Substrains of the Omicron BA.4 and BA.5 appear to avoid antibody responses in both people previously infected with COVID-19 and those who have been fully vaccinated, the new data from researchers at Beth Israel Deaconess Medical Center and Harvard Medical School reported.
Neutralizing antibody levels caused by previous infection or vaccination are several times lower for BA.4 and BA.5 subvariants compared with the original coronavirus, according to the new study, published in the New England Journal of Medicine.
"We observed 3-fold reductions of neutralizing antibody titers induced by vaccination and infection against BA4 and BA5 compared with BA1 and BA2, which are already substantially lower than the original COVID-19 variants," Dr. Dan Barouch, an author of the paper and director of the Center for Virology and Vaccine Research at Beth Israel Deaconess Medical Center in Boston, wrote in an email to CNN.
"Our data suggest that these new Omicron subvariants will likely be able to lead to surges of infections in populations with high levels of vaccine immunity as well as natural BA1 and BA2 immunity," Barouch wrote. "However, it is likely that vaccine immunity will still provide substantial protection against severe disease with BA4 and BA5."
The recently published results echo a separate study by scientists at Columbia University.
The authors of that study note that their results indicate a higher risk of reinfection even in people with some prior immunity to the coronavirus.
BA.4 and BA.5 caused about 35 percent of new COVID-19 infections in the United States last week, up from 29 percent the week before, according to the U.S. Centers for Disease Control and Prevention Tuesday.
BA.4 and BA.5 are the fastest spreading variants reported to date and are expected to dominate COVID-19 transmission in the United States, the United Kingdom and the rest of Europe over the next few weeks.