Seroprevalence of SARS-CoV-2 Antibodies among Vaccinated and Non-Vaccinated Adults in the West Bank: Results of a Repeated Cross-Sectional Study.

Seroprevalence studies provide an accurate measure of SARS-CoV-2 spread at a population level and the number of undiagnosed individuals. Repeated cross-sectional sero-studies are encouraged to monitor the spread of the virus. The aim of this study is to assess the seroprevalence rate among a random sample of Palestinians residing in the West Bank region of Palestine, especially among those who were not vaccinated and not diagnosed. The study was able to assess the prevalence of asymptomatic cases among the Palestinian adult population. The study also focused on measuring the percentage of adult Palestinians who accepted to get vaccinated across gender and age groups. Methods: This second round cross-sectional study involved 1451 participants, who agreed to be interviewed and answer the questionnaire, where 910 of them agreed to participate in the sero-study and donate a blood sample to be tested for antibodies. The sample was randomly selected from the adult population, 18 years or older, living in the West Bank region of Palestine. Serological tests for 910 adequate serum samples were performed using immunoassays for the detection of antibodies against SARS-CoV-2. Sociodemographic information and medical history data were collected. Results: Study findings indicate that as of October 2021, there was a seroprevalence rate of 75.9% (30% due to infection with COVID-19 virus and 45.9% due to vaccination) with 95% CI (73.1−78.7). The results indicate that the prevalence of antibodies among those who are unvaccinated and undiagnosed was 45.2% with 95% CI (39.9−50.5%). The average age of participants was 37.6 years old. A total of 49.2% were females, and 50.8% were males. In relation to COVID-19, 13.6% of respondents reported getting infected by COVID-19 with statistically significant difference (p-value = 0.001) between males (10.7%) and females (16.5%). In terms of vaccination, 52.8% of respondents reported getting vaccinated with an important difference between males (64.3%) and females (40.9%), (p-value < 0.01). Conclusions: Our findings reveal a drastic rise in seroprevalence of SARS-CoV-2 antibodies due to infection and vaccination. This information is useful for assessing the degree of herd immunity among the adult population and provides better understanding of the pandemic. Population-based seroprevalence studies should be conducted periodically to monitor the SARS-CoV-2 seroprevalence in Palestine and inform policy makers about the efficacy of the surveillance system and the public compliance with vaccination policies especially among females.