The BA.4 and BA.5 sub-variants of omicron are estimated to make up about 8.3 percent and 13.3 percent of the coronavirus variants in the United States as of June 11, the US Centers for Disease Control and Prevention (CDC) said on Tuesday.
The two fast-spreading sublineages were added to the World Health Organization’s monitoring list in March and have also been designated as variants of concern in Europe.
The European Union’s disease prevention agency said on Monday the new subvariants are spreading more quickly than other variants, which could lead to more hospitalizations and deaths as they become dominant in the continent.
“I’m very concerned,” said Dr. Gregory Poland, head of Mayo Clinic’s vaccine research group in Rochester, Minnesota, adding that data from South Africa shows the subvariants are better at circumventing immunity provided through vaccines and previous infections.
Vaccines or previous infection may provide benefit right now, but BA.4 and BA.5 could potentially cause death and severe illness during summers when kids go back to school and people’s second booster may well have worn off, he said.
BA.4 made up 5.4 percent of the variants in the United States for the week of June 5, according to CDC estimates, while BA.5 made up 7.7 percent of the variants.
The seven-day moving average of US COVID-19 cases stood at 105,615 as of June 11, up 6.7 percent from a week earlier.