Vaccine efficacy against hospitalization dips for adults over 65, NY health department study says

CHICAGO -- A new study from the New York's health department found that for most adults, all three COVID-19 vaccines continue to offer protection against hospitalization from the virus.

The exception was adults over 65 vaccinated with Pfizer and Moderna, who saw a very modest dip in efficacy against hospitalization. Among those 65 and older, Pfizer vaccine efficacy against hospitalization declined from 95 percent in May to 89.2 percent in August. Moderna vaccine efficacy against hospitalization for that same age group declined from 97.2 percent in May to 94.1 percent in August.

Boosters for those 65 and older and other specific groups are authorized for Pfizer's vaccine. The FDA and CDC are slated to weigh in on boosters for the Moderna and Johnson & Johnson vaccines by late October.

While vaccines are holding strong against hospitalizations, all three vaccines lost some ability to protect against breakthrough infections across all age groups, the study said. People vaccinated with Pfizer saw the sharpest decline, though Moderna and Johnson & Johnson also saw declines.

Some studies have suggested that as more time passes, vaccines will continue to lose their power to prevent infections along a gradual slope.

However, this new study suggested that the decline observed so far could have less to do with time passing and more to do with the emergence of new COVID-19 variants and changes in behavior, such as reduced mask wearing. For example, after the Delta variant became the overwhelmingly predominant variant, accounting for more than 85 percent of cases in New York, the declines seen in efficacy against infections plateaued.

This study reinforced a growing body of evidence suggesting that although breakthrough infections are becoming more common, people who are vaccinated generally speaking are not being hospitalized.

The study is not yet been peer reviewed.