REACT-2 Round 5: increasing prevalence of SARS-CoV-2 antibodies demonstrate impact of the second wave and of vaccine roll-out in England (preprint)

Abstract Background England has experienced high rates of SARS-CoV-2 infection during the COVID-19 pandemic, affecting in particular minority ethnic groups and more deprived communities. A vaccination programme began in England in December 2020, with priority given to administering the first dose to the largest number of older individuals, healthcare and care home workers. Methods A cross-sectional community survey in England undertaken between 26 January and 8 February 2021 as the fifth round of the REal-time Assessment of Community Transmission-2 (REACT-2) programme. Participants completed questionnaires, including demographic details and clinical and COVID-19 vaccination histories, and self-administered a lateral flow immunoassay (LFIA) test to detect IgG against SARS-CoV-2 spike protein. There were sufficient numbers of participants to analyse antibody positivity after 21 days from vaccination with the PfizerBioNTech but not the AstraZeneca/Oxford vaccine which was introduced slightly later. Results The survey comprised 172,099 people, with valid IgG antibody results from 155,172. The overall prevalence of antibodies (weighted to be representative of the population of England and adjusted for test sensitivity and specificity) in England was 13.9% (95% CI 13.7, 14.1) overall, 37.9% (37.2, 38.7) in vaccinated and 9.8% (9.6, 10.0) in unvaccinated people. The prevalence of antibodies (weighted) in unvaccinated people was highest in London at 16.9% (16.3, 17.5), and higher in people of Black (22.4%, 20.8, 24.1) and Asian (20.0%, 19.0, 21.0) ethnicity compared to white (8.5%, 8.3, 8.7) people. The uptake of vaccination by age was highest in those aged 80 years or older (93.5%). Vaccine confidence was high with 92.0% (91.9, 92.1) of people saying that they had accepted or intended to accept the offer. Vaccine confidence varied by age and ethnicity, with lower confidence in young people and those of Black ethnicity. Particular concerns were identified around pregnancy, fertility and allergies. In 971 individuals who received two doses of the Pfizer-BioNTech vaccine, the proportion testing positive was high across all age groups. Following a single dose of Pfizer-BioNTech vaccine after 21 days or more, 84.1% (82.2, 85.9) of people under 60 years tested positive (unadjusted) with a decreasing trend with increasing age, but high responses to a single dose in those with confirmed or suspected prior COVID at 90.1% (87.2, 92.4) across all age groups. Conclusions There is uneven distribution of SARS-CoV-2 antibodies in the population with a higher burden in key workers and some minority ethnic groups, similar to the pattern in the first wave. Confidence in the vaccine programme is high overall although it was lower in some of the higher prevalence groups which suggests the need for improved communication about specific perceived risks. Two doses of Pfizer-BioNTech vaccine, or a single dose following previous infection, confers high levels of antibody positivity across all ages. Further work is needed to understand the relationship between antibody positivity, clinical outcomes such as hospitalisation, and transmission.

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

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.

Public perceptions and preventive behaviours during the early phase of the COVID-19 pandemic: a comparative study between Hong Kong and the United Kingdom (preprint)

BackgroundIn the absence of treatments and vaccines, the mitigation of COVID-19 relies on population engagement in non-pharmaceutical interventions, which is driven by their risk perception, anxiety level and knowledge. There may also be regional discrepancies in these drivers due to different historical exposure to disease outbreaks, government responses and cultures. As such, this study compared psycho-behavioral responses in two regions during the early phase of the pandemic. MethodsComparable cross-sectional surveys were administered among adults in Hong Kong (HK) and the United Kingdom (UK) during the early phase of each respective epidemic. Explanatory variables included demographics, risk perception and knowledge of COVID-19, anxiety level and preventive behaviors. Responses were weighted according to census data. Logistic regression models, including interaction terms to quantify regional differences, were used to assess the association between explanatory variables and the adoption of social-distancing measures. ResultsData of 3431 complete responses (HK:1663; UK:1768) were analysed. Perceived severity differed by region (HK: 97.5%; UK: 20.7%). A large proportion of respondents were abnormally/borderline anxious (HK:64.8%; UK:45.9%) and regarded direct contact with infected individuals as the transmission route of COVID-19 (HK:94.0-98.5%; UK:69.2-93.5%), with HK identifying additional routes. HK reported high levels of adoption of social-distancing (HK:32.4-93.7%; UK:17.6-59.0%) and mask-wearing (HK:98.8%; UK:3.1%). The impact of perceived severity and perceived ease of transmission on the adoption of social-distancing varied by region. In HK, they had no impact, whereas in the UK, those who perceived severity as "high" were more likely to adopt social-distancing (aOR:1.58-3.01), and those who perceived transmission as "easy" were prone to both general social-distancing (aOR:2.00, 95% CI:1.57, 2.55) and contact avoidance (aOR:1.80, 95% CI: 1.41, 2.30). The impact of anxiety on adopting social-distancing did not vary by region. DiscussionThese results suggest that health officials should ascertain and consider baseline levels of risk perception and knowledge in the populations, as well as prior sensitisation to infectious disease outbreaks, during the development of mitigation strategies. Risk communication should be done through suitable media channels - and trust should be maintained - while early intervention remains the cornerstone of effective outbreak response.

Perceptions and behavioural responses of the general public during the COVID-19 pandemic: A cross-sectional survey of UK Adults (preprint)

ObjectiveTo examine risk perceptions and behavioural responses of the UK adult population during the early phase of the COVID-19 epidemic in the UK. DesignA cross-sectional survey SettingConducted with a nationally representative sample of UK adults within 48 hours of the UK Government advising the public to stop non-essential contact with others and all unnecessary travel. Participants2,108 adults living in the UK aged 18 years and over. Data were collected between March 17 and 18 2020. Main outcome measuresDescriptive statistics for all survey questions, including the number of respondents and the weighted percentages. Logistic regression was used to identify sociodemographic variation in: (1) adoption of social-distancing measures, (2) ability to work from home, and (3) willingness and (4) ability to self-isolate. ResultsOverall, 1,992 (94.2%) respondents reported taking at least one preventive measure: 85.8% washed their hands with soap more frequently; 56.5% avoided crowded areas and 54.5% avoided social events. Adoption of social-distancing measures was higher in those aged over 70 compared to younger adults aged 18 to 34 years (aOR:1.9; 95% CI:1.1 to 3.4). Those with the lowest household income were six times less likely to be able to work from home (aOR:0.16; 95% CI:0.09 to 0.26) and three times less likely to be able to self-isolate (aOR:0.31; 95% CI:0.16 to 0.58). Ability to self-isolate was also lower in black and minority ethnic groups (aOR:0.47; 95% CI:0.27 to 0.82). Willingness to self-isolate was high across all respondents. ConclusionsThe ability to adopt and comply with certain NPIs is lower in the most economically disadvantaged in society. Governments must implement appropriate social and economic policies to mitigate this. By incorporating these differences in NPIs among socio-economic subpopulations into mathematical models of COVID-19 transmission dynamics, our modelling of epidemic outcomes and response to COVID-19 can be improved.