Thread by @sailorrooscout

A recent study shows Pfizer’s and Moderna’s vaccines are protective against SARS-CoV-2 variant P.1. Despite some reduction, loss of neutralizing activity was modest (2.8 & 2.2 fold) & reduction was not as striking as observed prior against B.1.351. 🧵
biorxiv.org/content/10.110…

To study this, researchers created a VSV-based SARS-CoV-2 pseudovirus with all 10 mutations of the P.1 variant (B.1.1.28 lineage) and assessed its susceptibility to neutralization by neutralizing mAbs, convalescent plasma of patients, and vaccinee sera.

For thoroughness, activity of four mAbs including REGN10987 (imdevimab), REGN10933 (casirivimab), LY-CoV555 (bamlanivimab) and CB6 (etesevimab), six NTD mAbs, convalescent plasma of patients infected in Spring of 2020, and sera of Moderna and Pfizer recipients were analyzed.

What researchers found was that P.1 was resistant to neutralization by several RBD-directed mAbs, and convalescent plasma and vaccinee sera show a loss of neutralizing activity against P.1, but the diminution is not as great as that reported against B.1.351.

Therefore, the threat of increased re-infection or decreased vaccine protection posed by P.1 may not be as severe as B.1.351. To reiterate, it would take a large amount of genetic diversity to completely understand render these vaccines useless. Why? Vaccines are polyclonal.

Unlike monoclonal antibody (mAb) therapies, vaccines (especially these using the whole spike protein) make POLYCLONAL antibody responses. This means that the antibodies created will be able to bind the Coronavirus spike in multiple places not just one.

The magnitude of the loss of neutralizing activity was modest (2.8 fold, Moderna; 2.2 fold for Pfizer) therefore the neutralizing titers against the Brazilian variant P.1 still remain above levels that are expected to be protective. To put it into perspective, these vaccines were

found to still be above protective levels against B.1.351 with a (8.6 fold, Moderna; 6.5 fold, Pfizer) loss of neutralizing activity. So keep that in mind when you view this study. We have updated boosters being tested in an abundance of caution for these and future variants.

Needless to say, we are in a positive position and P.1 might not be as much of an initial threat as it was portrayed to be when compared to B.1.351 and B.1.1.7. In short, yes, these vaccines are still effective as expected with those that utilize the entire spike protein.

This corresponds to my thread from yesterday concerning cell-mediated immunity against these VOCs.

https://twitter.com/sailorrooscout/status/1366742151351132168