What the first studies on the efficacy of the Pfizer vaccine against the delta variant tell us

In Lancet an analysis of how the antibody response varies with the vaccine in response to variants. The spread of that delta, together with the results of the study, suggests rethinking the vaccination strategy

(Photo: John Cameron on Unsplash) Antibodies capable of neutralizing the delta variant (B.1.617.2) in people who have received the Pfizer-Biontech vaccine are few, or rather they are much lower than those capable of contrasting other variants, such as the English one, especially in those who have received only one dose of vaccine. For this reason, the invitation of the researchers behind the discovery is to proceed with the boosters, and perhaps even with a third dose of the vaccine. Even considering the uncertainties regarding the level of antibodies and protection from symptoms and disease.

In fact, premise: as the group of David LV Bauer of the Francis Crick Institute in London who led the research writes in the Lancet, not it is clear how much the reduction of antibody titers impacts on vaccine efficacy. But there are clues that support the idea that the levels of antibodies (and possibly other associated immune responses) also correlate with protection from the disease. Having said that, here is what Bauer's team observed by measuring the amount of neutralizing antibodies (capable of preventing the virus from entering cells) in the blood of 250 people who had received one or two doses of the vaccine, against 5 different variants of the coronavirus. (the original, the D614G, the alpha, beta and delta, the latter three initially identified as English, South African and Indian variants).

First result: the level of neutralizing antibodies decreases with age for all variants and tends to decrease over time after the second dose. Second result: a double dose induces the production of neutralizing antibodies against the original virus in all participants and also against the three variants (with the exception of a handful of people, for the delta and beta variants). But there was a difference in the quantities produced against the variants, and how: the levels of antibodies against the delta were 5 to 8 times lower than those against the original form of Sars-Cov.2, but reductions were also observed for the alpha variant. and beta (2 to 6 times, and 4 to 9 times, respectively, compared to the original virus). Third result: after a single dose, the levels of neutralizing antibodies were low for all the variants analyzed, the researchers continue, but especially for the beta and delta variant (also known as African and Indian), particularly for older people. br>
What we have observed, we read in the paper, leads us to believe that the delta variant, given its growing spread, at an epidemiological level, may represent a challenge for vaccines. And, again, although a single dose - the initial low-end choice of the UK vaccination strategy - is better than nothing, it appears to provide reduced protection against variants, as anticipated. It is necessary, they conclude, to take this into account in the light of the diffusion of variants, proceed with the administration of the second dose and be ready with the third.


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