline, which is a salt solution. You can see examples of other types of placebos in the “Phase III trials” part of this webpage

After the volunteers receive the vaccine or the placebo, they are monitored over time. Often, the participants are asked to keep notes about any health-related matters. That information helps researchers determine which side effects occur and how often, and they watch for any vaccine safety concerns. Researchers also monitor how many people get the disease during the trial. Scientists “break the code” to see who was in the vaccine group and who was in the placebo group after a pre-determined time interval or after a certain number of people become sick.

Below are two sample sets of vaccine trial data. In each case, 100 people got the vaccine and 100 people got placebo. In both examples, 30 of 100 people (or 30%) who received the placebo got the disease. We can use the data to tell us if the vaccine was effective.

 Example 1 –  Vaccine A
Vaccine A- clinical trial results table
In this example, 30 people who got vaccine A got sick and 70 remained healthy. This means 30% of the people who received vaccine got sick. When we compare this to the placebo, it is the same — 30% of the placebo group got sick. The lack of difference between the Vaccine A and placebo groups indicates that Vaccine A did not work. At this point, development of Vaccine A would likely stop because it did not offer any protection from disease.

Example 2 –  Vaccine B
Vaccine B- Clinical trial results table
In this example, 5 people who got Vaccine B became sick and 95 remained healthy, so 5% of the people who received the vaccine got sick. In the placebo group, 30% of the people got sick. The lower percentage of illness suggests that Vaccine B protected people against the disease over the time period of the study.

Using information like that shown in examples A and B, scientists can calculate vaccine efficacy. Vaccine efficacy is the percent reduction of disease in the clinical trial population following vaccination. To calculate this number, scientists use this equation:

Vaccine efficacy equation

Historically, a few vaccines have had the opposite of their intended effect and made people more susceptible to disease. The vaccine trials were stopped as soon as this was realized. This is why clinical trials are so important. They are designed to discover issues with a vaccine before it is approved for use by the public. For vaccines, clinical trials are big enough to detect major issues, but sometimes an issue will not become clear until millions of people have been vaccinated.

Vaccine effectiveness
In the above examples, we looked at vaccine efficacy, or how well the vaccine worked in the context of a clinical trial. However, a vaccine may not work as well when it is used in the real world. This is known as “vaccine effectiveness.” 

Watch a short video about the difference between vaccine efficacy and vaccine effectiveness.

Reasons for differences between efficacy and effectiveness can include: 

  • Differences between people who volunteered in the study and the general population, particularly because often in clinical trials people must meet certain criteria to participate.
  • Differences between conditions in the study and those in the real world. For example, the study population may have been limited to a certain age group that on average is younger than the age range of those receiving the vaccine in the real world. Since the immune system weakens over time, when older people use the vaccine, they may not be as well protected.
  • Greater variation in the dosing schedule in the real world. For example, in a clinical trial, participants are scheduled for their appointments according to the study protocol, but in the real world, people’s schedules vary greatly. People may miss appointments or not be available at the exact follow-up time, or the office may not have an appointment at the recommended time. The net result is that the timing during which doses of vaccine are given will likely be more variable.
  • Similarly, during vaccine trials only clinical sites that are approved to participate in the trial are giving the vaccine. Most often, this means a limited number of staff members are involved, and, therefore, vaccine storage, handling, and administration is fairly standardized. But, once a vaccine is being administered throughout the country, the number of locations and healthcare personnel handling the vaccine will be greater, and, therefore, more variability in storage, handling, and administration will naturally occur.  

Over time, scientists examine the data from real world conditions to determine a vaccine’s effectiveness and compare it to the efficacy. This helps them to better understand the vaccine and make sure it is working similarly to what would be expected based on the clinical trials.

The clinical trial process allows scientists to evaluate whether a vaccine is safe and works before it is distributed to the public at large. Clinical trials also give us a measurement to describe how well the vaccine works, called its efficacy. But, it is not until a vaccine is administered to the general population that we get a better understanding of how effective the vaccine is in real world conditions, called vaccine effectiveness. Both of these measures are important for scientists and public health officials working to keep people healthy.

