Covid: Pfizer vaccine less effective against the South African variant, a study finds

Published by Laurent P. · Published on 12 April 2021 at 14h26 · Updated on 12 April 2021 at 15h09
Pfizer covid vaccine is said to be less effective against the South African variant... This is at least what an Israeli study found on the matter, stating this strain is likely to "break through" the vaccine. The study shifts focus of the results from the previous study carried out by the American laboratory, explaining their vaccine was working for at least six months against all variants, and especially the South African strain.

A study has been recently issued and assesses the effectiveness of Pfizer Covid vaccine against the variants of the virus... According to this study, published on April 10 by searchers from the University of Tel-Aviv and Clalit - the country's first healthcare insurer - put not peer-reviewed yet, the Pfizer/BioNTech vaccine is said to lack effectiveness against the South African variant, the strain being likely to "break though" the vaccine to some extent.

What was the study about? It compared two groups: one including 400 people not given doses of vaccine and who have caught the virus, and another group with 400 people as well, given one or two doses of the Pfizer vaccine, and who also tested positive to the virus ahead of the study. Searchers noticed that in group 2, in 150 people - those given two doses of vaccine - "the South African variant [...] was found to be eight times more prevalent among vaccinated patients".  Tel Aviv University's Adi Stern told AFP: "This means that the South African variant is able, to some extent, to break through the vaccine’s protection".

The Israeli study suggests the Pfizer/BioNTech vaccine provides less protection against the South African variant than the original coronavirus. But given the very small sample size of people infected with this strain - eight people - it is stastistically insignificant.

A less effective vaccine yet protecting against the South African variant

This study changes results released on April 1, by the American laboratory… According to Pfizer's latest analyzes, their vaccine is working against the most-spread variants, up to 91%, as reported by our peers from Wall Street Journal. They give more details on the immunity lifespan after the second doses has been injected: "Pfizer-BioNTech COVID-19 vaccine, BNT162b2, was 91.3% effective against COVID-19, measured seven days through up to six months after the second dose", they explain. Results coming from post-vaccination observations in volunteers in the clinical trial that led to the creation of the vaccine, and going on to determine if immunity can be longer.

Results also echo a study  conducted this past February and in vitro by American scientists and released in Nature Medicine - Pfizer vaccine is effective against coronavirus variants - whether they are the UK, South-African or Brazilian strains. At the heart of questions, a specific mutation, E484K, found in the South-African and Brazilian variants, and that has started to appear in a strain of the UK variant.

What was the study about? As explained, the laboratory scientists have synthesized  complete pseudoviruses they put with antibodies collected in the blood from vaccinated patients. The study is different from the previous studies as they mostly suggested that antibodies identified as the most effective to stuck to the virus and blockd it could barely hang to the virus and prevent it from entering cells. But there is a problem: these antibodies were from patients who recovered and who were not vaccinated, and then put in front of the virus. The very opposite of this new study using antibodies from vaccinated volunteers' blood.

Anyway, "there is legit worries as of the effectiveness of antibodies against these variantsCNRS head of research at the Architecture et fonction des macromolécules biologiques laboratory in Marseille Etienne Decroly tells Le Figaro.

And results are clear: the effectiveness is similar - and even identical - when it comes to the vaccine in comparison with the "standard" strain of the virus. "These results are all the more so as encouraging this method only measures the effectiveness of a part of the immune systemCNRS head at the CRCINA (Nantes-Anger Oncology and Immunology Research Center) Bruno Pitard explains. And for good reason: the vaccine does not only cause antibodies production, but activates "any 'cell' response against the virus which is not being measured in this work", Le Figaro says.

Results on the vaccine effectiveness against the South African variant already highlighted in January

This Friday January 8, 2021 Pfizer issued a release saying their vaccine – the first vaccine to have been approved in France and other countries around the world – is effective against the two new strains of the virus, one from the United-Kingdom, the other from South Africa. The effectiveness has been assessed after a laboratory study has been completed by the pharmaceutical group, as well as by scientists from the University of Texas.

But, a new preliminary study - released by South-African doctors on Januayr 19 - disappoints all hopes. And for good reason, this variant is "largely resistant to neutralizing antibodies elicited by infection with previously circulating lineages" and seems to "have implications for the effectiveness of SARS-CoV-2 vaccines" as they are "principally based on immune responses to the spike protein".

Who could Pfizer vaccine (and other vaccines) ineffective against this variant? Because of the mutation noticed - and feared by scientists - simply called E484K and able - according to this new study - to prevent antibodies from recognizing the virus and therefore from neutralizing it. Vaccine being based on the Spike protein, it could be useless.

As for the study carried out by Pfizer earlier this month, it says the vaccine is able to “neutralize” the virus including the N501Y mutation of the protein, which is the case in the two variants found in France. “The antibodies from people who have received the Pfizer-BioNTech COVID-19 vaccine effectively neutralize SARS-CoV-2 with a key mutation that is also found in two highly transmissible strains” the laboratory explained. Long story short, only a very small part of the virus protein (1%) has mutated, and not the entire virus. Hence the affirmation of the virus effectiveness.

The study has been conducted on several blood samples from volunteers given the vaccine, but remains insufficient to firmly assess the confirmed effectiveness on the two variants. Why sharing the results, then? Scientists explain that the results of the study yet could help relieve fears on vaccines inoculated to millions of people around the world as part of the fight against the pandemic. Other studies are to be conducted to confirm these preliminary results.

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