Why are COVID-19 boosters and third doses necessary?

Editor’s note: As what we know about COVID-19 evolves, so could the information in this story. Find our most recent COVID-19 blog posts here, and learn the latest in COVID-19 prevention at the Centers for Disease Control and Prevention. 

When the COVID-19 vaccine was developed, we knew we were likely going to need to administer “booster” vaccines — that is, another injection to help COVID-19 immunity last longer.

We also knew that some people with compromised immune systems wouldn’t be able to produce as many antibodies to COVID-19 after typical vaccination. This is true of many vaccines — people who, for example, have received an organ transplant, are undergoing chemotherapy, have advanced HIV/AIDS or take immune-suppressing medication won’t be able to create the immunologic response to vaccines to build adequate protection against disease. Thus, a third dose of the vaccine would benefit them.

The difference between boosters and third doses

The FDA currently recommends that people who are significantly immunocompromised receive a third dose of the COVID-19 mRNA vaccines currently approved by the FDA (Pfizer, which has full FDA approval, and Moderna, which has emergency use authorization). 

In accordance with the FDA’s recommendation and that of the CDC’s Advisory Committee on Immunization Practice (ACIP), The Ohio State University Wexner Medical Center is currently providing third-dose vaccines to eligible immunocompromised people.

A booster shot of the COVID-19 vaccine is different from what’s currently labeled a “third dose” only because of the difference in eligibility and timing.

A booster refers to a dose of a vaccine given to someone who did likely build enough protection initially when they received vaccination, but who may have lost some of that protection over time. It’s called waning immunity, and it’s something scientists and health officials expected to happen with COVID-19 vaccines.

Who is eligible for booster doses?

Boosters of the Pfizer COVID-19 vaccine are now approved by the FDA and CDC for people who have received both doses of the Pfizer vaccine and received the second dose at least six months ago. The FDA and CDC are still reviewing data from the Moderna and Johnson & Johnson vaccines to determine whether and how they would recommend boosters for people who initially received those vaccines. 

Eligibility standards are set by the CDC, FDA and Ohio Department of Health (ODH). In general, patients who are 65 and older, as well as anyone over 50 with certain underlying medical conditions should receive a booster vaccine. View specific eligibility for third dose vaccines and booster vaccines

Where can I get a booster shot?

Pfizer boosters are currently available at several Ohio State Wexner Medical Center locations as well as many other clinics and retail pharmacies. Learn more about how to schedule and who is currently eligible for COVID-19 booster vaccines

Does this mean the COVID-19 vaccines aren’t working?

No — data shows that the available COVID-19 vaccines are working effectively to prevent severe cases of COVID-19, hospitalization and death. But we’re seeing some waning protection, as was expected, and booster shots and third doses can help vaccinated people keep that protection longer.

Booster shots are common for many vaccines. The hepatitis B and shingles vaccines, for example, require boosters to achieve optimal immunity. 

Do I get a booster if I received the Moderna or Johnson & Johnson vaccine?

At this time, there’s no additional dose recommendation for the Johnson & Johnson or Moderna vaccines, except for immunocrompromised patients who received a Moderna vaccine. The J&J vaccine was given FDA emergency use authorization (EUA) in March 2020 — three months after mRNA vaccines received EUA. Because of this, J&J vaccine data is three months behind the mRNA vaccines, and an FDA decision on a J&J booster will likely be delayed for a few months.

Should my third dose or booster dose be the same brand as my previous doses?

While the recommendation may change as the FDA and CDC finish their reviews of available data, it’s recommended to receive the same booster dose of your original vaccine series.  

Robert Weber is the administrator of Pharmaceutical Services at The Ohio State University Wexner Medical Center and an assistant dean in the Ohio State College of Pharmacy.