Booster Shots and Third Doses for COVID-19 Vaccines: What You Need to Know
Lisa Maragakis, M.D., M.P.H., senior director of infection prevention, and Gabor Kelen, M.D., director of the Johns Hopkins Office of Critical Event Preparedness and Response, explain what you need to know about third vaccine doses and COVID boosters. While both kinds of shots are additional doses of the mRNA COVID-19 vaccines (Pfizer and Moderna), they have different purposes and are intended for different groups of people.
What is a COVID-19 vaccine booster?
A COVID booster shot is an additional dose of a vaccine given after the protection provided by the original shot(s) has begun to decrease over time. Typically, you would get a booster after the immunity from the initial dose(s) naturally starts to wane. The booster is designed to help people maintain their level of immunity for longer.
What is a third dose of the coronavirus vaccine?
A third dose of the mRNA COVID-19 vaccines (Pfizer or Moderna) is identical to the first two doses. It can help protect people with weakened immune systems who did not have a strong enough response to the first two doses of one of the mRNA vaccines. Such people can get a third dose as soon as 28 days after a second dose. The FDA has authorized, and the CDC recommends, that those with certain medical conditions that suppress the immune system get a third dose of the same brand of COVID-19 vaccine that they initially received.
Who can get a third dose of a COVID-19 vaccine?
Based on CDC recommendations, third vaccine doses are available now for people who are considered moderately or severely immunosuppressed. These would include those who:
- Receive active cancer treatment for tumors or cancers of the blood.
- Received an organ transplant and are taking medicine to suppress the immune system.
- Have either had a stem cell transplant within the last two years or are taking medicine to suppress the immune system.
- Were diagnosed with DiGeorge syndrome or Wiskott-Aldrich syndrome.
- Are diagnosed with HIV and have a high viral load or low CD4 count, or are not currently taking medication to treat HIV.
- Are taking drugs such as high-dose steroids or other medications that may cause severe suppression of the immune system.
If you are not sure whether you fit into any of these categories, please contact your medical provider.
When can I get a third dose of COVID-19 vaccine?
People who have an eligible medical condition that causes a suppressed immune system can receive a third dose of either the Moderna or Pfizer vaccine as soon as 28 days after the second dose. Johns Hopkins Medicine is offering a third dose to those who are eligible.
Why is a third shot of a COVID-19 vaccine needed?
The CDC recommends a third dose of the two-shot vaccines (Pfizer and Moderna) for people with certain health conditions to help further protect them from getting severely ill or dying due to COVID-19. Some people have conditions or take specific medication doses that can cause them to have a decreased immune system. Data suggest that two doses of the mRNA COVID-19 vaccine may not have a strong enough response in these individuals, and that they may benefit from a third dose.
How do I know if I need a third dose of COVID-19 vaccine?
If you are unsure about whether your health condition or treatment affects your immune system, discuss it with your health care provider, who can help determine if you would benefit from a third dose of COVID-19 vaccine.
Would a third COVID shot have to be the same brand of vaccine I got originally?
Ideally, yes: Your third vaccine dose should be the same type (Pfizer or Moderna) you received when you were first vaccinated. The third shot can be given to you when it has been at least four weeks (28 days) since your second shot, if you are considered immunosuppressed based on the criteria determined by the CDC.
Can I get an additional COVID-19 shot if I received the Johnson & Johnson vaccine?
Data are still emerging as to whether an additional dose is necessary for individuals who received the Johnson & Johnson COVID-19 vaccine. There is no current recommendation for an extra dose for people who received the Johnson & Johnson COVID-19 vaccine, even if they have a qualifying medical condition. Watch for information from the CDC.
Get information and updates from Johns Hopkins Medicine.