New CDC studies show some fading of vaccine effectiveness against hospitalization in elderly

New CDC studies show waning vaccine effectiveness against hospitalization in elderly Two of the analyses suggest that as the Delta variant spread this summer, the shots became less effective at keeping people 75 and older out of the hospital. Erin Banco POLITICO

Covid-19 vaccines continue to work well at preventing severe disease for the vast majority of Americans but they are becoming less effective at blocking infection, according to a series of studies the Centers for Disease Control and Prevention released Friday.

Two of the analyses suggest that as the Delta variant spread this summer, the shots became less effective at keeping people 75 and older out of the hospital. ...

CDC began last month to release the results of targeted vaccine effectiveness studies, showing protection against infection beginning to wane in residents of New York and Los Angeles and among frontline health care workers. But the agency has taken weeks to complete one of its largest and most comprehensive analyses of breakthrough infections — based on data from 13 jurisdictions with the ability to match immunization records with Covid-19 lab reports.

That study, one of the three released Friday, compared the relative risks of infection, hospitalization and death between people who are fully vaccinated and those who are not across different age groups. The CDC looked at 600,000 people infected with Covid-19 from April through mid-July. It found that overall, vaccine effectiveness against severe Covid-19 disease remains high. Incidence rate ratios for hospitalization and death changed relatively little after the Delta variant became the most dominant strain of the virus in the U.S., the study showed.

But the vaccines’ ability to prevent any infection — including mild disease — decreased from 91 percent to 78 percent after the Delta variant took over this summer. ...