BA.4 and BA.5 can substantially escape neutralizing antibody responses from both vaccination and prior infection, according to research from a team at Beth Israel Deaconess Medical Center in Boston.
The CDC estimates the COVID-19 strains — known as "sister variants" — now account for nearly 35 percent of U.S. cases.
Researchers evaluated antibody responses to numerous omicron subvariants among 27 people who had been vaccinated and boosted, as well as 27 people with a prior infection.
The findings, published June 22 in the New England Journal of Medicine, showed antibody responses against BA.4 and BA.5 were twentyfold lower than to the original omicron strain and threefold lower against subvariants BA.1 and BA.2.
"We observed a threefold reductions of neutralizing antibody titers induced by vaccination and infection against BA.4 and BA.5 compared with BA.1 and BA.2, which are already substantially lower than the original COVID-19 variants," Dan Barouch, MD, PhD, study author and director of the Center for Virology and Vaccine Research at Beth Israel Deaconess Medical Center, told CNN.
Dr. Barouch added the data indicate the new strains will lead to surges among vaccinated populations, as well as populations with high levels of immunity against BA.1 and BA.2 from prior infections. "However, it is likely that vaccine immunity will still provide substantial protection against severe disease with BA.4 and BA.5," he told CNN.