Humoral immune response after the Pfizer vaccination

Pfizer vaccine consists of a lipid nanoparticle shell to deliver a mRNA to the cytoplasm of host cells. Based on this technique, cells synthesize the SARS-CoV-2 spike protein, which shows the strongest immune effect. Spike protein is displayed on the host cell surface and is recognized by the immune system. Thirty-four colleagues were followed to investigate their humoral immune response. Blood samples were collected before vaccination, at 12 days after the first dose and 14 days after the second dose. Seven different COVID-19 serology tests were performed: two types of IgG;of IgM;of IgA and anti-S1-RBD IgG neutralizing antibody levels. Recruited participants were allocated into 3 groups: 1) 26 were seronegative, 2) 5 had been previously contacted with SARS-CoV-2 infection and 3) three subjects had an ongoing, asymptomatic COVID-19 infection. Twelve days after the first dose, who previously had not been in contact with the virus, 73% had positive anti-S1/S2 IgG and 81% demonstrated anti-S IgA antibodies. In those who had been contacted with the virus showed unusually high levels of anti-S1/S2 IgG and anti-S IgA. Individuals with ongoing infection had serious adverse symptoms after vaccination. At 14 days after the second dose, 95% from the first group had high anti-S1/S2 (>100 AU/ml) and high neutralizing antibody levels. Anti-S IgA was positive among all of them, while anti-S IgM antibodies were detected in 75% of the cases. In group 2, antibody levels did not rise further, instead, in some cases the antibodies decreased drastically. In conclusion, Pfizer vaccine effectively triggers the development of the humoral immune response. According to our study, vaccination is not recommended during an ongoing infection and for patients with previous COVID-19 infection and high antibody levels, thus the second dose of vaccination should be considered at a later time than usual.