An eight-week interval between first and second doses of COVID-19 mRNA vaccines may be optimal for some people 12 and older, according to CDC vaccination schedule guidance updated Feb. 22.
Some studies have indicated extending the time between first and second doses may reduce the small risk of myocarditis (heart muscle inflammation), particularly among young men, the CDC said. It may also boost peak antibody responses and vaccine effectiveness.
"Therefore, an eight-week interval may be optimal for some people ages 12 years and older, especially for males ages 12–39 years," the CDC said.
The original recommended interval between first and second doses was three weeks for Pfizer recipients and four weeks for Moderna recipients. These shorter intervals are still recommended for immunocompromised recipients, people 65 and older, and others who "need rapid protection due to increased concern about community transmission or risk of severe disease," the CDC said.