(WJW/AP) — A new report from the Centers for Disease Control and Prevention says the delta variant of the coronavirus is as contagious as chickenpox, and as vaccinations in Americans increase, so will the number of vaccinated people contracting the disease.

It also notes that the infections in vaccinated people may be as transmissible as in the unvaccinated.

The report released Friday details an outbreak following multiple large public events in Barnstable County, Mass., in July 2021. According to the CDC, 469 COVID-19 cases were identified in residents who were there between July 3 and July 17.

Of those infected, 346 were fully vaccinated. About 274 of the 469 with breakthrough infection were symptomatic. Five patients were hospitalized, four of whom were vaccinated. No deaths were reported.

The delta variant was found in specimens of a majority of those tested.

The documents point out that the delta variant, first detected in India, causes infections that are more contagious than the common cold, flu, smallpox and Ebola virus, and is as infectious as highly contagious chickenpox.

Since January, people who got infected after vaccination make up an increasing portion of hospitalizations and in-hospital deaths among COVID-19 patients, according to the documents. That trend coincides with the spread of the delta variant.

The report emphasizes that vaccination is still the most important strategy to prevent severe illness and death.

The report included information that prompted U.S health officials to consider changing advice on how the nation fights the coronavirus. Last week, the CDC recommended that people in areas with high transmission wear masks in indoor public settings regardless of their vaccination status.

Recommending masks for everyone and requiring vaccines for doctors and other health workers are among measures the Centers for Disease Control and Prevention is considering.