Think about it: 

  1. Would you volunteer for a vaccine clinical trial? Why or why not? 
  2. If your job was to recruit volunteers for a vaccine clinical trial, what would be important for participants to know?  
  3. Can you think of other factors that might influence vaccine effectiveness in the real world? 
  4. Practice calculating vaccine efficacies. Worksheet | Answers   
  5. Do you think different vaccine efficacies might be acceptable based on circumstances? Explain your answer.

Related resources
Making Vaccines: Process of Vaccine Development, VEC
How do we know COVID-19 vaccines are safe?, VMP 
What Is the Difference between Vaccine Efficacy and Vaccine Effectiveness? (Video), VEC 

March 18  

What can teens expect when getting a COVID-19 vaccine? 
(Updated 6/15/2021)

Are you excited to get a COVID-19 vaccine? Maybe a bit nervous? People have different feelings about getting vaccines — and individuals even sometimes have different feelings about different vaccines. An array of feelings is normal, but sometimes it helps knowing what to expect. 

Teen vaccine eligibility
As of May 2021, three COVID-19 vaccines are authorized for use in the United States — Pfizer-BioNTech, Moderna, and Johnson & Johnson/Janssen. Of these, only the Pfizer vaccine is approved for ages 12 and older, with the other two vaccines currently approved for ages 18 and older. Clinical trials determined that the Pfizer vaccine is safe and works well in those 12 years and older. Clinical trials of the Moderna and Johnson & Johnson vaccines are underway for teens and children, and Pfizer is currently testing their vaccine in those younger than 12 years of age. 

Preparing to get the vaccine
Most immunization sites require appointments though some may have “walk-in” hours for eligible people to get vaccinated. This varies widely from state to state, so you should check how things are being done in your area if you are now eligible to be vaccinated. 

A few other considerations are important before going for a COVID-19 vaccine:

  • If you have a history of severe allergic reactions (i.e., you carry an “epi pen”), a compromised immune system, or a health condition that might interfere with getting the vaccine, check with your healthcare provider to figure out if you can get the COVID-19 vaccine. You may be able to get it, but need to take special precautions. For example, some people are recommended to wait for 30 minutes of observation instead of 15 minutes after getting the vaccine.
  • Unless you regularly take a pain-relieving medication prescribed by your doctor, it is not recommended to take a pain reliever (such as ibuprofen or acetaminophen) before vaccination. These types of medications may affect how well the vaccine works. However, it is important not to stop taking a medication prescribed by your doctor before getting the vaccine without first checking that it would be safe to do so.
  • You may go to a vaccination site in your community, a local pharmacy, or your doctor’s office to get the vaccine. This also depends on how your state is handling COVID-19 vaccine distribution.

What to expect when getting the vaccine
If you are going to get a COVID-19 vaccine, here is an idea of what you may experience:

