This finding is corroborated by seroprevalence data from other Western countries in similar phases of the pandemic: a study of blood donors/pregnant women in Stockholm, Sweden, showed approximately 15% seroprevalence by mid-December 2020 (this is comparable with our estimates from urban areas such as Greater Glasgow, which approached 13% by the end of December)

This finding is corroborated by seroprevalence data from other Western countries in similar phases of the pandemic: a study of blood donors/pregnant women in Stockholm, Sweden, showed approximately 15% seroprevalence by mid-December 2020 (this is comparable with our estimates from urban areas such as Greater Glasgow, which approached 13% by the end of December).8A household survey from Geneva found a slightly higher seroprevalence rate of 21%.9 Seroprevalence may, however, underestimate true population exposure for several reasons: lack of antibody persistence7and the role of other immune responses in neutralizing contamination (there is evidence that some individuals who are exposed to SARS-CoV-2 do not develop measurable antibodies, suggesting the role of cellular immunity).10The Rabbit polyclonal to ARHGAP20 ability of binding antibodies to confer immunity to SARS-CoV-2 infection is also not known, and antibody neutralisation activity may be less among asymptomatic individuals.11 Limitations of LY2452473 our study include the uncertainty in the sensitivity and specificity of the assays and uncertainty with regard to the representativeness of our samples with regard to the general Scottish population. rates were 0% until the end of March, when LY2452473 they increased contemporaneously with the first pandemic wave. Seroprevalence rates remained stable through the summer (range: 3%5%) during a period of social restrictions, after which they increased concurrently with the second wave, reaching 9.6% (95% confidence interval [CI]: 8.4%10.8%) in the week beginning 28th December in 2020. Seroprevalence rates were lower in rural vs. urban areas (adjusted odds ratio [AOR]: 0.70, 95% CI: 0.610.79) and among individuals aged 2039 years and 60 years and older (AOR: 0.74, 95% CI: 0.640.86; AOR: 0.80, 95% CI: 0.690.91, respectively) relative to those aged 019 years. == Conclusions == After two waves of the COVID-19 pandemic, less than one in ten individuals in the Scottish population had antibodies to SARS-CoV-2. Seroprevalence may underestimate the true population exposure as a result of waning antibodies among individuals who were infected early in the first wave. Keywords:SARS-CoV-2, COVID-19, Seroprevalence, Antibodies, Cross sectional The first severe acute respiratory syndrome coronavirus 2 (SARS-CoV-2) contamination in Scotland was reported on 1 March 2020. The country has since experienced two waves of COVID-19 (the disease associated with SARS-CoV-2), which has resulted in one of the highest excess mortality rates worldwide. Estimates of the proportion of individuals in the population who have been exposed to SARS-CoV-2 both symptomatic and asymptomatic are necessary to understand the progression of the pandemic to date. Because polymerase chain reaction (PCR) testing in the general population until recently has mainly been limited to those with symptoms, seroprevalence studies, which measure antibodies to SARS-CoV-2, provide a means of measuring population exposure. Furthermore, it is essential to have estimates of the extent of exposure from wild-type contamination before rollout of vaccination. Most population-based seroprevalence surveys to date have focused on short time frames or subnational populations; here, we examine serial cross-sectional estimates of seroprevalence over a 12-month period in the Scottish general population, using residual blood samples from different sources. Residual blood samples, originally collected for other purposes, were obtained from primary care (i.e. general practice) and antenatal care settings. Antenatal samples were retrospectively identified at regional laboratories across Scotland that store specimens taken for infectious disease screening at week 12 of pregnancy; these specimens are submitted from all antenatal settings in the regional health authority areas (National Health Support (NHS) Boards) that are covered by these laboratories. Samples were available from International Organization for Standardization (ISO) week 1 (week beginning [w/b] 30th December 2019) to ISO week 26 (w/b 29th June 2020); all available samples with sufficient volume were included (totalling 16,157). Primary care samples were retrieved from regional laboratories, which receive samples from general practices across the NHS Boards that they cover. Approximately, 700 weekly samples were obtained between ISO week 17 (w/b 20th April 2020) and ISO week 53 (w/b 28th December 2020), totalling 25,320 samples. Primary care samples were selected according to an age/sex/NHS Board sampling frame corresponding to the Scottish general population structure. Eleven and seven of the 14 NHS boards in Scotland participated in LY2452473 the primary care and antenatal surveillance, covering 91% and 73% of the Scottish population, respectively. This analysis was restricted to samples up until the end of December 2020 to measure exposure to wild-type infection and not vaccine response: vaccination rollout for target groups began in Scotland on 8th December 2020; however, given the lag time between exposure to vaccination and seroconversion,1,2antibodies resulting from vaccine response would likely not be detectable in seroprevalence estimates until early January 2021. Samples were anonymised before testing: only age (and sex for primary care samples) and the NHS Board were attached to the result. Primary care samples were sent to the Scottish Microbiology Reference Laboratory, where they were.