Introduction:

The aim of this study was to measure anti-SARS-CoV-2 immunity of hospital workers after a completed 2-dose Pfizer-BionTech vaccination, and to examine factors potentially associated with immunity status. Side effects of the vaccine were also studied.

Method:

This was a cross-sectional study of a representative sample of General University Hospital of Castellon workers, vaccinated with two doses in January and February 2021. We measured IgG antibodies against protein N (IgG-NP), IgM against protein S (IgM-S), and quantitative levles of IgG against protein S (IgG-Quant) one month after the last dose. We obtained information on demographic, risk factors, and vaccine side effects via a self-completed questionnaire. For the statistical analysis we used multiple regression models.

Results:

Two hundred seventy-five workers participated (96.8%, 275/284). Positive IgG-Quant, IgM-S, and IgG-NP were 99.6%, 14.9% and 4.4%, respectively. Adjusted IgG-Quant levels increased significantly with obesity, nonsmoking status, positive IgM-S, and/or IgG-NP. The prevalence of IgM-S was higher in males, and associated with the same factors as those for IgG-Quant. Among those with a history of COVD-19 infection, 42.9% did not have IgG-NP. Overall 86.5% of participants had side effects, which were associated with positive IgG-NP, high IgG-Quant levels, younger age, and being female.

Conclusions:

All but one participant developed immunity. Those who had suffered from COVID-19 infection had higher antibody levels. A high proportion of participants had mild secondary effects, especially those with previous COVID-19 infection.

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