5.6% seroprevalence of SARS-CoV-2 antibodies in England during the second wave

A recent study conducted as part of the Real-Time Assessment of Community Transmission-2 (REACT-2) program estimated the seroprevalence of anti-coronavirus 2 (SARS-CoV-2) antibodies in severe acute respiratory syndrome among adult populations in England. .

Research reveals a seroprevalence of 5.6% at the start of the second wave of the 2019 coronavirus disease (COVID-19) pandemic. The study is currently available on the medRxiv * preprint server pending peer review.

context

SARS-CoV-2 antibody seroprevalence surveys are carried out to estimate the proportion of individuals in a population who have already been infected with SARS-CoV-2 and have subsequently developed antibodies against the virus. Several factors can influence the seroprevalence of a population, including infection rate, vaccination rate, and declining antibody levels in people previously infected.

In England, the devastating first wave of COVID-19 caused significant morbidity and mortality in March and April 2020.

Strict implementation of control measures subsequently resulted in a sustained reduction in infection and death rates until the emergence of the second wave in late August.

As part of the REACT-2 program, the first round of seroprevalence surveys estimated that the prevalence of anti-SARS-CoV-2 antibodies in the adult population of England was 6% in June and July 2020. By Subsequently, the two other rounds of the study conducted in August and September 2020 estimated the seroprevalence at 4.4%, indicating a decrease in the level of antibodies in the population.

In the current cycle 4 study, scientists estimated the seroprevalence of SARS-CoV-2 antibodies in the population of England in October and November 2020.

Study design

Initially, the scientists selected a random sample from the adult population and provided them with a lateral flow immunoassay kit to perform antibody tests at home. The test estimated antibody levels against the S1 subunit of SARS-CoV-2 using blood samples taken by finger prick.

Additionally, they constructed epidemic curves using data obtained from participants in all cycles who had a positive antibody test result and reported a confirmed or suspected case of COVID-19.

Important observations

161,537 people aged 18 or over participated in the survey between October 27 and November 10, 2020.

Based on the results of self-administered tests, the seroprevalence of SARS-CoV-2 antibodies was estimated to be 5.6%. This indicates a relative increase of 27% compared to 4.4% in the Cycle 3 study.

The epidemic curves constructed from all the cycles revealed that the majority of cases were from the first wave of the pandemic in March and April 2020. In addition, the curves highlighted the start of the second wave in early September 2020. .

The greatest increase in seroprevalence was observed in the 18-24 age group, with an overall increase from 6.7% in round 3 to 9.9% in round 4. In students, the increase was 5.9% in round 3 to 12.1% in round 4. Based on geographic locations, the greatest increase in seroprevalence was observed in Yorkshire and the Humber (from 3.4% to 6, 3%) and in the Northwest (from 4.5% to 7.7%). In these areas, the prevalence was relatively higher in some lower level local communities.

In contrast, no change in prevalence (9.5%) between cycles 3 and 4 was observed in London. Likewise, a stable prevalence was observed among blacks, healthcare workers and nursing home workers. Regarding ethnic variation, the highest seroprevalence was observed among people from Bangladesh (15.1%), Pakistan (13.9%) and Africa (13.5%). The lowest seroprevalence was observed among people of white British ethnicity.

Further statistical analysis identified an inverse correlation of seroprevalence with household income and households with children.

Importance of the study

The study shows that during the first phase of the second wave in England, there was an increase in the prevalence of SARS-CoV-2 antibodies compared to that at the end of the first wave.

In general, the greatest increase in the prevalence of antibodies was observed among young people, including students.

Overall, the study highlights that a significant proportion of people in England remain susceptible to infection with SARS-CoV-2 even during the second wave of the COVID-19 pandemic.

*Important Notice

medRxiv publishes preliminary scientific reports which are not peer reviewed and, therefore, should not be considered conclusive, guide clinical practice / health-related behavior, or treated as established information.