The BA.4 and BA.5 sub-variants of Omicron are estimated to make up about 8.3% and 13.3% of the coronavirus variants in the United States as of June 11, the U.S. 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 a benefit against death or severe illness, but BA.4 and BA.5 could potentially cause a surge in infections during the summer, just as kids go back to school and people’s second booster may have worn off, he said.
BA.4 made up 5.4% of the variants in the United States for the week of June 5, according to CDC estimates, while BA.5 made up 7.7% of the variants.
The seven-day moving average of U.S. COVID-19 cases stood at 105,615 as of June 11, up 6.7% from a week earlier. (Reporting by Mrinalika Roy in Bengaluru and Julie Steenhuysen in Chicago; Editing by Arun Koyyur)