New report offers ‘most compelling’ evidence yet of COVID-19 vaccines’ effectiveness
Messenger RNA vaccines by Pfizer-BioNTech and Moderna were 94% effective at preventing symptomatic COVID-19 among health care workers after two doses and more than 80% effective after one, researchers reported in MMWR.
The study — and others like it — was “pivotal” to the CDC changing its recommendations for people who are fully vaccinated against COVID-19, said CDC Director Rochelle P. Walensky, MD, MPH.
“This report provided the most compelling information to date that COVID-19 vaccines were performing as expected in the real world,” Walensky said in a statement.
After relaxing outdoor mask guidance last month, the CDC said Thursday that fully vaccinated Americans no longer need to wear masks or socially distance indoors, returning the country to “some sense of normalcy” after more than a year, Walensky said.
In the new study, Tamara Pilishvili, PhD, MPH, an epidemiologist in the CDC’s National Center for Immunization and Respiratory Diseases, and colleagues conducted a test-negative design case-control study of COVID-19 vaccine effectiveness at 33 sites in 25 states from January to March. The study population included 623 case patients and 1,220 controls.
The calculated vaccine effectiveness following a single dose, measured 14 days after receiving the shot, was 82% (95% CI, 74%-87%). Effectiveness 7 days or more after the second dose was 94% (95% CI, 87%-97%).
On May 12, the CDC expanded its COVID-19 vaccine recommendations to include those aged 12 to 15 years for the Pfizer-BioNTech vaccine. Given the effectiveness of the vaccine, the CDC recommends anyone aged 12 years or older receive it.
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