Thread by @macroliter

Yes.. BA.2 is increasing in USA.. but total is still only 180 entries in GISAID from all of USA, while BA.1 is at 132,497..
If we filter to only samples collected since Jan 10, it's: 127 BA.2 in USA versus 16,407 BA.1

If BA.2 takes over as % of new U.S. cases, as seems plausible, this will happen much more slowly than Omicron displacing Delta... Not maybe as slow as AY4.2 (LOL!) but I'd guess it'll take at least another month.. & will coincide w/ overall waning of the Omicron (BA.1+BA.2) wave

Keep in mind that although BA.1 and BA.2 might compete with each other, BA.2 didn’t evolve / emerge to escape anti-BA.1 antibodies..

So, most immunocompetent people who recently recovered from BA.1 infection won't be friendly hosts for BA.2, h/t @ENirenberg..

And even if NTD differences allow some escape from BA.1 antibodies, remember: even Dec 2019 Spike immunization induces antibodies that can protect against #Omicron..

https://twitter.com/trvrb/status/1487105435903553537?s=20&t=rfj5h-RNFjp5Wz6sr66Tig

In other words, it's rather implausible that most people's anti-BA.1 antibodies wouldn't protect them from BA.2 infection (via direct neutralization).. Not to mention other layers of immunity being cross-reactive enough to nip in the bud most nascent re-infections..

That said many people on Twitter seem to think "the exception IS the rule".. and news reports often frame things this way too.. Omicron symptomatically reinfecting someone who caught Omicron already, and causing disease-- yeah that will happen but probably only quite rarely

There DEFINITELY are individuals who seem to be predisposed to catching COVID-19 multiple times or to being re-infected.. probably lots going on there.. (likely genetics + age + lifestyle and other variables that play into it)..But that is not the norm for most people.

Thank you to all GISAID community submitters for rapidly generating and sharing their SARS-CoV-2 genome sequencing data.. without this national and international collaboration we would not have good data on variants..

And without the @GISAID community we wouldn't have gotten a timely and invaluable EARLY warning from people like @drSikhulileMoyo @Tuliodna @houzhou and Alan Tseng (Hong Kong) about this new variant Omicron.

It is just incredible to see how much Omicron has grown since it was first announced on Nov 25, 2021.. can you believe that was only 6⃣4⃣ days ago?