Previously Infected Vaccinees Broadly Neutralize Variants of Concern

Researchers from the USA have conducted a study demonstrating the effectiveness of first-generation vaccines at protecting against variants of SARS-CoV-2 in individuals who have previously been infected with the virus. The team assessed levels of neutralizing antibodies against variants of SARS-CoV-2 before and after two doses of the Pfizer-BioNTech vaccine in ten individuals who had been infected with the original strain of the virus before vaccination. These neutralizing titers were compared with those of people who also received the two vaccines but had not previously been infected.

The researchers found that vaccination boosted pre-existing levels of antibodies against the viral spike protein 10-fold in the previously infected individuals, but not to levels that were significantly higher than those of previously uninfected vaccinees. However, vaccination increased neutralizing antibody titers to higher levels in previously infected individuals versus uninfected vaccinees against the original strain of SARS-CoV-2 and three variants of the virus. Neutralizing antibody titers from the previously infected vaccinees were more than five times higher against the B.1.1.7 variant that emerged in the UK, more than six times higher against the B.1.351 lineage that emerged in South Africa and more than four times higher against the P.1 lineage that emerged in Brazil. In the previously infected individuals, vaccination generated significantly higher levels of neutralizing activity against every SARS-CoV-2 lineage tested than in the previously uninfected vaccinees.

Neutralizing antibody titers were 3.5 times higher against the original lineage, 5.2 times higher against B.1.1.7, 6.5 times higher against B.1.351,0 and 4.3 times higher against P.1. Importantly, there was no significant difference between the post-vaccination neutralizing antibody titers against the B.1.351 variant in previously infected individuals and those against the original viral strain in previously uninfected individuals.

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