As the coronavirus continues to evolve, Omicron subvariants such as BA.4 and BA.5 are expected to lead to many COVID-19 cases in the coming months.
Researchers recently reported that the subvariants have mutated for better “immune escape,” or the ability to avoid antibodies from vaccination or previous infection.
“That has changed our view for what will happen this summer,” Ali Mokdad, PhD, an epidemiologist who has developed COVID-19 forecasts for the University of Washington’s Institute for Health Metrics and Evaluation in Seattle, told The Boston Globe.
Until recently, Dr. Mokdad expected the United States to have a “very good summer” in terms of cases, hospitalizations, and deaths through September. The U.S. is reporting about 100,000 new cases per day, according to the data tracker by The New York Times, which has remained flat throughout June. Cases will likely decrease this summer, Dr. Mokdad said, though the decline will be slower and smaller than first thought.
As of June 18, BA.4 and BA.5 accounted for about 35% of cases in the United States, according to the latest CDC data, with BA.5 making up 23.5% and BA.4 making up 11.4%. The two subvariants will likely take over BA.2.12.1 as top subvariants in coming weeks.
“I expect that BA.5 will likely become the dominant virus in the United States this summer,” Dan Barouch, MD, director of the Center for Virology and Vaccine Research at Beth Israel Deaconess Medical Center in Boston, told the Globe.
Dr. Barouch said the Omicron subvariants will likely create a summer of “substantial infections” but low rates of hospitalization and death. He published a recent study in the New England Journal of Medicine that found BA.4 and BA.5 are better at escaping antibodies than other coronavirus strains – about three times better than the Omicron variants BA.1 and BA.2 and 20 times better than the first coronavirus strain.
“What we’re seeing with each subsequent variant is iteratively higher levels of transmissibility and higher levels of antibody immune escape,” he said. “We’re seeing high levels of infection in populations that are highly vaccinated, as well as populations that have a high level of natural immunity to the prior variants.”
At the same time, current antibodies still appear to protect people against the worst outcomes, Dr. Barouch said.
“If people have vaccine immunity or natural immunity, then they have substantial protection against severe disease,” he said.
So far, researchers have found that Omicron subvariants tend to cause less severe disease than other variants, such as Delta. Dr. Mokdad estimated that 80% of Omicron infections don’t show symptoms.
He said there is a “remote possibility” of another wave during the summer, but he expects cases to rise significantly around the beginning of October, when the seasons change, and most people’s immunity will wane. Other things could play into the predictions this summer, he noted, such as coronavirus mutations and new variants.
“Anybody that models this more than a couple of weeks out is basically just using pixie dust,” Michael Osterholm, PhD, director of the Center for Infectious Disease Research and Policy at the University of Minnesota, Minneapolis, told the newspaper.
“There is no pattern whatsoever developing from a seasonality standpoint. It’s all being driven by the variants,” he said. “We just have to be humble and acknowledge that we don’t know.”
A version of this article first appeared on WebMD.com.