Researchers Advise CDC To Increase Intervals Between Vaccine Doses, Citing Heart Inflammation Concerns

The Centers for Disease Control and Prevention (CDC) are considering changing vaccine guidance to lengthen the time in between doses of COVID vaccines in order to cut down on risk of heart inflammation. More time between the first two doses of the mRNA COVID-19 vaccines appears to reduce the risk of myocarditis, a form of heart inflammation seen in some after getting an mRNA vaccine, researchers told the CDC’s Advisory Committee on Immunization Practices.

The proposed changes would apply to the Pfizer and Moderna COVID-19 vaccines, both of which use mRNA technology. Under the current guidelines, the two Pfizer COVID-19 vaccine doses are given three weeks apart, while the two COVID-19 vaccine doses from Moderna are administered four weeks apart. An increase in reports of myocarditis — particularly among between the ages of 18 and 39 – following a COVID-19 vaccination prompted researchers to look at the interval between doses. The information was presented to the committee by Dr. Nicola Klein, a vaccine researcher at Kaiser Permanente Northern California,  in a presentation on 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. Researchers also said that increasing the intervals between doses produced “higher antibody responses from the body and higher vaccine effectiveness.”

Dr. Grace Lee, a medical officer at the Lucile Packard Children’s Hospital and the advisory panel’s chair, said the data presented was “fairly convincing that an extended interval is not only potentially safer from a myocarditis standpoint, but also potentially more effective.”

Current CDC guidance calls for immunocompromised individuals to receive three doses of an mRNA vaccine within two months, and a fourth dose at least five months after the third dose. U.S. health officials currently recommend the shots for all Americans over the age of four, asserting the vaccines prevent more hospitalizations than the heart inflammation cases they cause.

The CDC hasn’t yet decided whether to follow the panel’s advice.


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