The new P.1 variant of COVID-19 first found in travelers from Brazil has been detected in Massachusetts more than anywhere else in the country, and the lion’s share of those cases are part of a cluster on Cape Cod, according to researchers.New data from the Broad Institute of MIT and Harvard showed 54 cases of the P.1 variant were reported in Massachusetts — mostly on Cape Cod — during the month following the first reported case of the variant in the state in late February.“When you see that there are a lot of [P.1] cases in Massachusetts, that’s partially because we’re looking for it,” said William Hanage, an associate professor of epidemiology at the Harvard T. H. Chan School of Public Health. “It’s been expected to happen at some point and it’s certainly happened now.”The research suggests that 43of these cases form a single cluster that is likely linked to an introduction from Brazil, with the remaining cases of P.1 possibly stemming from Nebraska, Italy, and other areas, he said.“The majority of [the 54 total cases] are associated with a single cluster because as we know … the majority of cases do not transmit,” Hanage said. “The ones that do transmit, however, make up for it.”P.1 cases haven’t continued to climb in the state, but Hanage expects more to emerge.Research shows the variant spreads faster than the original COVID-19 strain, but scientists have yet to learn if it is more deadly or more likely to reinfect those who have already recovered from the virus.The variant’s introduction is a new source of concern on Cape Cod.About half of all municipalities in Barnstable County are at high risk for transmission, according to the state’s weekly COVID-19 public health report. Most have also seen an increase in cases and positivity rates over the last few weeks, a sign that a new surge could hit the area if these numbers continue to grow.At the same time, more residents on the Cape have been vaccinated than in any other region in Massachusetts.The state’s weekly vaccination report shows 44 percent of Barnstable County residents had received at least one does of a vaccine as of March 30 — the highest percentage in the state. The county also had 27 percent of its population fully vaccinated at that point, coming in second only to Martha’s Vineyard.Hanage said the variant cases on Cape Cod were detected when fewer people in the state had been vaccinated. While vaccines are likely effective against this new strain, he said Massachusetts still has a long way to go before it can ward off the virus’s variants.“To completely exclude this virus, we need to vaccinate a lot more people than we have already,” Hanage said. “The high vaccination rates [right now] are not themselves sufficient to be protective, and if we allow more transmission, then we’re going to get more cases.”Caroline Enos can be reached at [email protected] Follow her on Twitter @CarolineEnos.