The interval between the first and second doses of the Pfizer and Moderna COVID-19 vaccines can be up to eight weeks for some people, stated the US Centers for Disease Control and Prevention in its updated vaccine guidance.

According to the previous guidance, the second doses had to be administered three weeks following the first dose of the Pfizer vaccine or four weeks after the first jab of the Moderna vaccine.

The agency said that the vaccines remain safe and effective at the original intervals. However, increasing the interval may reduce the risk of myocarditis in some populations. Rare cases of myocarditis have been reported, largely after the second dose of mRNA vaccines, with males aged 12 to 29 years being at highest risk. The CDC said that the relative risk for myocarditis appears to be higher for males aged 12-39 years, and might be reduced by increasing the interval between the first and second shots.

The agency stated that the three- or four-week interval continues to be recommended for moderately or severely immunocompromised individuals, adults aged 65 years and older, and people who need quick protection on account of increased concern of community transmission or risk of severe disease… (CNN, February 24, 2022)