  • Before you go to the immunization site, remember to wear a mask and plan to social distance the same way you would in any other public space during the pandemic. Wear clothing that makes it easy to access your upper arm without removing your shirt. Take any appointment confirmation, identification, or other items requested by the site. You may also want to take a book or your phone to pass time spent waiting. In some cases, you may be asked to read information about the vaccine and complete a form on the computer before you go to the appointment. 
  • When you arrive, you will most likely be asked to sign in or confirm your appointment and eligibility. The health care professionals at the site will probably ask you and your parent or guardian a few questions before you get the vaccine. For example, they may ask if you have any history of severe allergic reaction or if you are allergic to certain things.
  • After you are signed in, you may need to wait for your turn to get vaccinated. Waiting areas should be set up with social distancing measures to ensure everyone’s safety. 
  • When it is your turn, the person giving the vaccine may ask you a few more questions.  For example, they might confirm your name, ask in which arm you want the vaccine, or repeat questions about allergies or other vaccines. This repetition helps ensure that people are safely and appropriately vaccinated. It is particularly important at vaccination clinics where many people are coming and going. 
  • When the vaccine is administered, it does not take long and usually feels like a pinch. Many people find it helpful to distract themselves during the shot by looking at something across the room or talking to someone. If you feel nervous about getting the vaccine, you could also try listening to music or playing with an app to distract yourself. Other ways to decrease your nervousness and the “pinch” include taking a few slow, deep breaths as the vaccine is given, or ask for an alcohol pad to be rubbed on your opposite wrist shortly before the vaccine is administered. As the vaccine is given, blow on the area with the alcohol; you will feel the cool temperature of the alcohol evaporating more than the pinch of the shot.
  • After the shot is complete, you will most likely be asked to go to a waiting area. While the risk of an allergic reaction from a COVID-19 vaccine is very low, it makes sense for everyone to be observed after the injection as a safety precaution. People are asked to wait 15 to 30 minutes in case they have any allergic reactions to the vaccine. Although rare, these reactions can occur. They typically occur soon after getting the vaccine, which is why people are asked to wait. 
  • At some point during the appointment, you should receive a vaccination card that tells you which COVID-19 vaccine you received and the date you received it. Some people immediately take a picture of this card, so if it is misplaced, they still have the information. While it may be tempting to post a picture of your vaccination card on social media, it is not recommended to do so as the card may have personal information that should not be made public. Some vaccination sites have selfie stations or offer stickers that provide alternative ways to share your vaccination experience with your followers. 
  • Since the Pfizer vaccine is a two-dose vaccine, you may also be asked to sign up for a second appointment. The site will let you know the correct timing for your second injection. Many sites do the second appointment scheduling during the post-vaccine observation period.
  • You may also be asked if you are up to date on other vaccines, so that you can get those while you are getting the COVID-19 vaccine. But it is not clear if all vaccination sites will be offering this service. Teens may need vaccines such as Tdap, HPV, or meningococcal vaccines (one or both versions). Some may also need to catch up on vaccines typically given at younger ages, like MMR, hepatitis A, hepatitis B, polio, or chickenpox. While getting multiple vaccines may make you nervous, particularly if you don’t like shots, don’t let the possibility deter you from getting your COVID-19 vaccine. Remember, getting a vaccine is much faster and less painful than any of these diseases.

What to expect after getting the vaccine
Getting a COVID-19 vaccine is similar to other immunizations. Some people have side effects while others do not. Side effects are a sign that your body is responding to the vaccine, but don’t worry if you don’t have side effects — it doesn’t mean the vaccine didn’t work. People’s immune systems respond differently. The most common side effects are pain, redness or swelling at the injection site or tiredness, low-grade fever, or muscle aches for a day or two after getting the vaccine. For the mRNA vaccines, these side effects tend to be more common after the second dose. A very small number of young people, particularly males, have also experienced a condition called myocarditis. Myocarditis, or inflammation of the heart, is a condition that sometimes occurs after viral infections, including COVID-19. Current data indicate that the condition occurs within 4 days of dose 2 and affects about 1 in 50,000 people between 16-39 years of age. Symptoms may include chest pain, shortness of breath, or a fast heartbeat. If you experience these, or any other symptoms you are unsure of, tell a nearby adult or contact your health care provider. While this condition may sound scary – and be scary if you experience it – it is important to know that it typically goes away in a few days and does not cause permanent heart damage. The CDC is continuing to monitor the situation, but given the risks of the vaccine and the risks of the disease, which more often causes myocarditis, both the CDC and the American Heart Association recommend that eligible teens get the COVID-19 vaccine. 

To help scientists monitor vaccine side effects, your parent can sign up for V-Safe to report any side effects that you feel. V-safe is a vaccine monitoring program developed by the CDC. This program will send check-in text messages after each dose of vaccine to gather data on any side effects you may experience. This system helps with continuing to monitor vaccine safety, particularly in different groups of people. Individuals across the country have participated in the program. Hopefully, you will participate, too, so that scientists can gather information about the vaccine experience of young people. 

Immune responses develop a couple of weeks after getting the last dose. Right now, we know that most people who completed the full course of coronavirus vaccine are unlikely to get sick from COVID-19. However, we are still studying how long protection lasts. So far, we know it lasts for at least 6 months. Vaccinated individuals should continue to follow the guidance related to mask wearing and social distancing suggested by the CDC and local health authorities.
It may be different for people who are fully vaccinated, which occurs two weeks after getting the second dose. As more people get vaccinated, more restrictions will be lifted. For this reason, it is important that everyone who can get vaccinated do so — not only for themselves, but also for those around them and for the community at large.

