Fully vaccinated breakthrough COVID-19 cases are increasing amid delta variant;
The latest CDC studies showed the Pfizer-BioNTech and Moderna mRNA vaccines may not be as effective against the delta variant compared with the original virus.
- In one study, researchers found the effectiveness of the vaccines against infections declined from 91.7% to 79.8% between May 3 and July 25 as the delta variant dominated cases in New York.
- Another study published by the agency found the two mRNA vaccines were 74.7% effective in nursing home residents nationwide between March and May, but protection droppedto 53.1% between June and July, alsoas the delta variant picked up momentum.
- While it is clear breakthrough infections are increasing, the studies showed hospitalizations remained stable, an indication the vaccines continue to hold up against severe illness.