So... BA.2. Not a 'new Omicron subvariant' as some have called it but more like a shier sister that also came from South Africa and was first detected in November.
There are suggestions if might be more contagious than BA.1, maybe 50% more according to Danish data. This comes as a surprise since it's antigenically very similar to BA.1 if not *less* able to evade antibodies. This would suggest something else is going on. Perhaps it was always in the background, and our singular focus on SGTF to detect Omicron might have allowed it to remain under the radar. Or perhaps the ORF1a mutations that are unique to BA.2 make it fitter instead.
On the other hand, it doesn't seem to be more or less virulent than the other Omicron strain according to Danish data. A look at India and the Philippines also suggests there isn't anything unusual going on. And I would expect BA.1-infected people to have near-total immunity to it, especially the ones who were also vaccinated, same with protection against severe disease from vaccines only.
Can it cause another wave in places that are past 'standard' Omicron? I doubt it. BA.1 is so contagious already that there wouldn't be more than a few percent of people vulnerable left by the time it becomes dominant unless third-dose protection wanes significantly between now and then.