Think about it: 

  1. Why do you think it is important to do vaccine clinical trials on teens and children rather than relying on the findings in adults?
  2. How do you think the experience of a teen receiving a vaccine would be different from that of a parent or other adult?

Related resources
Your COVID-19 Vaccine Appointment, CDC 
Age Groups and Vaccines: Teens/College, VEC 
Questions and Answers about COVID-19 vaccines, (includes more about myocarditis, including a short video),VEC
Myocarditis and Pericarditis Following mRNA COVID-19 Vaccination

Download a version of this article updated on 6.15.2021 [PDF, 164 KB]


March 10  

Will the COVID-19 vaccines work on the newer variants of coronavirus?    

Scientists hope the answer to the above question will be yes. So far, the limited data we have suggests that the current mRNA vaccines and the newer adenovirus-vector vaccine will be effective against most existing variants. Let’s review how viruses evolve and how vaccines work to understand why these variants are causing concern. 

How viruses evolve
Viruses that reproduce in people infiltrate human cells so they can use the cells’ machinery to replicate. Every time a virus reproduces in a cell, its genetic material is copied. During the copying process there is an opportunity for the virus to change or evolve. This can happen in one of two ways: 

  1. Mutation: A virus can change if a mistake occurs when the viral DNA or RNA is copied. For example, information can be left out or entered in the wrong place. RNA viruses tend to be “sloppy” and make mistakes during the copying process that result in mutations.  
  2. Recombination: A virus can change by sharing genetic material with another virus that has infected the cell at the same time. 

When a virus changes, the new version of the virus is called a variant. When the variant replicates, that mutation is also replicated. Sometimes, these new variant viruses have an advantage over previous versions. For example, the mutation might help the virus spread from one person to another more easily. When this happens, the variant with the advantageous mutation will be more likely to survive than older versions. In the case of SARS-CoV-2, the virus that causes COVID-19, recent variants have been in the news. Scientists are working to understand if these new versions of the virus are stopped by antibodies produced through vaccination. 

Watch this short animation about how coronaviruses evolve.

How a vaccine could stop working against a new variant 
First, let’s review how the current COVID-19 vaccines work. These vaccines train the body to recognize and neutralize the spike protein on the surface of the SARS-CoV-2 virus. As part of this immune system training, the body develops antibodies to the spike protein. These antibodies float around in the blood checking to find a protein that they can bind to. Wherever a protein match is found, the antibodies bind to them and prevent the virus from attaching to cells. 

Antibodies generated after vaccination might not be able to bind to the spike protein if the virus evolves in a way that changes the shape of the spike. In this manner, the variant virus will no longer be prevented from attaching to the person’s cells.  So, how can scientists tell if a new variant can evade existing antibodies?

Scientists can evaluate the ability of the vaccines to stop new variants in a few ways:

  1. Antibody studies – Scientists can combine antibodies from vaccinated people with new versions of the virus in the lab. They test to see if the antibodies can “neutralize” the virus or stop it from infecting cells. If the antibodies work in the lab, it is likely that they would also stop the virus from infecting vaccinated people in the community. It is important to recognize that while these studies are the fastest to do, they do not tell us everything we need to know. Antibodies are only one part of the body’s immune system defenses. Even if they do not completely neutralize the virus, other immune system components may still be able to protect a vaccinated person from getting sick. 
  2. “Real world” studies – Over time, scientists can monitor people who have been vaccinated or naturally infected. They check to see if they are becoming sick with the different variants despite the immunity that was generated by natural infection or vaccination. These studies are more challenging and expensive to do.

What happens if the vaccines don’t work against the variants?
If scientists find that vaccinated people are not protected against newer variants, they can revise existing vaccines to better match the variants. This is what is done each year for influenza. The influenza virus changes so rapidly that scientists need to make a new version each year. Hopefully, one day scientists will be able to create a so-called “universal” influenza vaccine — one that will protect against influenza no matter how much the virus changes. 

As with influenza, scientists are monitoring SARS-CoV-2 and the new COVID-19 vaccines. They are working to create revised vaccines in case the current ones become less effective. If this happens, people might need to get a booster dose. Or, if the virus continues to spread rapidly and change, people may need to get multiple booster or annual doses. Right now, scientists do not think people will need annual COVID-19 vaccines, but time will tell.

