The U.S. Centers for Disease Control and Prevention released a new report Friday that showed a high number of infections among fully vaccinated people associated with multiple summer events in Barnstable County, Massachusetts.
According to the CDC, 469 people in that area tested positive for COVID-19 this month. Roughly three quarters (346; 74%) of them had been fully vaccinated.
A person is considered fully vaccinated two weeks after receiving the second dose of a Pfizer or Moderna shot or a single dose of the Johnson & Johnson jab. A breakthrough case occurs when a fully vaccinated person becomes infected.
In this photo illustration, vials of fake 'Covid-19 Vaccine' and a syringe seen displayed with a logo of Centers for Disease Control and Prevention (CDC) in the background. (Photo Illustration by Pavlo Gonchar/SOPA Images/LightRocket via Getty Images
In all, 79% (274) of those breakthrough cases experienced COVID symptoms. Of the five total hospitalizations, four of them had been vaccinated.
Health officials have stressed the importance of vaccination for months, saying mutations like the Delta variant could prove more transmissible than previous strains. Vaccination coverage among eligible Massachusetts residents was 69%.
The CDC conducted genomic sequencing on 133 Massachusetts residents and found the Delta variant in 119 of them and the Delta AY.3 sublineage in one.
Even so, the CDC cautions the public from drawing the wrong conclusion based on these findings — calling the data insufficient.
They said vaccinated people are likely to represent a larger proportion of COVID-19 cases as population-level vaccination coverage increases.
They also said asymptomatic breakthrough infections might be underrepresented in the data because of a detection bias.
This story was reported from Atlanta.