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Experts answer your questions: COVID-19 Vaccine


If you are eligible for a COVID-19 vaccine, visit our COVID-19 Vaccine website to schedule a vaccine. Please note if there is no availability, please check back later. New times will appear as they become available. Please be patient as we try to accommodate a large volume of requests.


This has been a stressful time for many people, yet access to new vaccines is an important and exciting step in our fight against COVID-19 and returning to a more normal way of life. To help address your questions about the vaccines that are now available to people, here are some facts from Tufts Medical Center’s Infectious Diseases doctors.

1. What COVID-19 vaccines are now authorized for people in the United States?

Three vaccines have received Emergency Use Authorization (EUA) from the Food and Drug Administration. Vaccines from Moderna and Pfizer received authorization in December 2020 and a vaccine by Johnson & Johnson (Janssen) received EUA in late February 2021. All three vaccines are offered at Wellforce vaccination sites.

2. How effective are the vaccines?

All three vaccines are extremely effective, exceeding all expectations and FDA benchmarks for success. In clinical trials, there were no deaths from COVID-19 among any participants who received vaccine.

3. Do the three vaccines work the same?

All three vaccines involve the use of “instructions” for your cells on how to make the “spike protein” that is unique to the virus that causes COVID-19. The “spike protein” produced by your cells after vaccination makes your immune system “think” your body really has COVID-19 even though it doesn’t. This causes the immune system to produce antibodies that attach to the spike protein on the actual virus causing COVID-19 in case you are exposed and stops infection. The Moderna and Pfizer vaccines do this by introducing a blueprint called mRNA in a specially designed particle. The Johnson & Johnson (Janssen) vaccine does this by introducing a recipe called DNA which is carried by an inactivated version of another virus, an adenovirus. The adenovirus cannot multiply in the human body. The mRNA and DNA cannot integrate into the human genetic material.

4. Moderna and Pfizer vaccines require two shots. If I receive the Moderna or Pfizer vaccine, do I need to receive both doses of the vaccine for it to be most effective?

Yes. Both the Pfizer and Moderna vaccines are given to people in two doses, 21 (Pfizer) or 28 (Moderna) days apart. The effectiveness of the vaccines has only been studied in clinical trials after two doses.

5. Can I choose which vaccine to get? Should I try to get one vaccine over another because of their effectiveness rates or side effects?

All of the vaccines are highly effective in all populations studied, so there are no reasons to choose one over another. There will not be an option to choose the type of vaccine you receive at our vaccination locations.

6. Can I get COVID-19 disease from the vaccine?

No. You cannot develop COVID-19 disease from any of the vaccines.

7. Is it safe to get the COVID-19 vaccine?

Yes, the COVID-19 vaccines available — Pfizer, Moderna and Johnson & Johnson (Janssen) — have been thoroughly tested as part of clinical trials. The Food and Drug Administration (FDA) and a group of vaccine experts from throughout the country carefully reviewed information. The FDA then decided it was safe to make the Moderna and Johnson & Johnson (Janssen) vaccines available to persons aged 18 years and older. The Pfizer vaccine can be used in people 16 years and older. The lower age limits differ not because of safety concerns but because of different age cutoffs used in each study.

8. The vaccines were developed so quickly. Are we sure they are safe?

The FDA’s review of the vaccines was thorough and rigorous, and no steps were skipped in the process to review the safety of the vaccines. The FDA decided that the vaccines met safety and efficacy standards based on the currently available data from more than 70,000 diverse volunteers, and it was felt the benefits of the vaccines far outweighed the risk of any known side effects. More importantly, over 76 million Americans have now been vaccinated, with close monitoring of adverse events by the FDA and the CDC. No worrisome trends regarding safety have been found.

9. I heard there were side effects after people received the vaccine. What do we know about that?

The most commonly reported side effects for all COVID-19 vaccines are soreness at the site of the injection as well as flu-like symptoms, including fatigue, body aches, chills or fevers after the vaccine. For Pfizer and Moderna, side effects were most common after the second dose of the vaccine, and more likely to be experienced by younger people. These symptoms go away within the first few days after receiving the vaccine. The side effects tell us that the body is building protection against the virus.

10. What about allergic reactions due to the vaccine?

To date, people who have had allergic reactions to the vaccine have all recovered quickly. The risk of allergic reaction is very small and is similar to the risk of allergic reaction associated with all other medications and vaccines.

11. Do I need to receive a COVID-19 vaccine if I have been previously infected with COVID-19?

Yes. The CDC recommends that even people, previously infected with COVID-19, be vaccinated when eligible. This is because the immunity from vaccination appears to be more reliable than the immunity from natural infection. You can choose to delay your vaccination until 90 days after your infection, because you can be fairly confident your immunity from the infection will last that long. However, if you are eligible and want to be vaccinated sooner, you may. Please wait until you have been released from isolation from your COVID-19 infection before going to a
vaccination site.

