Thread by @NavroopSingh_

Neutralising antibody activity against SARS-CoV-2 VOCs B.1.617.2 (Delta Strain) and B.1.351 (Beta) by BNT162b2 vaccination (Pfizer Vaccine) - The Lancet thelancet.com/journals/lance…

NAbTs were 5·8-fold reduced against B.1.617.2 relative to Wild-type (95% CI 5·0–6·9), significantly more reduced than against B.1.1.7 (2·6-fold vs Wild-type, 95% CI 2·2–3·1), and on a similar order to the reduction observed against B.1.351 (4·9-fold vs Wild-type, 95% CI 4·2–5·7).

While the final NAbTs against Wild-type, D614G, and B.1.1.7 remained within the quantitative range of our assay (IC50>40), two participants' NAbTs against VOCs B.1.617.2 and B.1.351 dropped below 40 on their later study visit about 3 months after their second BNT162b2 dose.

Notably, the downwards shift in titres was also significant when compared to B.1.1.7 for B.1.351 (p=3·7 × 10−4) and B.1.617.2 (p=1·2 × 10−5), confirming reduced NAb activity against B.1.617.2 relative to the present B.1.1.7 strain after one vaccine dose

These data, together with epidemiological data of B.1.617.2 growth, raise the possibility that this VOC presents a dual challenge of reduced vaccine efficacy akin to the B.1.351 VOC, and increased transmissibility beyond the B.1.1.7 VOC

Indeed, regardless of the absolute vaccine efficacy requirements, peak NAbTs are significantly reduced against VOCs B.1.617.2 and B.1.351 compared with NAbTs against earlier variants, and consequently,

vaccine efficacy on an individual or sub-population level will become more sensitive to reductions in NAbTs occurring as a result of factors aside from virus strain

In the case of single-dose recipients, our data show that NAbTs are significantly lower against B.1.617.2 and B.1.351 VOCs relative to B.1.1.7, implying that although a single dose might still afford considerably more protection than no vaccination,

single-dose recipients of Pfizer vaccine are likely to be less protected against these SARS-CoV-2 variants.

These data therefore suggest that the benefits of delaying the second dose, in terms of wider population coverage and increased individual NAbTs after the second dose,7 must now be weighed against decreased efficacy in the short-term, in the context of the spread of B.1.617.2.

In the longer term, we note that both increased age and time since the second dose of BNT162b2 significantly correlate with decreased NAb activity against B.1.617.2 and B.1.351—both of which are also characteristic of the population in the UK at highest risk of severe COVID-19

Consequently, further booster immunisations of JCVI Priority Groups in the UK and similar groups in other counties, as well as others with lower vaccine-induced NAbTs than the cohort of BNT162b2 recipients studied here

ideally with modified vaccines that induce NAbs that broadly neutralise emerging VOCs) are more likely to be required to maintain the highest levels of NAbs in regions where B.1.617.2

Summary of Thread:

> Pfizer Vaccine Antibodies is significantly neutralised against Delta Variant B.1.617.2 upto 5.8 folds compared to 2.8 Folds against Alpha Variant B.1.1.7 & 4.9 Folds against the Beta Variant B.1.315

> Single Dose Pfizer gives very less protection against B.1.617.2 & B.1.315 compared to B.1.17. Two doses gives u sufficient protection but its far less than against Original strain that chances on Reinfection remain.

> Given the mutation of B.1.617.2 countries might have to rethink reducing the dosage time between two dosages as one dose gives insufficient immunity against the mutant strain.

> Also plan for Booster shots for Vulnerable section soon given B.1.617.2 neutralises Antibodies.