The Centers for Disease Control and Prevention updated its COVID-19 vaccine guidance on Tuesday to recommend that some Americans over the age of 12 who have received a first mRNA vaccine dose, wait up to eight weeks before getting their second dose, instead of the previously recommended three to four.
Several studies suggest that an extended interval between initial dosing may help improve vaccine effectiveness and decrease the small, but potential risk of myocarditis, a rare form of heart inflammation that occurs after vaccination, the agency wrote.
Although an increased risk of myocarditis, particularly among young men, has been identified with both the Pfizer and Moderna vaccines, extensive data analysis over the course of the pandemic has shown that COVID-19 mRNA vaccines are overwhelmingly safe, not only in clinical trials, but also in the real world. The risk of myocarditis is also higher if you get COVID-19 itself than with the vaccine.
“mRNA COVID-19 vaccines are safe and effective at the FDA-approved or FDA-authorized intervals, but a longer interval may be considered for some populations,” the agency wrote in its updated recommendations.
In particular, the CDC emphasized that young men, between the ages of 12–39 years, who may be at increased risk for myocarditis, should consider this extended time series.
“Extending the interval between the first and second mRNA vaccine dose to 8 weeks might reduce the risk [of myocarditis],” the agency wrote.
The original waiting period between the first and second dose is still recommended for immunocompromised Americans, adults over the age of 65, and those who may need more rapid protection, due to an increased risk of infection or severe disease.
Experts emphasize that at this time, there is no new safety risk associated with COVID-19 vaccines. This change in guidance is not directly relevant for the 215 million Americans who have already been fully vaccinated. Rather, it is a consideration for those who have yet to be fully vaccinated.
Experts say that Americans should talk to their doctor about potentially spacing out the dosing.
Booster doses continue to be recommended for most Americans, five months after completion of the primary mRNA series, or two months after a Johnson & Johnson single-dose vaccination.