Skip to Main Content
Skip Nav Destination
Adolescent boy getting vaccinated

CDC panel supports longer interval between mRNA vaccine doses to reduce myocarditis risk

February 5, 2022

Editor’s note: For the latest news on COVID-19, visit

A federal panel of vaccine experts expressed support on Friday for lengthening the amount of time recommended between doses of mRNA COVID-19 vaccines to reduce the already small risk of myocarditis and improve efficacy. However, no final decision has been made.

The discussion followed an announcement of changes to vaccine intervals for adolescents and adults who are immunocompromised. The Centers for Disease Control and Prevention’s (CDC’s) Advisory Committee on Immunization Practices (ACIP) also recommended use of Moderna’s COVID-19 vaccine for all adults under full licensure.

Potential changes to vaccine intervals

Federal officials have continued to closely monitor cases of myocarditis after vaccination, which primarily have been seen in adolescent and young adult males after a second dose of mRNA vaccine.

The latest data from the Vaccine Safety Datalink, a network of nine health care organizations, found that among 18- to 39-year-old males and females, there are about 22 myocarditis/pericarditis cases per million second doses of Pfizer-BioNTech and 31 excess cases per million second doses of Moderna when compared to a similar group.

Health officials from Canada presented data to ACIP Friday showing that increasing the time between the first and second dose of these vaccines beyond the current three weeks for Pfizer-BioNTech and four weeks for Moderna can lower the risk of myocarditis. Data from Canada and England also show a longer interval was linked to increased vaccine effectiveness and antibody responses. The safety and effectiveness benefits appear to be greatest at about eight weeks.

ACIP members expressed support of an eight-week interval. ACIP member Helen Keipp Talbot, M.D., associate professor of medicine at Vanderbilt University, called it a “win-win.”

“It’s not only a reduction of adverse events, but it’s also the improvement in immunogenicity,” she said. “As we approach these new variants, the higher the antibodies and the more diverse the antibodies are, the better protected people will be.”

ACIP COVID-19 Vaccines Work Group Chair Matthew F. Daley, M.D., FAAP, senior investigator at the Institute for Health Research at Kaiser Permanente Colorado, said the proposed change also may help vaccination rates.

“If we’re communicating we have vaccines that are highly effective and have a high degree of safety but we have a way to make them even safer and reduce the risk for myocarditis, and if that’s the particular reason why they’re hesitant, it could encourage some additional vaccination,” he said.

Dr. Daley acknowledged there is a risk of people getting infected between doses but said the interval still would be relatively short and people would have some protection from the first dose. It could be especially beneficial if implemented when cases were falling.

Federal officials will continue to look at whether and how to go about changing the interval and what age groups would be impacted by the change.

Changes to vaccines for immunocompromised, passive antibody products

The CDC announced changes Friday to the vaccine recommendations for people ages 12 and older who are moderately or severely immunocompromised. Those who have received three doses of an mRNA vaccine can get a booster dose three months later instead of waiting five months.

The change was made due to concern about whether this group has mounted a sufficient immune response and whether they are losing protection over time. The CDC also will allow providers who care for people who are immunocompromised to administer mRNA vaccines outside recommended dosing intervals on a case-by-case basis when they determine the benefits outweigh potential risks.

The CDC also now recommends immunocompromised people who received a Johnson & Johnson (J&J) primary dose get a dose of an mRNA vaccine at least 28 days afterward and a booster two months after the second dose.

In another change, there no longer is a recommended deferral period between COVID-19 vaccination and passive antibody products used for post-exposure prophylaxis or treatment. However, tixagevimab/cilgavimab should be deferred for at least two weeks after vaccination.

Moderna COVID-19 vaccine licensure

In another move Friday, ACIP members voted 13-0 to approve using the Moderna COVID-19 vaccine known as Spikevax for adults under full licensure, and the CDC director agreed with the recommendation.

The vaccine has been used for a little over a year under emergency use authorization (EUA). It still will be used under EUA for adults’ boosters and immunocompromised adult’s third primary series dose. The vaccine is 93% effective at preventing COVID-19 and 98% effective at preventing severe disease. The most common side effects in clinical trials were pain/redness at the injection site, fatigue, headache, muscle or joint pain and chills. Officials said the benefits of protection against COVID-19 outweigh the small risk of myocarditis after vaccination.



Close Modal

or Create an Account

Close Modal
Close Modal