Thread by @DrEricDing

⚠️SUB-VARIANT SURGING—Omicron 2.0 is rising—the #BA2 sublineage of #Omicron has *tripled* in one week, dislodging the old Omicron from total dominance—BA2 now at 3.6% and climbing fast. Expect to be dominant by March. Omicron reinfections are possible. 🧵 covid.cdc.gov/covid-data-tra…

2) Omicron subvariant #BA2 now seems to be surging nationwide (pink), especially in the coastal regions of the Us the fastest. This means it’s not a fluke increase. US’s #BA2 trend will follow Europe’s rise for sure.

3) I’ve been worried about #BA2 for a while. In 3rd week of January, it was rising in Denmark— it’s now near total dominant in Denmark.

https://twitter.com/DrEricDing/status/1485310469451792388

4) Multiple studies show the #BA2 subvariant is much faster transmission than old Omicron. Some say 30% some say ~90-120%, and some say 150% (1.5 time more).

https://twitter.com/DrEricDing/status/1485354857339011080

5) Who said #BA2 is 1.5 times more contagious? Denmark’s CDC @SSI_dk said so—and they warned it was extending Denmark’s Omicron wave much longer. Same thing is going to happen in the US which is much much less vaccinated.

https://twitter.com/DrEricDing/status/1486770004796362752

6) other tricky thing is that #Omicron #Ba2’s PCR looks like almost any other non-BA1 Omicron because the SGTF shortcut PCR won’t work on BA2. Thus it’s hard to tell apart BA2 from Delta variant without genome 🧬 sequencing.

https://twitter.com/DrEricDing/status/1485473547971698691

7) Virus researcher & chief physician of 🇩🇰’s CDC @SSI_dk says you can get **reinfected with #BA2 sub-variant** of #Omicron after being infected with Omicron BA.1. ➡️ This is why we shouldn’t risk COVID or chase mass infection. nyheder.tv2.dk/2022-01-21-ny-…

8) It’s also surging in UK 🇬🇧 as well. #Ba2 d doubled in one week. It’s also surging in Netherlands and in Germany and elsewhere. It’s everywhere now- and quickly displacing the old Omicron 1.0.

https://twitter.com/drericding/status/1489647602773671942

9) How different is #Omicron BA2 from BA1? #BA2 has **17 additional mutations** that BA1 doesn’t have! There is also a BA3 but that one doesn’t have much difference beyond BA1 and BA2.

HT @WmHaseltine

10) Notably, “Each of BA1/2/3 variants is as different from one another as Alpha, Beta, Gamma, and Delta are from one another”! says @WmHaseltine

11) BA2 #Omicron is not a child-lineage of BA1 #Omicron. They are more like “cousins” that branched off earlier - hence they are much more different than parent-child versions of each other. This is also why reinfections could be higher.

12) If you still have any doubt in your mind about #BA2 being a 2.0 Omicron that will displace the old Omicron and cause a new surge— just look at how #BA2 (aka ‘Omicron 21L’ in the charts) is surging like mad across multiple countries (& this is just late Jan data!). Get ready.

13) 🇬🇧 data also shows a higher secondary attack rate in households for #BA2 versus the old BA1 Omicron. And the growth rate is indeed more than doubling per week. Exponential rise will beget exponential trouble - earlier Omicron immunity clearly isn’t slowing it much—not good.

https://twitter.com/DrEricDing/status/1488799381138681856

14) Now the real bad news— two new studies say “immunity based on #Omicron-infection is weak for (another) Omicron reinfection” — if unvaccinated ⚠️

This means protection from your earlier Omicron may not be great if unvaccinated! 👀

https://twitter.com/yaneerbaryam/status/1487814472169361410

15) Some relatively good news on #BA2 is that it seems to responds similarly to vaccines as BA1– but it responds well only to 3 vaccine shots if you get a booster. Without booster, the symptomatic efficacy is very poor —13% and that’s not even significantly different from 0.

https://twitter.com/DrEricDing/status/1488801542757040129

16) Update on UK #BA2– it has doubled again and it’s now likely ~17% of all cases in England. And it has a much higher attack rate — altogether bad.

https://twitter.com/AlastairGrant4/status/1491359003384840195

17) the reinfection risk of #Omicron is real. We need to take it seriously folks. Don’t feel like you’re invulnerable. That leads to blase attitude and risky behaviors.

https://twitter.com/DrEricDing/status/1487833014965055495

18) Further—“results indicate that Omicron infection enhances preexisting immunity elicited by vaccines, ➡️but on its own **may NOT induce broad, cross-neutralizing humoral immunity in unvaccinated** individuals.” ⚠️

Don’t risk #Omicron BA2 if unvaxxed! medrxiv.org/content/10.110…

19) It now seems the @WHO is getting very concerned about #BA2 variant outcompeting and displacing old #Omicron. @mvankerkhove is now warning about likely looming surge. We must be vigilant.

HT @Cleavon_MD.

20) It is now 100% clear that the @WHO needs to declare #Ba2 a high risk “variant of concern”. Dear @mvankerkhove @doctorsoumya @DrTedros @gabbystern @DrMikeRyan — please make it so. VOC declaration of BA2 now ASAP!

See 🧵 below.

https://twitter.com/drericding/status/1494746690787717124