Dynamics of SARS-CoV-2 seroprevalence during the first year of the COVID-19 pandemic in the Northeast region of Brazil

ABSTRACT

In this household-based seroepidemiological survey, we analyzed the dynamics of SARS-CoV-2 seroprevalence during the first year of the COVID-19 pandemic in Sergipe State, Northeast Brazil, the poorest region of the country. A total of 16,547 individuals were tested using a rapid IgM−IgG antibody test and fluorescence immunoassay (FIA). Seroprevalence rates were presented according to age, sex, and geographic region. A comparative analysis was performed between the results obtained in July 2020 (peak of the first wave), August – November 2020 (end of the first wave), and February – March 2021 (beginning of the second wave). Seroprevalence rates in the three phases were estimated at 9.3% (95% CI 8.5–10.1), 12.0% (95% CI 11.2–12.9) and 15.4% (95% CI 14.5–16.4). At the end of the first wave, there was a rise in seroprevalence in the countryside (p < 0.001). At the beginning of the second wave, we found an increase in seroprevalence among women (p < 0.001), adults aged 20 to 59 years (p < 0.001), and the elderly (p < 0.001). In this phase, we found an increase in estimates both in metropolitan areas and in the countryside (p < 0.001). This study showed an increase in SARS-CoV-2 seroprevalence over the first year of the pandemic, with approximately one in six people having anti-SARS-CoV-2 antibodies at the beginning of the second wave of COVID-19. Furthermore, our results suggest a rapid spread of COVID-19 from metropolitan areas to the countryside during the first months of the pandemic.

KEYWORDS:

• COVID-19
• SARS-CoV-2
• Seroepidemiologic studies

Disclosure statement

No potential conflict of interest was reported by the author(s).

Data Availability Statement

The data that support the findings of this study are available from the corresponding author, upon reasonable request.

Additional information

Funding

The work was supported by the SES/FAPESE/UFS [001].