The Centers for Disease Control and Prevention has said that males ages 12 to 39 can extend the time between the first and second doses of an mRNA COVID-19 vaccine to mitigate the relatively low risk of developing myocarditis.

The agency announced on Tuesday that male patients could receive the second shot eight weeks after the first, instead of waiting, as previously advised, three weeks in the case of the Pfizer-BioNTech vaccine or four weeks in the case of the Moderna vaccine. The CDC urged men to take caution about myocarditis, the rare cardiac episode which causes inflammation of the heart muscle that can reduce the heart’s ability to pump and cause arrhythmias. While the risk exists, the top public health agency insists the condition is rare.