CDC Study Finds Vaccine Effectiveness Against Mild or Moderate Infections ‘May Wane over Time’

A girl gets a Pfizer BioNTech COVID-19 vaccine in Bucharest, Romania, Wednesday, June 2, 2021. Romania has started the vaccination campaign for children between the ages of 12 and 15. (AP Photo/Andreea Alexandru)
AP Photo/Andreea Alexandru

A study from the Centers for Disease Control and Prevention (CDC) found that vaccine efficacy against mild or moderate cases of the Chinese coronavirus “may wane over time,” prompting federal health officials to recommend booster shots eight months after vaccination and embrace additional mitigation strategies, such as masking up yet again.

This particular study, released August 18, had the New York State Department of Health link “statewide immunization, laboratory testing, and hospitalization databases for New York to estimate rates of new laboratory-confirmed COVID-19 cases and hospitalizations by vaccination status among adults” and found that “current” vaccines were “highly effective against hospitalization (VE >90%) for fully vaccinated New York residents, even during a period during which prevalence of the Delta variant increased from <2% to >80% in the U.S. region that includes New York, societal public health restrictions eased, and adult full-vaccine coverage in New York neared 65%.”

However, the study also found case rates increasing among both unvaccinated and fully vaccinated adults.

“Moreover, VE against new infection declined from 91.7% to 79.8%. To reduce new COVID-19 cases and hospitalizations, these findings support the implementation of a layered approach centered on vaccination, as well as other prevention strategies,” the study found, ultimately concluding that the vaccines assist in preventing hospitalization, but vaccine efficacy has declined in New York, “coinciding with a period of easing societal public health restrictions and increasing Delta variant circulation”:

Researchers say the findings “support a multipronged approach to reducing new COVID-19 hospitalizations and cases, centered on vaccination, and including other approaches such as masking and physical distancing.”

On Wednesday, federal health officials affiliated with the Centers for Disease Control and Prevention (CDC), the Food and Drug Administration (FDA), the National Institutes of Health (NIH), National Institute of Allergy and Infectious Diseases (NIAID), and White House COVID-19 Response team released a joint statement recommending vaccine booster shots after eight months. They cited “evidence of reduced protection against mild and moderate disease” in those who have been vaccinated. As a result, booster shots, they said, are “needed to maximize vaccine-induced protection and prolong its durability.”


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