RESUMEN
BackgroundOur understanding of the global scale of SARS-CoV-2 infection remains incomplete: routine surveillance data underestimates infection and cannot infer on population immunity, there is a predominance of asymptomatic infections, and uneven access to diagnostics. We meta-analyzed SARS-CoV-2 seroprevalence studies, standardized to those described in WHOs Unity protocol for general population seroepidemiological studies, two years into the pandemic, to estimate the extent of population infection and remaining susceptibility. Methods and FindingsWe conducted a systematic review and meta-analysis, searching MEDLINE, Embase, Web of Science, preprints, and grey literature for SARS-CoV-2 seroprevalence published between 2020-01-01 and 2022-05-20. The review protocol is registered with PROSPERO, (CRD42020183634). We included general population cross-sectional and cohort studies meeting an assay quality threshold (90% sensitivity, 97% specificity; exceptions for humanitarian settings). We excluded studies with an unclear or closed population sample frame. Eligible studies - those aligned with the WHO Unity protocol - were extracted and critically appraised in duplicate, with Risk of Bias evaluated using a modified Joanna Briggs Institute checklist. We meta-analyzed seroprevalence by country and month, pooling to estimate regional and global seroprevalence over time; compared seroprevalence from infection to confirmed cases to estimate under-ascertainment; meta-analyzed differences in seroprevalence between demographic subgroups such as age and sex; and identified national factors associated with seroprevalence using meta-regression. The main limitations of our methodology include that some estimates were driven by certain countries or populations being over-represented. We identified 513 full texts reporting 965 distinct seroprevalence studies (41% LMIC) sampling 5,346,069 participants between January 2020 and April 2022, including 459 low/moderate risk of bias studies with national/sub-national scope in further analysis. By September 2021, global SARS-CoV-2 seroprevalence from infection or vaccination was 59.2%, 95% CI [56.1-62.2%]. Overall seroprevalence rose steeply in 2021 due to infection in some regions (e.g., 26.6% [24.6-28.8] to 86.7% [84.6-88.5%] in Africa in December 2021) and vaccination and infection in others (e.g., 9.6% [8.3-11.0%] to 95.9% [92.6-97.8%] in Europe high-income countries in December 2021). After the emergence of Omicron, infection-induced seroprevalence rose to 47.9% [41.0-54.9%] in EUR HIC and 33.7% [31.6-36.0%] in AMR HIC in March 2022. In 2021 Quarter Three (July to September), median seroprevalence to cumulative incidence ratios ranged from around 2:1 in the Americas and Europe HICs to over 100:1 in Africa (LMICs). Children 0-9 years and adults 60+ were at lower risk of seropositivity than adults 20-29 (p<0.0001 and p=0.005, respectively). In a multivariable model using pre-vaccination data, stringent public health and social measures were associated with lower seroprevalence (p=0.02). ConclusionsIn this study, we observed that global seroprevalence has risen considerably over time and with regional variation, however around 40 % of the global population remains susceptible to SARS-CoV-2 infection. Our estimates of infections based on seroprevalence far exceed reported COVID-19 cases. Quality and standardized seroprevalence studies are essential to inform COVID-19 response, particularly in resource-limited regions.
RESUMEN
COVID-19 affected different countries in different ways. Palestine had recorded over 140,000 cases by the end of 2020. The WHO/PNIPH, WHO/EMRO, and the Palestinian MoH carried out a serological survey in Palestine in order to estimate the actual number of COVID-19 infections up to the end of December 2020. A sample stratified by region, district, residence area (urban, rural, and refugee camp), and accounting for gender, was taken from Gaza and the West Bank. Data from participants were also collected, including demographic, socio-economic, and health conditions. The results show that 39% of the Palestinian population (38% of the West Bank and 40% of Gaza) had been infected with COVID-19 by the end of December, almost 10 times the number detected by targeted Rt-PCR testing. Several factors were calculated to be significant such as diabetes, smoking, gender, age, and residence. Summary of findingsThe following table is a summary of all findings presented in this report. The P values in green are below 0.05, which makes the result statistically significant; red is not statistically significant. In binary comparisons (when comparing two numbers), the odds were calculated, meaning how much more likely the presence of seropositivity is if the condition is satisfied. For example, those who were previously diagnosed as COVID-19 positive using Rt PCR were 2.5 times as likely to be seropositive than those who were not diagnosed. O_TBL View this table: org.highwire.dtl.DTLVardef@86dda2org.highwire.dtl.DTLVardef@40e102org.highwire.dtl.DTLVardef@17454b1org.highwire.dtl.DTLVardef@6448cdorg.highwire.dtl.DTLVardef@1e7cb8e_HPS_FORMAT_FIGEXP M_TBL C_TBL
