CDC to consider increasing time between vaccine doses to lower risk of heart inflammation

The Centers for Disease Control and Prevention are considering changing vaccine guidance to lengthen the time in between doses of certain vaccines because of the risk of heart inflammation.

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More time between the first two doses of the mRNA COVID-19 vaccines appears to reduce the risk of myocarditis, a rare type of heart inflammation seen in some after getting an mRNA vaccine, and it could improve the shots’ effectiveness, researchers told the CDC’s Advisory Committee on Immunization Practices.

According to the CDC, the proposed changes would apply to the Pfizer and Moderna COVID-19 vaccines, which use the mRNA technology.

Under the current guidelines, the two Pfizer COVID-19 vaccine doses are given three weeks apart, and the two COVID-19 vaccine doses from Moderna are given four weeks apart.

Reports of an increase in myocarditis in some – particularly men between the ages of 18 and 39 – following a COVID-19 vaccination prompted researchers to look at the interval between doses, Dr. Nicola Klein, a vaccine researcher at Kaiser Permanente Northern California, told the committee in a presentation Friday.

According to Dr. Bryna Warshawsky, a medical adviser with the Public Health Agency of Canada, rates of myocarditis fell when the interval between the two doses was extended.

In addition to a decline in the rate of myocarditis, researchers reported to the committee that a greater interval between doses appears to create higher antibody responses from the body and higher vaccine effectiveness.