A recent study conducted as a part of the Real-Time Assessment of Community Transmission-2 (REACT-2) program has estimated the seroprevalence of anti-severe acute respiratory syndrome coronavirus 2 (SARS-CoV-2) antibodies among adult populations in England.
The research reveals 5.6% seroprevalence during the early second wave of the coronavirus disease 2019 (COVID-19) pandemic. The study is currently available on the medRxiv* preprint server while it awaits peer review.
Seroprevalence surveys of SARS-CoV-2 antibodies are conducted to estimate the proportion of individuals in a population who have previously been infected with SARS-CoV-2 and subsequently have developed antibodies against the virus. Several factors can influence the seroprevalence of a population, including the rate of infection, rate of vaccination, and declining antibody levels in previously infected individuals.
In England, the devastating first wave of COVID-19 has caused significant morbidity and mortality in March and April 2020.
Strict implementation of control measures subsequently caused a sustained reduction in infection and mortality rates until the emergence of the second wave in late August.
Under 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 at 6% during June and July 2020. Subsequently, the other two rounds of the study conducted in August and September 2020 have estimated 4.4% seroprevalence, indicating a declining antibody level in the population.
In the current round 4 study, the scientists have estimated the seroprevalence of SARS-CoV-2 antibodies in the population of England during October and November 2020.
Initially, the scientists selected a random sample of the adult population and provided them with a lateral flow immunoassay kit to perform antibody testing at home. The assay estimated the levels of antibodies against the S1 subunit of SARS-CoV-2 using finger-prick blood samples.
Moreover, they constructed epidemic curves using the data obtained from participants from all rounds who had a positive antibody test result and reported a confirmed or suspected case of COVID-19.
161,537 individuals aged 18 years or above participated in the survey between October 27 and November 10, 2020.
Based on the self-administered test results, the seroprevalence of SARS-CoV-2 antibodies was estimated to be 5.6%. This indicates a relative increase of 27% from 4.4% in the round 3 study.
The epidemic curves constructed from all rounds revealed that the majority of cases were from the first wave of the pandemic in March and April 2020. Moreover, the curves highlighted the beginning of the second wave in early September 2020.
The highest increase in seroprevalence was observed in the age group of 18 – 24 years, with an overall increase from 6.7% in round 3 to 9.9% in round 4. Among students, the increase was from 5.9% in round 3 to 12.1% in round 4. Based on geographical locations, the highest increase in seroprevalence was observed in Yorkshire and The Humber (from 3.4% to 6.3%) and the North West (from 4.5% to 7.7%). In these regions, the prevalence was relatively higher in some lower-tier local authority areas.
In contrast, no change in prevalence (9.5%) between rounds 3 and 4 was observed in London. Similarly, a stable prevalence was observed among Black people, healthcare workers, and care home workers. Regarding ethnic variation, the highest seroprevalence was observed in people from Bangladesh (15.1%), Pakistan (13.9%), and Africa (13.5%). The lowest seroprevalence was observed in people of White British ethnicity.
Further statistical analysis identified an inverse correlation of seroprevalence with household income and households with children.
The study demonstrates that during the early phase of the second wave in England, there was an increase in SARS-CoV-2 antibody prevalence compared to that at the end of the first wave.
In general, the highest increase in antibody prevalence has been observed in younger people, including students.
Overall, the study highlights that a significant proportion of people in England remain susceptible to SARS-CoV-2 infection even during the second wave of the COVID-19 pandemic.
medRxiv publishes preliminary scientific reports that are not peer-reviewed and, therefore, should not be regarded as conclusive, guide clinical practice/health-related behavior, or treated as established information.