LOS ANGELES, United States — The BA.5 Omicron subvariant, now the dominant coronavirus strain in the United States, is four times more resistant to Covid-19 vaccines, according to a new study published in Nature.

The study found the variant is four times more resistant to messenger RNA vaccines than earlier strains of Omicron, which include Pfizer and Moderna Covid-19 vaccines.

The strain is “hypercontagious” and is contributing to increases in hospitalizations and ICU admissions, said the Mayo Clinic in a report on Thursday.

The BA.5 strain represented 65 percent of Covid-19 cases in the country in the week ending July 9, according to the latest data from the U.S. Centers of Disease Control and Prevention.

Unvaccinated people have about a five times higher chance of contracting the virus than those who are vaccinated and boosted, while chances of hospitalization are 7.5 times higher, and chances of death are 14 to 15 times higher, said Dr. Gregory Poland, head of the Mayo Clinic’s Vaccine Research Group.