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. 2021 Dec 17;12:793191. doi: 10.3389/fimmu.2021.793191

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Copyright © 2021 Tarkowski, de Jager, Schiuma, Covizzi, Lai, Gabrieli, Corbellino, Bergna, Ventura, Galli, Riva and Antinori

This is an open-access article distributed under the terms of the Creative Commons Attribution License (CC BY). The use, distribution or reproduction in other forums is permitted, provided the original author(s) and the copyright owner(s) are credited and that the original publication in this journal is cited, in accordance with accepted academic practice. No use, distribution or reproduction is permitted which does not comply with these terms.

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Neutralization of SARS-CoV-2 infectivity according to viral variant and subject infection and BNT162b2 vaccination history. (A) In unvaccinated individuals hospitalized with SARS-CoV-2 (n=8), mean neutralization effectiveness against the B.1 strain (set as 100%; titer=225 ± 135 fold dilution) was reduced by 33% against the Gamma variant (titer=150 ± 90) and by 67% against the Delta variant (titer=75 ± 45). In SARS-CoV-2-naïve subjects (n=8) who received the 2-dose BNT162b2 vaccination series, neutralizing effectiveness was similar against the three SARS-CoV-2 variants with inhibitory activity against the B.1 strain (set at 100%; titer=115 ± 39) maintained at 100% against the Gamma variant (titer=115 ± 39), and modestly 23% lower against the Delta variant (titer=90 ± 30). By far the strongest neutralizing ability was elicited in volunteers (n=3) who had previously been diagnosed with and recovered from Covid-19 and then received a single BNT162b2 vaccine dose. In this Covid+/1 Vaccine Dose group, the average maximal neutralizing titer against the B.1 strain (set at 100%; titer=1360 ± 349) were reduced by 29% against the Gamma variant (titer=960 ± 240; p>0.05) and by 74% against the Delta variant (titer=360 ± 69; p=0.048). (B) Individuals who had previously recovered from Covid-19 and then received a single vaccine dose developed significantly higher neutralization titers against B.1 and Gamma strains when compared to Covid-naïve individuals who received 2 vaccine doses. Neutralization of the Delta variant was also numerically 4-fold higher in Covid+/1 Vaccine Dose subjects versus Covid-naïve/2 Vaccine Dose subjects, and 5-fold higher than in unvaccinated individuals who were hospitalized for Covid-19, but these differences did not attain statistical significance. Neutralization capacity of the plasma of subjects hospitalized with Covid-19 did not remarkably differ from neutralization by Covid-naïve individuals who received the both vaccine doses, for all SARS-CoV-2 strains studied. Shown are mean values ± SEM.