The Delta variant of COVID-19 has been found in samples taken from people sickened in a Provincetown outbreak that infected more than 250, including some who were already vaccinated, officials said Friday.
Cases began ticking upward in Provincetown around the July Fourth holiday and had grown by Wednesday to 256, including 190 Massachusetts residents, 109 of whom live in Barnstable County, Town Manager Alex Morse said.
The Delta variant is more transmissible than the original COVID-19 virus, the Department of Health said in a statement. Those infected with the Delta variant often have more of the virus in their respiratory tract compared to other variants, and could carry the virus for longer, the statement said.
The State Public Health Laboratory and the Broad Institute of MIT and Harvard contributed to genetic sequencing tests of virus samples that detected the Delta variant in the Provincetown cluster, the DPH said.
The department said that although there are vaccinated people within the Provincetown cluster, the total number of cases among vaccinated people remains extremely low across the state.
Only .1 percent, or 5,166 cases, have come from the more than 4.3 million fully vaccinated residents in Massachusetts, the statement said.
The Centers for Disease Control and Prevention estimates the Delta variant could be responsible for 83 percent of positive cases found between July 4 and 17 nationally, the DPH said.
The DPH maintains that the best protection against COVID-19 is to get vaccinated. People can visit vaxfinder.mass.gov for a list of vaccination locations.
Katie Redefer can be reached at email@example.com.