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The Centers for Disease Control and Prevention (CDC) has updated its guidance to lengthen the interval between initial doses of mRNA COVID-19 vaccines to reduce the already small risk of myocarditis and improve efficacy.
The interval between first and second doses of the Pfizer-BioNTech and Moderna COVID-19 vaccines may be as long as eight weeks for certain people, the CDC announced Tuesday. The new guidance is intended to help health care providers recommend the optimal COVID-19 vaccination schedule based on the individual patient.
People ages 12-64 years, who are not moderately or severely immunocompromised — and particularly males ages 12-39 years — may benefit from getting their second mRNA COVID-19 vaccine dose 8 weeks after their first dose instead of the 3-week (Pfizer-BioNTech) or 4-week (Moderna) interval, recommended under previous CDC Guidance.
Patients who meet these criteria and already have received their primary mRNA series at the previous intervals remain well-protected, especially if they have received a booster dose, according to the CDC. They do not need to repeat any doses.
According to the guidance, the longer interval between vaccine doses gives the body more time to build a stronger immune response and further minimize the already rare risk of adverse events, such as myocarditis, which is rare and seen primarily in males ages 18-39 years.
The extended interval is not recommended for all people ages 12-64 years. Providers should continue to recommend the three-week (Pfizer-BioNTech) or four-week (Moderna) intervals between primary doses in situations, such as: where high levels of community transmission exist; among those who are moderately or severely immunocompromised, and; anyone age 65 years or older.
Federal officials have been closely monitoring cases of myocarditis after vaccination, which primarily have been seen in adolescent and young adult males after a second dose of mRNA vaccine.
Earlier this month, health officials from Canada presented data to the CDC’s Advisory Committee on Immunization Practices (ACIP), which showed that increasing the time beyond the 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.
Regardless of the interval between the first and second dose, data show mRNA vaccines remain highly effective at reducing the risk of hospitalization or serious complications from COVID-19 infection, the CDC guidance said.
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