mRNA vaccine booster protection declines within months, report shows

Protection provided by booster shots of the mRNA vaccines from Moderna Inc and Pfizer starts waning quickly, according to data published in Friday’s Morbidity and Mortality Weekly Report from the U.S. Centers for Disease Control and Prevention (CDC).

Researchers reported that within two months after the second dose of an mRNA vaccine during the surge in infections caused by the Delta variant of the virus, vaccine efficacy was 94% against hospitalization and 92% against emergency department or urgent care (ED/UC) visits.

Efficacy waned thereafter, but climbed to 96% and 97%, respectively, at two months after a booster shot. Four months later, however, that protection had declined to 76% and 89%. Once Omicron became predominant, vaccine efficacy was 71% against hospitalization and 69% against ED/UC visits within two months after the second dose, 91% and 87% at two months after a booster, and 78% and 66% four months later.

The estimates are drawn from analyses of 241,204 COVID-related ED/UC visits and 93,408 hospitalizations between August and January.

“Our findings suggest that additional doses (of vaccines) may be necessary,” Brian Dixon of the Regenstrief Institute and Indiana University said in a statement. “We also found that people who are Hispanic or Black are half as likely to have a third vaccine dose than people who are white, making (them) more vulnerable to severe COVID.”