Antibody prevalence for SARS-CoV-2 following the peak of the pandemic in England: REACT2 study in 100,000 adults

Abstract

Background England, UK has experienced a large outbreak of SARS-CoV-2 infection. As in USA and elsewhere, disadvantaged communities have been disproportionately affected. Methods National REal-time Assessment of Community Transmission-2 (REACT-2) seroprevalence study using self-administered lateral flow immunoassay (LFIA) test for IgG among a random population sample of 100,000 adults over 18 years in England, 20 June to 13 July 2020. Results Completed questionnaires were available for 109,076 participants, yielding 5,544 IgG positive results and adjusted (for test performance), re-weighted (for sampling) prevalence of 6.0% (95% CI: 5.8, 6.1). Highest prevalence was in London (13.0% [12.3, 13.6]), among people of Black or Asian (mainly South Asian) ethnicity (17.3% [15.8, 19.1] and 11.9% [11.0, 12.8] respectively) and those aged 18-24 years (7.9% [7.3, 8.5]). Care home workers with client-facing roles had adjusted odds ratio of 3.1 (2.5, 3.8) compared with non-essential workers. One third (32.2%, [31.0-33.4]) of antibody positive individuals reported no symptoms. Among symptomatic cases, the majority (78.8%) reported symptoms during the peak of the epidemic in England in March (31.3%) and April (47.5%) 2020. We estimate that 3.36 million (3.21, 3.51) people have been infected with SARS-CoV-2 in England to end June 2020, with an overall infection fatality ratio of 0.90% (0.86, 0.94). Conclusion The pandemic of SARS-CoV-2 infection in England disproportionately affected ethnic minority groups and health and care home workers. The higher risk of infection in these groups may explain, at least in part, their increased risk of hospitalisation and mortality from COVID-19.

Population-based seroprevalence of SARS-CoV-2 is more than halfway through the herd immunity threshold in the State of Maranhão, Brazil

“…21 Therefore, as the test we used is more sensitive and specific, we were able to detect a higher percentage of persons with antibodies against SARS-CoV-2 with few false-positive results. The distribution and percentage of self-reported symptoms among the infected in our survey were similar to what has been reported by others, 9,11,32 providing further evidence that a high falsepositive rate in our study is unlikely.…”

Epidemiology of SARS-CoV-2

“…Basic reproduction number Human infections with SARS-CoV-2 were first reported in late 2019, the syndrome was named Coronavirus-Disease-19 (COVID- 19). Infections spread rapidly worldwide, in March 2020 WHO declared COVID as a new pandemic.…”

“…The rate of infected health care personnel in all cases was 2.7% in China, 11% in Italy and 5.8% in Germany [2,4,18]. In seroepidemiologic studies from Italy and Spain the seroprevalence of SARS-CoV-2 infection was approximately twice the rate of workers in other occupations (Italy 5.3% vs. 2.8%, Spain 10.2% vs. 4.8%, UK 11.7% vs. 5.3%) [19][20][21]. Fortunately, the number and rate of severe cases and complications in contrast are low in this group [2,4,18].…”

“…Investigators from the Imperial College, London, have first established a mathematical model to estimate age dependent case-and infection fatality rates from a high number of cases (Table 2). Other estimates have been based on related models, cohort studies, on national seroprevalence studies and outbreaks, which have probably been monitored almost completely, e.g., South Korea (Table 2) [17,19,24,27,28].…”

“…National or regional attack rates can be measured by seroprevalence studies or estimated using IFR models (Table 3). Seroprevalence studies from different nations differ widely, with additional variation between regions (Table 3) [19,33,34,12,20,21].…”