Fully vaccinated frontline healthcare workers were significantly better protected from contracting COVID-19 before the delta variant emerged as the dominant strain, according to new data released by the Centers for Disease Control and Prevention.
CDC researchers said the trend should spark caution in providers since it shows a clear decline in vaccine effectiveness, even as increases in COVID-19 breakthrough cases are being reported..
“Active surveillance through the cohort is ongoing and [vaccine effectiveness] estimates will be monitored continuously,” the authors concluded. “Although these interim findings suggest a moderate reduction in the effectiveness of COVID-19 vaccines in preventing infection, the sustained two thirds reduction in infection risk underscores the continued importance and benefits of COVID-19 vaccination.”
Findings published Tuesday in the CDC’s Morbidity and Mortality Weekly Report found full COVID vaccination was 80% effective in preventing infection among frontline workers between December and mid-August. From December to April, just before the arrival of the delta variant, vaccine effectiveness among the group was even better, at 91%, according to the CDC’s COVID Response Team.
The study was conducted over 35 weeks and had a total of 4,217 participants — with 83% of them being vaccinated. A total of 488 unvaccinated participants contributed an average of 43 days to their providers and had 19 COVID-19 infections since April, during the delta-variant predominant weeks of the investigation.
The 2,353 fully vaccinated employees worked an average of 49 days and had 24 infections among them during the same time period.
