ABSTRACT
Background: In the last two years the pandemic Coronavirus Disease 19 (Covid19), caused by the virus SARS-CoV- 2, described for the first time in Wuhan (China) at the end of 2019, has caused over 359 million cases of infections and 5 million deaths worldwide. To fight this emergency, the pursuit of science has focused on vaccines development against SARS-CoV- 2, including the vaccine BNT162b2. This vaccine contains mRNA translating for SARS-CoV- 2 spike protein wrapped in lipid nanoparticles and its use was approved at the end of 2020. It has been proved that both the BNT162b2 vaccine and the SARS-CoV- 2 infection result in the production of neutralizing antibodies but remains to be clarified the duration of these responses, also versus variants of concern. Method(s): The present study aimed to prospectively analyse and correlate the antibody response and the neutralization capability induced by vaccination with BNT162b2 in a cohort of Sardinian subjects, including a group previously Cov2 infected. Each participant was evaluated for serum SARS-CoV2 Ab IgG RDB, 7 (T1) and 30 (T2) days after the second inoculum of BNT162b2, with chemiluminescent immunoassays (CLIA) and microneutralization assay (MNA) determining the highest serum dilution protecting 90 % of the infected wells. Result(s): All the participants, with or without previous infection, developed a positive antibody response (IgG anti-RBD > 1 AU/ml) within 7 and 30 days from the second vaccine dose and a strong correlation was found between IgG antibody levels and neutralizing activity. A strong difference was observed between the antibody levels of the naive subjects and the ones previously infected, specifically the antibody levels were higher (both at T1 and T2) in the latter group. No significant antibody differences were found for gender and age groups. In addition, there were no significant differences in antibody titre between healthy and immune-mediated subjects. Conclusion(s): In conclusion, this study confirms observed differences in vaccine responses between infection-naive and subjects with history of natural infection, with the presence in the second group of a significantly higher neutralizing and anti-RBD antibody titer. It also demonstrates the strong correlation between anti-RBD antibody titre and neutralizing activity, without significant differences between healthy subjects and subjects with immuno-mediated disease in the short-term. Further follow-up is ongoing in this cohort.