The omicron subvariant BA.2 is more transmissible than the original strain, though vaccinated people are less likely to spread it to others, according to a Danish study published Jan. 30 in the medical preprint server MedRxiv.
Researchers analyzed data on nearly 18,000 people from 8,541 Danish households between Dec. 20, 2021, and Jan. 18. The research has not been peer reviewed.
Four study findings:
1. For people exposed to BA.2 in their household, the likelihood of contracting COVID-19 within seven days was 39 percent, compared to 29 percent for those exposed to BA.1, the original omicron strain.
2. People had an increased risk of infection from the BA.2 strain regardless of vaccination status, "indicating an inherent increased transmissibility of the BA.2 subvariant," researchers said in a Jan. 31 news release.
3. Relative to the original omicron strain, vaccinated individuals had a higher increase in susceptibility of infection from BA.2 compared to unvaccinated people, which suggests the subvariant can evade immune protection from vaccines better than BA.1, CNBC reported.
4. Vaccinated people infected with BA.2 transmitted the virus less than vaccinated people infected with the original strain.
"We conclude that omicron BA.2 is inherently substantially more transmissible than BA.1, and that it also possesses immune-evasive properties that further reduce the protective effect of vaccination against infection, but do not increase its transmissibility from vaccinated individuals with breakthrough infections," researchers said.