Two doses of Pfizer or AstraZeneca vaccines generate an immune response against the Delta variant in 95% of vaccinated patients, even though it is able to evade some laboratory monoclonal antibodies, according to a study published by the scientific journal nature.
The French scientists responsible for the research, however, indicate that the strain is less inhibited by antibodies present in people who have already had covid-19 and have not received any injections or who have received only one dose of the immunizers.
According to the study, the vaccines are three to five times less effective against the Delta variant compared to Alpha, originating in the UK. This is because, in the researchers’ view, the mutations present in the Spike protein, used by the virus to enter cells, of the Delta variant, “potentially modify the binding of the virus to the cell’s receptor, allowing it to partially escape the immune system’s response.”
Analysis of blood from patients who recovered, in the previous 12 months, from covid-19 revealed that they need four times higher antibody concentrations to neutralize the Delta variant compared to the Alpha. However, when vaccinated, these individuals showed immunity above the neutralizing threshold of the variant.
In addition, a single dose of Pfizer or AstraZeneca vaccine was ineffective against Beta and Delta variants. Only 10% of individuals who received just one injection were able to neutralize the Indian variant after one dose.
The researchers studied the antibody and blood serum reactivity of 103 people with a previous infection and 59 individuals vaccinated with one or two doses. The therapeutic monoclonal antibodies analyzed were Bamlanivimab, Etesevimab, Casirivimab and Imdevimab; of which, only Bamlanivimab “lost antiviral activity”.
The Delta variant is already predominant in countries like India – where it was first detected -, Great Britain and Portugal. Furthermore, according to the Pasteur Institute, it is estimated that, within a few weeks or months, it will be the majority strain in all of Europe.
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