Interval between COVID-19 vaccine doses can be 8 weeks for some people, CDC says
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The interval between the first and second doses of the Pfizer-BioNTech and Moderna COVID-19 vaccines can be 8 weeks for certain people, the CDC said in updated interim guidance.
Previous guidance stated that first and second doses should be separated by 3 weeks for the Pfizer-BioNTech vaccine and 4 weeks for the Moderna vaccine.
The CDC said both vaccines remain safe and effective when given at those intervals, but the longer interval could reduce the risk for myocarditis, which is rare after receiving a messenger RNA-based COVID-19 vaccine but elevated among male adolescents and young adults, studies have shown.
“While absolute risk remains small, the relative risk for myocarditis is higher for males ages 12-39 years, and this risk might be reduced by extending the interval between the first and second dose,” the CDC wrote in the updated guidance.
It noted that research has shown that the small risk “might be reduced and peak antibody responses and vaccine effectiveness may be increased with an interval longer than 4 weeks."
"Extending the interval beyond 8 weeks has not been shown to provide additional benefit,” the CDC wrote. “There are currently no data available for children ages 11 years and younger. Therefore, an 8-week interval may be optimal for some people ages 12 years and older, especially for males ages 12-39 years.”
The CDC said the 3- or 4-week interval is still recommended for people who are moderately or severely immunocompromised, adults aged 65 years or older and other people “who need rapid protection due to increased concern about community transmission or risk of severe disease."
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The CDC has updated the recommendations for the interval between the first and second dose of mRNA vaccines for young men by extending it to 8 weeks. This was done based on data presented at the Advisory Committee on Immunization Practices meeting on Feb. 4, where data on myocarditis after vaccination was presented, as well as evidence that the risk for myocarditis for young men decreases significantly if the vaccine doses are spaced out to 8 weeks. The data also suggest that the risk for myocarditis is much lower with the Pfizer-BioNTech than with the Moderna mRNA vaccine, and thus the former is the preferred vaccine for young men. These recommendations are similar to the ones made by Canadian health authorities.
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CDC. Interim clinical considerations for use of COVID-19 vaccines currently approved or authorized in the United States.https://www.cdc.gov/vaccines/covid-19/clinical-considerations/covid-19-vaccines-us.html. Accessed on Feb. 23, 2022.
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