Community prevalence of SARS-CoV-2 in England during April to September 2020: Results from the ONS Coronavirus Infection Survey

Abstract

Background: Decisions regarding the continued need for control measures to contain the spread of SARS-CoV-2 rely on accurate and up-to-date information about the number of people and risk factors for testing positive. Existing surveillance systems are not based on population samples and are generally not longitudinal in design. Methods: From 26 April to 19 September2020, 514,794 samples from 123,497 individuals were collected from individuals aged 2 years and over from a representative sample of private households from England. Participants completed a questionnaire and nose and throat swab were taken. The percentage of individuals testing positive for SARS-CoV-2 RNA was estimated over time using dynamic multilevel regression and post-stratification, to account for potential residual non-representativeness. Potential changes in risk factors for testing positive over time were also evaluated using multilevel regression models. Findings: Between 26 April and 19 September 2020, in total, results were available from 514,794 samples from 123,497 individuals, of which 489 were positive overall from 398 individuals. The percentage of people testing positive for SARS-CoV-2 changed substantially over time, with an initial decrease between end of April and June, followed by low levels during the summer, before marked increases end of August and September 2020. Having a patient-facing role and working outside your home were important risk factors for testing positive in the first period but not (yet) in the second period of increased positivity rates, and age (young adults) being an important driver of the second period of increased positivity rates. A substantial proportion of infections were in individuals not reporting symptoms (53%-70%, dependent on calendar time). Interpretation: Important risk factors for testing positive varied substantially between the initial and second periods of higher positivity rates, and a substantial proportion of infections were in individuals not reporting symptoms, indicating that continued monitoring for SARS-CoV-2 in the community will be important for managing the epidemic moving forwards.

Ct threshold values, a proxy for viral load in community SARS-CoV-2 cases, demonstrate wide variation across populations and over time

“…This has recently also been proposed on the basis of theoretical work linking effective reproduction numbers to population level Ct[26]. For example, declines in mean and median Ct values were apparent throughout August ( Figure 1B ), although positivity rates in the survey were only noted to increase in early September[9]. Ct data are widely available within laboratory management systems and could be used alongside available risk factor and symptom information to facilitate more informed and effective individual-level and public health responses to the SARS-CoV-2 pandemic.…”

“…However, number of genes detected and symptoms are both potential mediators of effects of demographic factors ( Supplementary Figure 2 ); and there were strong effects of calendar time on positivity in different demographic subgroups[9] and on Ct values ( Figure 1A ). Excluding the potential mediators (number of genes detected, symptoms) and adjusting for visit date, Ct values remained independently lower (i.e.…”

The duration, dynamics and determinants of SARS-CoV-2 antibody responses in individual healthcare workers

“…Our findings contrast with the repeated cross-sectional REACT2 study,[23] which reported greater reductions over time at a population-level in the proportion of adults ≥65 years testing antibody-positive, and more sustained responses in those 18-24 years. Nearly all HCWs in our study were <65 years, other differences may arise from study design, the assay used, and the potential for new infections predominantly in younger people[24] to replace others who had sero-reverted, supporting population-level seroprevalence (in our study these individuals are followed separately). Ongoing longitudinal studies are required to determine the long-term kinetics of antibody-mediated response to SARS-CoV-2, and responses to re-exposure.…”

Detecting COVID-19 infection hotspots in England using large-scale self-reported data from a mobile application: a prospective, observational study

“…We used three datasets to validate our models: the Office for National Statistics (ONS) Community Infection Survey, the Real-time Assessment of Community Transmission (REACT-1) study, and UK Government testing data. The ONS survey 7 is a longitudinal survey of individuals selected to be a representative sample of private households (excluding eg, care homes and student accommodation), which began on April 26, 2020. Individuals in the ONS survey are supervised while they self-administer nose and throat swabs.…”