Thread by @profshanecrotty

The speed of progress to update COVID vaccines is just incredible. Moderna shipped an updated B1351 (South Africa variant) RNA booster vaccine candidate to the American NIH Vaccine Research Center last week for immediate human Phase 1 clinical trial. 🧵

businesswire.com/news/home/2021…

The booster vaccination plan is reasonable, and such a variant booster vaccine could be available quite quickly with an immunogenicity and safety trial.
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The approach seems likely to elicit high amounts of crossprotective antibodies, based on recent reports of very high antibody responses after 1-dose COVID RNA vaccine immunization of people with previous COVID disease. And the T cell responses will be conserved and boosted.
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And Novavax announced they have also started work on a B1351 variant vaccine, with their protein technology.
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npr.org/2021/03/02/972…

Adding info on the rationale for a variant COVID vaccine booster: I certainly think the lab-based and clinical trial data so far warrant development of a better matched vaccine. The main concern in America right now is 'original' SARS2 and the B117 variant (UK variant). But...

But B1351 (South Africa variant) or related variants are the bigger long term worry. For these reasons:

🔵 No vaccine has a reported efficacy against B1351 for symptomatic COVID better than ~60%.

🔵 There is no direct evidence so far of vaccines able to reduce B1351 viral loads enough to prevent asymptomatic cases and/or prevent transmission.

🔵 The neutralizing Ab potency drops for all vaccines reported so far.

🔵 Antibody potency also drops for COVID convalescent serum, dramatically by some assays.

🔵 Several of the B1351 Spike mutations are clearly antibody escape mutations (whether or not they co-evolved for other purposes also)

🔵 There is clearly convergent evolution for a series of the most important mutations in B1351.

🔵 And what if one more new viral mutation degrades the protective immunity even more to the current vaccines?

🔵 There clearly are antibodies that can recognize and neutralize B1351 well, so one would expect a matched vaccine to B1351 to generate great neutralizing antibodies

🔵 A booster vaccine will quite possibly give protection against COVID even better / longer than the original vaccine, because of a big jump in the immune response with a 3rd exposure.

On the flip side (not needing new vac) :
🔴 The current COVID vaccines (or most of them) may very well protect excellently against B1351-like variants for hospitalization-level COVID and deaths. The J&J 1-dose vaccine looks that way. There aren't direct data for the RNA vaccines

(and not a big enough trial for Novavax in SA)

But, still the best case scenario is to have great COVID vaccines that prevent almost all symptomatic infections--and prevent virus transmission, both preventing more cases and helping prevent future variants. Overall, those outcomes are best for the individual and the community.

And we know COVID vaccines can do that! So it makes sense to plan for updated COVID booster vaccines.

@threadreaderapp unroll please