COVID-19 Vaccine FAQ
We have created a list of common questions about the COVID-19 vaccines based on current knowledge and understanding. These questions will continue to evolve with time, so we encourage you to check back frequently for the most up-to-date information.
Who is currently eligible for the COVID-19 vaccine?
Individuals 5 years and older are currently eligible to receive the two-dose Pfizer COVID-19 vaccine, while those 18 years and older can receive the two-dose Moderna or single-dose Janssen vaccine.
The vaccine was produced very quickly. How do I know it is safe?
The U.S. vaccine safety system ensures that all vaccines are as safe as possible. Today, more than 200 million people in the U.S. have received at least one dose of the vaccine and experienced only minimal side effects, further underscoring the safety of the COVID-19 vaccines. Despite what the vaccine project name may suggest, “Operation Warp Speed” does not mean that manufacturers were able to skip steps or cut corners in the vaccine development process. Instead, after development of the vaccine, manufacturers took a secured risk and overlapped the study, manufacturing and distribution phases. The FDA committed to giving these vaccinations priority (not rushed) review at all phases of the studies, which helped speed up the overall process. Ongoing monitoring of vaccine effectiveness and side effect reports will continue to be evaluated by the FDA and the manufacturers.
If I get the COVID-19 vaccine, should I still wear a mask?
Yes. For several reasons, a mask and other proven methods of preventing COVID-19 (hand hygiene and social distancing) are still important even after receiving the vaccine. It typically takes a few weeks for the body to build immunity after vaccination. That means it is possible that a person could be infected with the virus that causes COVID-19 just before or just after vaccination. This is because the vaccine has not had enough time to provide protection. Also, while the vaccines protect you from becoming ill, it is not yet known if the vaccines prevent you from spreading the virus if infected.
In addition, while COVID-19 vaccines are highly effective, there is a small percentage of people who might not be protected while the virus continues to spread – including those with compromised immune systems due to cancer and cancer treatments and those who are unable to be vaccinated due to severe allergic reactions to vaccine ingredients.
Masks also help protect against new strains of the virus, for which vaccine effectiveness is still unclear. For these reasons, it is important to continue practicing safety measures like wearing masks until vaccines are widely administered and the virus is no longer spreading.
If I have already had COVID-19 and recovered, should I still get the COVID-19 vaccine when it is available?
Yes, at this time the vaccine is recommended even if you previously tested positive for COVID-19. Due to the severe health risks associated with COVID-19 and the fact that re-infection with COVID-19 is possible, individuals who have previously been infected with COVID-19 should proceed with getting the vaccine.
Can you contract COVID-19 by getting the vaccine?
No. The vaccine is NOT a live vaccine, and it is NOT possible to contract COVID-19 from receiving the vaccine. Some people experience side effects from the vaccine, such as headache, muscle pain, or fever – but that does not mean you have COVID-19. It means your body is working to build the necessary immunity against the virus, which is a good thing.
How many doses are required? If multiple, when do I get another dose?
The dose regimen for full vaccination will depend on the type of vaccine you receive. For both the Pfizer and Moderna vaccine, two doses are required. The second dose of the Pfizer vaccine should be administered 21 days after the first dose. The second dose of the Moderna vaccine should be administered 28 days after the first dose. It is very important to note that the second dose must be from the same manufacturer as the first dose. The Johnson & Johnson (Janssen) vaccine requires only one dose.
What should I do if I am unable to get the second dose exactly 21 days (Pfizer) or 28 days (Moderna) after the first dose?
While it is recommended that you receive the second dose as soon as feasible after day 21 or day 28, we understand that it might not be possible to receive it on the desired date. This could be due to multiple reasons. Please keep the following in mind if you cannot receive the second vaccine dose on the desired date:
1. It is strongly preferred that you receive the second dose from the same manufacturer as the first dose. However:
- In exceptional situations in which the Pfizer or Moderna vaccine product given for the first dose cannot be determined or is no longer available, any available mRNA (Pfizer or Moderna) COVID-19 vaccine may be administered at a minimum interval of 28 days between doses to complete the vaccination series.
- In situations where the same Pfizer or Moderna vaccine product is temporarily unavailable for an individual’s second dose, it is preferable to delay the second dose (up to 6 weeks) to receive the same product than to receive a mixed series using a different product.
2. Get the second dose as soon as possible after the desired date has passed, as it is better to get the second dose late than not at all. You will still experience the same efficacy in the long run, although you may not see the full effect of the immunity until a few weeks after the second dose.
How long after receiving my full dose regimen until it is considered effective?
Similar to the flu vaccine, it typically takes a few weeks for the body to build immunity after vaccination. That means it’s possible a person could be infected with the virus that causes COVID-19 just before or just after vaccination and get sick. This is because the vaccine has not had enough time to provide protection. As a general rule, the vaccine is considered effective about two weeks after your full dose regimen, according to the manufacturers. If you are receiving the Pfizer or Moderna vaccines, which require two doses, there is evidence that the first dose will begin providing some immunity, but it is still very important to receive the second dose for optimal results.