12. If I receive the Pfizer or Moderna vaccine and I test positive for COVID-19 between dose 1 and dose 2, should I still get dose 2?

Yes. We simply ask that you delay your vaccination until you are released from isolation, so that you are no longer contagious to others. Please schedule dose 2 for as soon as possible after your release from isolation and as long as it is at least 21 days after the first dose of Pfizer vaccine or at least 28 days after the first dose of the Moderna vaccine.

13. Can I get the COVID-19 vaccine if I am pregnant?

Yes. Pregnant individuals are at a higher risk of getting severe COVID-19. For this reason, the CDC, Society for Maternal-Fetal Medicine and American College of Obstetricians and Gynecologists strongly recommend that pregnant individuals have access to COVID-19 vaccines and that each person has a discussion with their health care professional about their own personal choice.

You can find more information about COVID-19 vaccines and pregnancy here.

14. Can I receive the vaccine if I am breastfeeding?

Yes. The CDC and the Society for Maternal-Fetal Medicine report that there is no reason to believe that the vaccine affects the safety of breastmilk. You can find more information here.

15. Do the vaccines carry the same precaution/allergy statements?

No, the precautions/allergy statements are different for each vaccine. People who have a known allergy to Polyethylene Glycol (PEG) should not receive the Pfizer or Moderna vaccine. People who have a known allergy to polysorbate should not receive the Johnson & Johnson (Janssen) vaccine. If you have had a severe or immediate allergic reaction to a prior dose of the Moderna or
Pfizer vaccine, you can receive the Johnson & Johnson (Janssen) vaccine as your second dose. It’s important to discuss this with your primary care physician.

Other types of allergy histories, such as an immediate allergic reaction to another vaccine or injectable therapy, or a history of anaphylaxis due to any cause are considered by the CDC to be a precaution. People who have these reactions should receive the vaccines, but should be observed for 30 minutes (rather than 15) after each dose of vaccine. Allergic reactions (including severe allergic reactions) not related to vaccines or injectable therapies (e.g., allergic reactions to food, pet, venom, environmental or latex allergies. or oral medications including the oral equivalents of injectable medications) are not a contraindication or precaution to vaccination with COVID-19 vaccines. For more information, see CDC Vaccines & Immunizations.

16. Can I take the vaccine if I already take other oral medications (anti-anxiety/depression/home medications and antibiotics)?

Yes. There are no known reactions or interactions between oral medications and the vaccines.

17. When I get the vaccine, do I need to continue wearing masks, social distancing, etc.?

Yes. While we know the vaccine prevents you from getting COVID-19 disease, and protects others from getting COVID-19 from you, in public places we still must follow all of the rules including keeping social distance, wearing masks and following other CDC guidelines to reduce the risk of transmission. Over time and as more people are vaccinated, we expect that restrictions will gradually loosen.

18. If I still have to do all of those things, why should I get vaccinated then?

Ending a pandemic requires using all of the tools we have available. Together, the vaccine and these recommendations give us the best chance of protecting ourselves and others from COVID-19 and helping to slow its spread in our communities. Vaccination is the best tool we have for returning to the activities we love and miss.

19. Do the vaccines protect against asymptomatic infection and against vaccinated people from spreading the virus?

Yes. Studies show that the vaccines are extremely effective at preventing COVID-19 illness in vaccinated people. Early data also suggest that the vaccines are in fact very effective at preventing asymptomatic infection too (likely between 75% and 90%) and that when vaccinated people do develop infection, the amount of virus carried in their secretions is lower. Overall, this means that vaccines likely protect not just you but others.

20. How will I know when I am eligible to get the vaccine?

The state Department of Public Health has issued guidelines for when individuals can be vaccinated. People in Phase 1 and Phase 2 groups can get a vaccine now. You can find more details about when and where to be vaccinated here.

21. I saw information on Facebook/Twitter/Instagram that made me nervous about the vaccine. Where can I find the most accurate information?

Social media can easily and quickly spread information, including false information. It is always important to check the source of information. The CDC has provided excellent and trusted resources for questions about the current COVID-19 vaccines here; information from the FDA in multiple languages can be found here and is also very helpful. Your doctor can also talk to you more
about the vaccine. Please visit for videos and other information in multiple languages.

22. Are we allowed to travel internationally after receiving the vaccine?

Because the U.S. is still seeing high levels of COVID-19 activity, national and state public health experts continue to encourage Americans to avoid both domestic and foreign travel. The CDC has recently offered new travel guidance for vaccinated individuals here. Some U.S. states have adjusted their travel restrictions. Check the guidelines for the state you are visiting.
Also check here for the latest travel guidelines from the state of Massachusetts.

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