Assessing the prevalence of neutralizing antibodies (NAbs) to SARS-CoV-2 during three years of the COVID-19 pandemic.

The development of COVID-19 vaccines has been an important step in the fight against the pandemic. However, it is still necessary to understand the influence of factors that can alter the immune response. In general, doses need to be updated frequently, and care must be taken to control the virus that is still circulating worldwide. In this study, we evaluated the neutralizing antibodies (NAbs) against SARS-CoV-2 in northeast Brazil. The study was divided into three phases (T1, T2, and T3) and included 297 participants. The three phases occurred in three different years of the pandemic (2021, 2022 and 2023). We obtained higher mean NAbs in T2 and T3 when most of the participants had already completed their vaccination program. No significant difference in the distribution of NAbs and sex was observed (p > 0.05). It was shown that there is a difference in the expression of NAbs in the different amounts of doses, with individuals with no dose obtaining a significantly lower average than those who took the vaccine. Regarding age, the average NAbs were higher with increasing age. In this study, we assess the prevalence of NAbs in three pandemic phases, making it possible to understand the importance of vaccine updating in maintaining immunity.