# Seroepidemiology of Severe Acute Respiratory Syndrome Coronavirus 2 Infection in Blood Donors from Western Romania, August–September 2023

## TL;DR

This study found that 89.69% of blood donors in western Romania had been exposed to SARS-CoV-2, with unvaccinated individuals and rural residents more likely to test positive.

## Contribution

The study provides updated seroprevalence data and identifies vaccination status and residence area as key factors in SARS-CoV-2 exposure.

## Key findings

- The overall SARS-CoV-2 seroprevalence among blood donors was 89.69%.
- Unvaccinated individuals were more likely to test positive compared to vaccinated participants.
- Rural residents had significantly higher odds of seropositivity than urban residents.

## Abstract

Serological testing for SARS-CoV-2-specific antibodies, particularly those targeting the nucleocapsid protein, plays a key role in assessing past infection and estimating population-level seroprevalence. The seroprevalence of nucleocapsid antibodies against SARS-CoV-2 was evaluated in 1048 blood donors using the Elecsys Anti-SARS-CoV-2 electrochemiluminescence immunoassay. Participants completed a questionnaire to assess risk factors, symptoms during SARS-CoV-2 infection and vaccination status. The overall SARS-CoV-2 seroprevalence was 89.69%. Seroprevalence was not significantly associated with gender or age. In multivariate logistic regression, most investigated risk factors showed no significant association with seroprevalence. However, residence area and vaccination status were independently associated with SARS-CoV-2 seropositivity. Donors from rural areas had significantly higher odds of seropositivity (aOR = 1.68; 95% CI: 1.01–2.79; p = 0.045) compared to those from urban areas. Unvaccinated individuals were more likely to test positive for SARS-CoV-2 compared to vaccinated participants (aOR: 2.59; 95% CI: 1.35–4.99; p = 0.004). After three years of the COVID-19 pandemic, the prevalence of SARS-CoV-2 among blood donors was remarkably high, indicating that the vast majority of this population group had been exposed to the virus. This study highlights the risk factors for SARS-CoV-2 infection and the differences in antibody prevalence between vaccinated and unvaccinated individuals. Our findings underscore the pivotal role of vaccination in controlling the pandemic and provide valuable insights for policymakers in designing targeted strategies to curb future SARS-CoV-2 transmission.