How serology samples are used by PHE to monitor COVID-19 immunity
A number of serological collections have been established by PHE to provide an age-stratified geographically representative sample across England over time. These include samples from healthy adult blood donors attending for routine blood tests in primary care through RCGP RSC practices.
These samples are currently being tested using the Euroimmun IgG assay to determine the proportion of the population with detectable antibodies to SARS CoV-2.
Week 31 serology update:
Overall population weighted prevalence among blood donors aged 17 years and older in England was 5.8% (95% CI 5.3% - 6.3%) (unadjusted) or 6.1% (95% CrI 5.5% - 6.7%) after adjustment for the accuracy of the Euroimmun assay (sensitivity 83.0% and specificity 99.3%) for the period 22nd June – 20th July (weeks 26-30). Estimates are based on 9220 samples, of which 565 were positive. The latest data includes donors aged 70 years and older who were previously excluded from donating during lockdown.