BA.2 more contagious, but vaccinated less likely to spread it, study

The omicron BA.2 subvariant is inherently more contagious and better at evading vaccines than any other Covid strain, but vaccinated people don’t transmit it as easily as the unvaccinated, according to a Danish study published Sunday.

The new subvariant, which has rapidly become dominant in Denmark, spread more easily across all groups regardless of sex, age, household size and vaccination status, the study found. The probability that the subvariant would spread within a household was 39% for BA.2 compared with 29% for BA.1, the original omicron subvariant that was dominant across the world as of Jan. 19, according to the World Health Organization.

The study, led by a team of scientists affiliated with the University of Copenhagen and the Danish Health Ministry among other institutions, has not yet been submitted for peer review. Researchers have been publishing their findings before they are examined by other experts in the field due to the urgent nature of the pandemic.

BA.2 is more contagious than the original BA.1 subvariant among both vaccinated and unvaccinated people, but the relative increase in susceptibility to infection was significantly greater in vaccinated individuals than unvaccinated individuals. That indicates it’s even better at escaping vaccine protection than BA.1, which was already significantly more contagious than any other Covid variant, according to the study.

Transmission rates among unvaccinated people were higher with BA.2 compared with BA.1, indicating unvaccinated people were carrying a higher viral load with BA.2. Although fully vaccinated people are more likely to catch BA.2 than the previous strain, they are less likely to spread it to others, researchers found.

People who received a booster were even less likely to transmit the virus than people who were fully vaccinated.

“This indicates that after a breakthrough infection, vaccination protects against further transmission, and more so for BA.2 than BA.1,” the scientists found.

The study also noted that the higher susceptibility to infection and greater transmissibility of BA.2 will likely result in more extensive spread of the virus among unvaccinated kids in schools and daycare.

It is reassuring that BA.2 is generally milder compared with the delta variant, the scientists said, and the vaccines protect against hospital admissions and severe illness.

“The combination of high incidence of a relative innocuous subvariant has raised optimism,” the scientists wrote, while noting the importance of keeping a close eye on BA.2.

More than half of the states in the U.S. have detected BA.2, with a total of 194 confirmed cases nationwide so far, according to a global database of Covid variants. The Centers for Disease Control and Prevention, in a statement Friday, said BA.2 is currently circulating at a very low…