When viruses replicate, they often change. If those changes are advantageous, new versions, called variants, will become more common. As variants arise, they may also be able to evade immunity caused by previous infection or vaccination. In the case of SARS-CoV-2, current research suggests that the COVID-19 vaccines will continue to offer protection, but scientists will continue to monitor variants in case something changes.

Think about it:

  1. Based on the discussion above, how does the number of people who become infected affect the chance of a new variant forming? How do the number of variants affect the chance of needing to revise vaccines?
  2. If you were a public health professional, what would be your recommendation(s) for how society could avoid or decrease the opportunity for variants to develop? 
  3. If you were a scientist working on vaccine development, how would you prepare for the chance that variants might arise?
  4. If a variant formed that our current vaccines didn’t work against at all, what steps do you think would need to be taken to protect people from it?

Related resources
Biology of SARS-CoV-2: Evolution (Animation), HHMI BioInteractive 
Emerging SARS-CoV-2 Variants, CDC 
Unit 2 Lesson 2: Case Studies: Influenza and HIV, VMP  
This lesson focuses on the mechanisms by which viruses infect cells and replicate. The lesson also covers genetic processes by which viruses are able to circumvent immune system defenses.

February 16 

What is the difference in the immune response between vaccinated and unvaccinated people? 

Please take a few minutes to review this image and see what you can conclude from it before reading the rest of the passage.

vaccinated vs. unvaccinated graphic
Download this image [PDF, 130 KB]

Hopefully, you were able to tell that vaccination causes changes in our immune system’s response to a virus. But because often nothing noticeable happens when vaccinated people are exposed to a virus, sometimes it is difficult to know that vaccination made a difference. So, let’s consider the different immune system reactions of two people exposed to SARS-CoV-2, the virus that causes COVID-19:

  • Mr. Smith has not yet received his COVID-19 vaccine.
  • Ms. Jones received both recommended doses of the COVID-19 vaccine. She finished her last dose one month ago.

Mr. Smith and Ms. Jones are teachers at the same school. After a recent staff meeting, they find out that they were both exposed to COVID-19 when another teacher did not realize he was infected. 

Watch this short animation as a reminder of how a virus infects cells. 

Mr. Smith’s immune system response
(represented by the “No vaccination” part of the diagram)

When the virus attaches to Mr. Smith’s cells and starts reproducing, new virus particles are released from infected cells. These cells infect nearby cells to start the process over again. In the diagram above, these repetitive cycles of viral replication are demonstrated by the pink arrows. The increasing pink color shows that as these cycles repeat, more viral particles are available to continue the process. This increasing amount of virus makes it more difficult for Mr. Smith’s immune system to stop the infection.

In the early days of the infection, Mr. Smith’s innate immune response will be in charge because his body has not encountered the SARS-CoV-2 virus previously. This is shown in the blue circle in the diagram. It will take about 5 to 7 days before the innate immune response starts to get significant help from the adaptive immune system. 

The important difference between the innate and adaptive immune response is the method by which they respond to an infection. Innate immunity is non-specific; it is meant to be a first line of defense. On the other hand, adaptive immunity is specific, meaning its components have special training. In this case, adaptive immune system responses are targeted against the SARS-CoV-2 virus. As demonstrated by the green circle in the diagram, once the adaptive immune response starts, the immune system can more quickly control the infection. 

After about a week to ten days, Mr. Smith’s immune system gains control, and he feels better. Unfortunately, Mr. Smith’s wife is now feeling “under the weather,” even though Mr. Smith thought he did a good job of staying isolated while he was sick.

Ms. Jones’ immune system response
(represented by the “Vaccination” part of the diagram)

It is possible that Ms. Jones’ immune system will recognize the SARS-CoV-2 virus before it can get into any of her cells and begin replicating. If this happens, she will not have any symptoms and she will not be capable of spreading the virus to anyone else. But it is also possible that a few viral particles could still replicate before Ms. Jones’ immune system realizes that she has been exposed. As in Mr. Smith’s case, the pink arrows indicate viral replication. You can see that virus does not have as much opportunity to replicate in Ms. Jones’ cells.

