Newly updated Centers for Disease Control and Prevention guidance says some people should wait eight weeks between first and second doses of the Pfizer-BioNTech and Moderna coronavirus vaccines, rather than the three- to four-week intervals initially recommended.
The change was made Tuesday on the CDC’s website. It says an eight-week interval “may be optimal for some people ages 12 years and older, especially for males ages 12 to 39 years.” The CDC cited the small risk of a rare heart condition in that population and said the risk might be reduced by extending the length of time between doses.
It added that some studies in adolescents and adults have also suggested peak antibody response and vaccine effectiveness may increase with the longer spacing between shots.
As vaccines became available last year, British health officials stretched the interval between doses as part of an effort to get vaccines to as many people as possible. A study published last summer found that the longer gap led to higher overall antibody levels.
The shorter interval — three weeks for the Pfizer-BioNTech vaccine and four weeks for the Moderna vaccine — is still recommended by the CDC for people 65 and older, those who are immunocompromised and others who need rapid protection because of concern over high community spread or risk of severe disease.
Federal health officials have said there is probably a link between two coronavirus vaccines and increased risk of a rare condition, myocarditis, predominantly in men between the ages of 12 and 39. Most cases have been mild, and medical authorities have said the benefits of the shots outweigh the risks.
Among men ages 18 to 39, the condition has been reported in about 68 per 1 million getting the second Moderna dose and about 47 per 1 million getting the second Pfizer dose, the Associated Press reported.
William Schaffner, a Vanderbilt University vaccines expert, told the AP that the CDC’s action was sensible, saying that earlier in the pandemic, with the virus spreading and people dying, “we wanted to get the vaccine into their arms as quickly as possible.”
If those who are already vaccinated worry the original schedule has given them less than the maximum amount of protection, they can seek out a booster shot, he said.
“We really have very good data indicating that two doses plus the booster provide very strong protection against severe disease,” Schaffner said.
