Community prevalence of SARS-CoV-2 in England from April to November, 2020: results from the ONS Coronavirus Infection Survey

Abstract

Background Decisions about the continued need for control measures to contain the spread of severe acute respiratory syndrome coronavirus 2 (SARS-CoV-2) rely on accurate and up-to-date information about the number of people testing positive for SARS-CoV-2 and risk factors for testing positive. Existing surveillance systems are generally not based on population samples and are not longitudinal in design. Methods Samples were collected from individuals aged 2 years and older living in private households in England that were randomly selected from address lists and previous Office for National Statistics surveys in repeated crosssectional household surveys with additional serial sampling and longitudinal follow-up. Participants completed a questionnaire and did nose and throat self-swabs. The percentage of individuals testing positive for SARS-CoV-2 RNA was estimated over time by use of dynamic multilevel regression and poststratification, to account for potential residual non-representativeness. Potential changes in risk factors for testing positive over time were also assessed. The study is registered with the ISRCTN Registry, ISRCTN21086382. Findings Between April 26 and Nov 1, 2020, results were available from 1 191 170 samples from 280 327 individuals; 5231 samples were positive overall, from 3923 individuals. The percentage of people testing positive for SARS-CoV-2 changed substantially over time, with an initial decrease between April 26 and June 28, 2020, from 0•40% (95% credible interval 0•29-0•54) to 0•06% (0•04-0•07), followed by low levels during July and August, 2020, before substantial increases at the end of August, 2020, with percentages testing positive above 1% from the end of October, 2020. Having a patientfacing role and working outside your home were important risk factors for testing positive for SARS-CoV-2 at the end of the first wave (April 26 to June 28, 2020), but not in the second wave (from the end of August to Nov 1, 2020). Age (young adults, particularly those aged 17-24 years) was an important initial driver of increased positivity rates in the second wave. For example, the estimated percentage of individuals testing positive was more than six times higher in those aged 17-24 years than in those aged 70 years or older at the end of September, 2020. A substantial proportion of infections were in individuals not reporting symptoms around their positive test (45-68%, dependent on calendar time.Interpretation Important risk factors for testing positive for SARS-CoV-2 varied substantially between the part of the first wave that was captured by the study (April to June, 2020) and the first part of the second wave of increased positivity rates (end of August to Nov 1, 2020), 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 COVID-19 pandemic moving forwards.

The success of SARS-CoV-2 vaccines and challenges ahead

“…For some vaccines, VOC-specific VE data are available because the VOCs emerged while phase 3 trials were being conducted and viral samples from trial participants in both the vaccine and placebo arms (Sadoff et al, 2021;Shinde et al, 2021), were sequenced. In addition, observational data from countries experiencing the widespread circulation of VOCs have also provided an estimate of VE against the variants, although these data are less precise than those obtained from phase 3 trials (Abu-Raddad et al, 2021;Dagan et al, 2021;Lumley et al, 2021;Pouwels et al, 2021;Pritchard et al, 2021;Vasileiou et al, 2021). There is also emerging evidence that current vaccines can prevent the rapid rise of some VOCs (Munitz et al, 2021) and reduce the risk of onward transmission in families (https://khub.net/ documents/135939561/390853656/Impact+of+vaccination+on +household+transmission+of+SARS-COV-2+in+England.pdf/ 35bf4bb1-6ade-d3eb-a39e-9c9b25a8122a?t=16195515712 14).…”

Impacts of the Covid‐19 pandemic on the health of university students

“…Although it Is not proven that the increases in Covid-19 cases in adjacent areas were initiated by infected students, there is now more convincing evidence that increased attack rates in the 18-24-year old age category did lead to a resurgence of the pandemic more generally in the UK between September and November 2020. 46 Hence, although serious illness did not commonly feature in the Covid-19 outbreaks that occurred on campuses at the beginning of the academic year, there was nevertheless serious and prolonged disruption to the student experience. Part of the rationale for reopening campuses was to facilitate limited social activities for a more enriching student experience, however, the numerous Covid-19 outbreaks in residential settings ended up achieving the opposite in many instances.…”

Impact of vaccination on new SARS-CoV-2 infections in the UK

“…The Office for National Statistics (ONS) COVID-19 Infection Survey (CIS) is a large household survey with longitudinal follow-up (ISRCTN21086382, https://www.ndm.ox.ac.uk/covid-19/covid-19infection-survey/protocol-and-information-sheets) (details in 18 ). Private households are randomly selected on a continuous basis from address lists and previous surveys to provide a representative sample across the UK.…”

“…Samples are called positive if either N or ORF1ab, or both, are detected. The S gene alone is not considered a reliable positive 18 , but could accompany other genes (ie, one, two, or three gene positives).…”