This is because Ms. Jones has been vaccinated. The vaccination allowed her immune system to train specialized forces to recognize the SARS-CoV-2 virus. As a result, her adaptive immune response (represented by the green circle) is able to jump into action much more quickly (within 1 to 3 days) than Mr. Smith’s did. The result is that the innate immune response (represented by the blue circle) is in charge for much less time, and Ms. Jones’ infection is shut down much more quickly. If Ms. Jones feels sick at all, she will have fewer symptoms for fewer days.

Think about it: 

  1. What differences did vaccination make for Ms. Jones' experience? 
  2. If Mr. Smith is exposed to the SARS-CoV-2 virus in the future, what do you think his diagram would look like? Why?
  3. Watch the animation, "The Innate and Adaptive Immune Systems," and think about how the information in the animation relates to the diagram and the experiences of Mr. Smith and Ms. Jones, Be prepared to share your observations in a class discussion. 

February 1 

Why are they having trouble getting the vaccine to people who want it?

Getting COVID-19 vaccines to the public has been challenging in the early days after their approval, so let’s consider a few reasons why.

The vaccines
All vaccines must be transported and stored in a way that maintains their effectiveness.

Both COVID-19 mRNA vaccines are temperature sensitive: 

  • The Pfizer vaccine must be stored at -70 degrees Celsius (°C), which is much colder than the freezers that we use in our houses. In fact, this is even colder than the average temperature of central Antarctica. 
  • The Moderna vaccine can be stored at “warmer” temperatures of about -20°C. 

In addition to the temperature requirements, once these vaccines are thawed, they cannot be frozen again. And, once doses are taken out of the vial, the remaining doses must be used within a few hours.

These requirements mean that a lot of planning needs to go into vaccine transport, storage and use.  

The supply
The number of people who want to get the COVID-19 vaccine is extremely high. And, in order to stop transmission of this virus in our communities, millions and millions of people will need to be vaccinated. 

On the other hand, COVID-19 vaccines are new. Because of the pandemic, production of the vaccines was allowed to start during the clinical trials to save time. If the vaccines did not work or were not safe, they would have been thrown away. Luckily, that did not happen with the mRNA vaccines. But, even with the faster production schedule, it will still take time to make enough doses of these vaccines to immunize the majority of people in this country and around the world.

In sum, the number of people who want the vaccine combined with the fact that these are new vaccines creates a big gap between supply and demand. 

The situation
Everything is more difficult in a pandemic. We cannot do things in the way we would typically do them. For example, normally when people want something, they wait in line for it. But, because of social distancing to try to slow the spread of the virus, this is not an option. And, some of the things that might be done in the summer, like moving people outside and spreading them out, are not possible when the weather is cold and unpredictable. Even though there are some ways to work around these issues, the fact remains that the risk of spreading COVID-19 itself makes organizing vaccine clinics more challenging.

The distribution plan
One of the biggest challenges has been that there has not been one centralized plan for administering vaccines. Plans for distributing the vaccine vary from state to state and sometimes even from county to county. While this makes sense in some ways because different places have different situations, a single general approach that varies in minor ways would be less confusing to the public and easier for those in charge of distribution.  

Another aspect of the distribution plan is its sheer size. Millions and millions of people are waiting to get a COVID-19 vaccine. People working on distribution are trying to make sure not only that a lot of people get vaccinated, but also that the vaccine distribution is equitable for people with different backgrounds and situations all over the country. In an attempt to address this, the Centers for Disease Control and Prevention (CDC) made recommendations regarding vaccine prioritization. 

While the CDC recommendations offer guidelines, it is up to each state to decide how to allocate the vaccines they receive. So, people living in one state might have different eligibility and prioritization schedules than family and friends living in another state.

Just because something is challenging doesn’t mean that it can’t be done. But it does mean that it will take hard work, creativity, and some patience.

Think about it:

  1. If you were in charge of COVID-19 vaccine delivery for your town/city, how would you do it? 
        a. How would you decide who gets the limited doses?
        b. How would you have people schedule their appointments? 
        c. Where would you hold vaccine clinics? 
        d. How would you set up the clinics to keep everyone safe and ensure that you
            have enough people, so that you don’t waste any doses of vaccine?
  2. What are some of the advantages of having local areas organize their own vaccine administration? What are some disadvantages?
  3. If someone gave you the chance to help decide who would get immunized first, would you want to be part of that team? 
  4. Choose 2 state health department websites and review the COVID-19 vaccine distribution information. How are their approaches similar? How are they different?

