Antibody response to vaccines among hospitalized veterans dips after 4 months, CDC study finds

The antibody response to Pfizer-BioNTech's and Moderna's mRNA COVID-19 vaccines fell after 120 days days among hospitalized veterans, suggesting the importance of booster doses for lasting protection, according to the CDC's Dec. 10 Morbidity and Mortality Weekly Report

Researchers evaluated the vaccine effectiveness among 1,896 U.S. veterans at five Veterans Affairs medical centers from Feb. 1 to Sept. 30. They measured antibody levels once between 14-119 days after the second dose and again at least 120 days after. 

Among both Moderna and Pfizer recipients, antibody responses decreased over time, though Moderna recipients maintained higher levels of antibodies than those who got Pfizer's shot, the findings showed. 

Between 14 and 119 days after the second dose, researchers found Moderna's vaccine effectiveness to be 89.6 percent, which fell to 86.1 percent at least four months after receiving the second dose. For Pfizer recipients, vaccine effectiveness was measured at 86 percent and 75 percent, respectively. 

The vaccines remained effective at preventing COVID-19-associated hospitalizations, despite the waning immunity, researchers said. 

"These findings from a cohort of older, hospitalized veterans with high prevalences of underlying conditions suggest the importance of booster doses to help maintain long-term protection against severe COVID-19," the report said.

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