Rochelle Walensky, the director of the U.S. Centers for Disease Control and Prevention, said Wednesday that coronavirus vaccines have been found to be less effective against the delta variant and have “waning” effectiveness over time, but are still preventing hospitalizations and death – the basis for the administration’s new plan to provide booster shots.
Citing three studies published in CDC’s latest Morbidity and Mortality Weekly Report, Walensky said at a White House briefing that vaccine effectiveness has been found to fall over time.
A National Healthcare Safety Network study found vaccines’ effectiveness in preventing infection for nursing home residents – among those most vulnerable to the virus – fell from 75% to 53% between March and July, Walensky said, as the delta variant became more widespread
Walensky also cited a Mayo Clinic study that has yet to be peer reviewed found that effectiveness of the Pfizer-BioNTech vaccine fell from 76% in January to 42% in July, while the effectiveness of the Moderna vaccine declined from 86% to 76% over the same span.
Walensky also cited an Arizona HEROES/RECOVER study that shows vaccines that are 92% effective against the original strain of the virus are just 64% effective against delta.
However, according to Walensky, the Mayo Clinic study and a New York State study that also found vaccine effectiveness decreases over time both concluded that their effectiveness against severe infection and death remains high and stable.
200 million. That’s how many Americans have gotten at least one vaccine shot, White House coronavirus response coordinator Jeff Zients said at the briefing, with 7 million newly vaccinated Americans in the last two weeks, the highest rate since June.
What To Watch For
The Biden administration plans to recommend those fully vaccinated for coronavirus get a third booster shot 8 months after their second shot. Zients said the shots will be free and as widely available as the first two shots.