Related resources:
When Vaccine is Limited, Who Should Get Vaccinated First?, CDC 
Pfizer-BioNTech COVID-19 Vaccine Storage and Handling Summary, CDC
Moderna COVID-19 Vaccine Storage and Handling Summary, CDC 


January 14 

What are the side effects of the COVID-19 mRNA vaccines? 

  • Side effect: An effect that occurs after receipt of a medication or vaccine. Even though these are unwanted, they can be expected based on previous experience (e.g., clinical trials) and result despite proper use of the medication or vaccine.
  • Adverse effect: An unexpected effect that occurs after receipt of a medication or vaccine, which may or may not be caused by the medication or vaccine.

Watch this short video to learn more about the differences between side effects and adverse effects.

Side effects after COVID-19 mRNA vaccines 
People are sometimes surprised when they have a side effect following a vaccine or medication, and they may perceive these effects as problematic. But, side effects do not mean there is a problem. For example, the two new mRNA COVID-19 vaccines have resulted in side effects, such as: 

  • sore arm (at injection site)
  • tiredness 
  • headache
  • muscle or joint aches
  • fever or chills

These side effects typically occur in the first few days after receiving the vaccine, and in the case of both new mRNA COVID-19 vaccines, the side effects were more likely after the second dose. Further, younger people were more likely to experience side effects than older people. So, why does this happen and what does it mean related to the COVID-19 mRNA vaccines?

  1. In some cases, side effects indicate that your immune system is working to defend against the vaccine. Side effects are often part of the immune response generated by our bodies. For example, aches and pains result from changes that we can’t see, like swelling, as immune system cells move into the area where a “foreign invader” has been identified. Redness can result from increased blood flow to the area of the immune response, and fever is the body “turning up the temperature” to increase the effectiveness of the immune system and decrease the effectiveness of a perceived pathogen. As you might have realized, many side effects are things we describe as symptoms when we are sick, but in that case, too, it is our immune system responding to a “foreign invader.”
  2. Side effects occur in the first day or two after the vaccine because the immune system is working. After a vaccine is administered, it takes several hours for the immune response to “ramp up” and respond to what it perceives as a “foreign invader.” Often, the first effects will be closest to the injection site, like pain and redness at the site of the injection, with later effects being further from the injection site or widespread, like fever.
  3. The greater number of side effects after the second dose and among younger recipients suggest that mRNA vaccines invoke strong immune responses. So, even though side effects might make you “feel sick,” you aren’t actually infected. Your immune system is just responding to the vaccine. Like a fire drill, the COVID-19 vaccine trains your body to protect you from SARS-CoV-2 if you are exposed to it in the future. 

Adverse events after COVID-19 mRNA vaccines
So far, one adverse event following COVID-19 mRNA vaccines has been identified. Specifically, a small number of people have had severe allergic reactions, called anaphylaxis. Currently, it is estimated that this severe allergic reaction has occurred in about 11 of every 1 million people who got the vaccine. Because these types of allergic reactions tend to occur very quickly after someone gets the vaccine, people are being advised to stay at the site where the injection was given for 15 to 30 minutes after getting vaccinated. No one has died from this reaction. Likewise, scientists and public health experts have systems in place to learn more about these reactions as well as monitor for other adverse events on an ongoing basis.

Think about it: 

  1. Do you think some people might confuse side effects with actual illness? Why or why not? 
  2. Why do you think some people experience side effects, but others do not? 
  3. If a person experienced a physical condition in the days after receiving a vaccine, like indigestion or a racing heart, do you think they might believe the vaccine was the cause even if the evidence proved otherwise? Why or why not? 

Related resources
Unit 1, Lesson 2 – The Innate Immune Response 
What to Expect after Getting a COVID-19 Vaccine, CDC
Side Effects and COVID-19 Vaccines: What to Expect, John Hopkins Bloomberg School of Public Health

To see the archive of questions from 2020, please visit the Archived Coronavirus Pandemic Questions page