Can I choose which vaccine I get?
In general, we do not recommend waiting for a specific manufacturer, but your age and health history must be carefully considered before deciding which vaccine is right for you, as some may have increased risks. All FDA-approved or FDA-authorized COVID-19 vaccines have been proven effective in reducing the risk of becoming infected with the SARS-CoV-2 virus that causes COVID-19, decreasing the likelihood of having a severe case of the illness and reducing hospitalizations and deaths due to COVID-19 disease. Early defense is better than no defense against COVID-19. Talk to your doctor to determine the most appropriate vaccine for you.
If receiving a two-dose regimen, should those who experience significant side effects from their first COVID-19 vaccine dose expect significant or worse side effects with the second dose? What about those who were previously COVID-19-positive?
Based on data from the Pfizer and Moderna vaccines, there appears to be an increased incidence of experiencing certain side effects from the second dose of the COVID-19 vaccine compared to the first dose (e.g., fever, fatigue, headache, chills, muscle pain, and joint pain). This does not mean that all vaccine recipients will experience these side effects with the first or second dose. A full list of the reported side effects comparing Dose 1 and Dose 2 may be found within the Pfizer BioNTech EUA Fact Sheet and the Moderna EUA Fact Sheet.
At this time, we do not have definitive data to state whether vaccine side effects are worse in patients who were previously positive for COVID-19.
How long will I need to be observed after I get the vaccine?
In general, a 30-minute observation period is recommended for anyone with a history of severe allergic reactions (due to any cause), and a 15-minute observation period is recommended for all other individuals.
Will the COVID-19 vaccine result in a false positive COVID-19 test?
No, COVID-19 vaccination will not cause a false positive COVID-19 viral test. Per CDC guidance, the immunity response from a COVID-19 vaccine could possibly result in a positive antibody test, which indicates previous infection and potential protection against the virus.
If I become COVID-19-positive following my first dose of the vaccine, should I take the second dose?
Per CDC guidance, you may receive the vaccine (either dose) following resolution of symptoms, if any, and completion of the quarantine period.
What ingredients are included in the COVID-19 vaccines?
Ingredients for authorized COVID-19 vaccines can be found via this CDC link. Individuals with allergies to any of the vaccine components should discuss concerns with their healthcare provider before receiving the vaccine.
Can the COVID-19 vaccine be administered to children?
The Pfizer COVID-19 vaccine is recommended for those ages 5 and over.
Is there a COVID-19 vaccine available for children younger than 5 years old?
Currently, 5 years old is the youngest age threshold for receiving the COVID-19 vaccine based on current studies. This age requirement could eventually be adjusted to include younger children as research and clinical trials continue. To date, the Pfizer-BioNTech COVID-19 vaccine is the only vaccine that has been authorized for use in individuals ages 5 and older.
Can the COVID-19 vaccine be administered to pregnant women?
COVID-19 vaccination is recommended for all people aged 5 years and older, including people who are pregnant, lactating, trying to get pregnant now, or might become pregnant in the future. Any of the currently FDA-approved or FDA-authorized COVID-19 vaccines can be administered to people in these groups; ACIP does not state a product preference. However, all women aged <50 years should be aware of the rare risk of TTS after receipt of the Janssen COVID-19 vaccine and the availability of other currently FDA-approved or FDA-authorized COVID-19 vaccines (i.e., mRNA vaccines) for which this risk has not been seen. See also People with a history of thrombosis or risk factors for thrombosis. There is no evidence that any of the COVID-19 vaccines affect current or future fertility.
I’ve read that fertility could be impacted by the COVID-19 vaccine. Is that true?
There has been no demonstrated link between vaccines and infertility in the studies conducted to date. The CDC reports there is no evidence that the COVID-19 vaccines cause fertility problems, and the American College of Obstetricians and Gynecologists states that the vaccine studies do not indicate any safety concerns for those who are pregnant or want to become pregnant.
What does it mean that the Pfizer COVID-19 vaccine has received full approval from the Food and Drug Administration (FDA)?
Receiving full approval means the Pfizer vaccine now carries the FDA's strongest endorsement of safety and effectiveness. This is based on thorough research and comprehensive data review over many, many months. You can read more about the Pfizer vaccine receiving full FDA approval here.
Why is a third dose of the COVID-19 vaccine necessary? Is it not as effective as we thought?
COVID-19 vaccines have been proven safe and highly effective, even against the Delta variant. The CDC’s Advisory Committee on Immunization Practices (ACIP) now recommends an additional dose of the mRNA COVID-19 vaccines (Pfizer and Moderna) specifically for people who are moderately to severely immunocompromised. A third dose will help this vulnerable population enhance their immune response and further protect them from serious – and potentially prolonged – illness. You can read more about the third dose for immunocompromised individuals here.