The US Centers for Disease Control and Prevention (CDC) has updated its guidance on how long people can wait between their first and second COVID-19 vaccine dose.
With mRNA shots, the CDC says older children and adults can wait up to eight weeks to receive their second shot. This includes both Pfizer and Moderna vaccines.
However, the wait time is shorter for children between five and eleven years old. They should get their second dose after three weeks of having received the first dose.
The health agency states that the eight-week interval “may be optimal for some people ages 12 years and older, especially for males ages 12 to 39 years.”
It says extending the interval between the two shots may reduce the risk of myocarditis, which is a type of heart inflammation.
Males between 12 and 39 years old are highest risk for myocarditis. Cases of myocarditis have been reported after the second dose, but are considered rare.
The CDC goes on to say that extending beyond the eight-week window shows no additional benefit.
Previous guidance said the second dose should be administered three weeks after the first shot of the Pfizer vaccine, or four weeks after the first shot of the Moderna vaccine.
People who are moderately or severely immunocompromised, or are 65 years or older, should stick with the shorter interval, the CDC advises.