SARS-CoV-2 Seroepidemiological Investigation in Jordan: Seroprevalence, Herd Immunity, and Vaccination Coverage. A Population-Based National Study.

Background: Population-based serosurveillance is a cornerstone to furthering our understanding of the COVID-19 pandemic at the community levels. In Jordan, four waves (phases) of seroprevalence epidemiological investigations were conducted using representative population-based national samples. This study aims to estimate the population-based seropositivity, herd immunity, and vaccination coverage at the fourth wave. Methods: Multistage sampling technique was implemented to recruit a nationally representative sample for the fourth wave of the seroprevalence investigation (June to August 2021). Electronically collected data utilized a questionnaire on background demographics, chronic diseases, and COVID-19 vaccination history. Also, blood samples were collected to detect the presence of total Anti-SARS-CoV-2 IgM and IgG using Wantai/ELISA assays. Prevalence estimates were presented using percentage and 95% Confidence Intervals (C.I.). Results: There were 8821 participants included in this study, with a mean age of 31.3 years, and 61.7% were females. COVID-19 national seroprevalence and vaccination coverage estimates were 74.1% (95% C.I.: 73.1-74.9%) and 38.4% (95% C.I.: 37.1-39.6%), respectively. Among children, seroprevalence estimates were similar to unvaccinated adults. Among COVID-19 adults, 57.2% were vaccinated. Among vaccinated participants, 91.5% were seropositive, while among unvaccinated, 63.2% were seropositive. By age group, seroprevalence ranged between 53.0% and 86.9%. Seroprevalence estimates were significantly different by gender, vaccination status and dose, and residence. Conclusion: The reported interplay between seropositivity and vaccination coverage estimate seems insufficient to provide herd immunity levels to combat new variants of SARS-CoV-2. Children and healthcare workers seem to be an epidemiologically influential group in spreading COVID-19. As the globe is still grappling with SARS-CoV-2 infection, national seroepidemiological evidence from Jordan calls for more focus on vaccination coverage, especially among epidemiologically vulnerable groups, to optimize herd immunity.

A three-phase population based sero-epidemiological study: Assessing the trend in prevalence of SARS-CoV-2 during COVID-19 pandemic in Jordan.

The evolution of the COVID-19 pandemic in Jordan during the first 10 months of the epidemic was peculiar and can be easily categorized in three different phases: a first period featuring a very low number of reported cases, a second period with exponential growth from August with up to 8000 cases on the 18th November 2020, and a third phase with steady and progressive decline of the epidemiological curve. With the aim of better determine the entity of the population exposed to SARS-CoV-2, the Jordan Ministry of Health with the support of the WHO launched three rounds of the nationwide sero-prevalence survey. Using population proportionate to size (PPS) methodology, around 5000 individuals were selected from all Jordan governorates. Blood samples were collected from all participants and ELISA assays for total IgM, IgG antibodies to COVID-19 were used for testing at the National Public Health Laboratory. Results revealed that seroprevalence dramatically increased over time, with only a tiny fraction of seropositive individuals in August (0.3%), to increase up to more than 20-fold in October (7.0%) and to reach one-third of the overall population exposed by the end of 2020 (34.2%). While non age-specific trends were detected in infection rates across different age categories, in all three rounds of the seroprevalence study two out of three positive participants did not report any sign and/or symptom compatible with COVID-19. The serial cross-sectional surveys experience in Jordan allowed to gain additional insights of the epidemic over time in combination with context-specific aspects like adherence to public health and social measures (PHSM). On the other hand, such findings would be helpful for planning of public health mitigation measures like vaccinations and tailored restriction policies.