When the COVID-19 pandemic first began, the general thought was that once people were infected, they were then protected from the virus.
It’s hard to say how many. The ABC News analysis found at least 1.6 million reinfections in 24 states, but the actual number is probably a lot higher.
“These are not the real numbers because many people are not reporting cases,” Ali Mokdad, MD, an epidemiologist with the University of Washington, Seattle, told ABC.
The latest variant, BA.5, has become the dominant strain in the United States, making up more than 65% of all COVID-19 cases as of July 13, according to data from the CDC.
Prior infections and vaccines aren’t providing as much protection against the newly dominant BA.5 strain as they did against earlier variants.
But evidence doesn’t show this subvariant of Omicron to be more harmful than earlier, less transmissible versions.
Several factors are contributing to rising reinfections, experts say. For example, fewer people are wearing masks than in the first year or so of the pandemic. Dr. Mokdad said just 18% of Americans reported always wearing a mask in public at the end of May, down from 44% the year before.
The emergence of the Omicron variant, of which BA.5 is a subvariant, is indicating that less protection is being offered by prior infections.
A version of this article first appeared on WebMD.com.