Rapid increase in level of seropositivity

The most recent data released from the Coronavrius (COVID-19) Infection Survey up to 14 March (based on blood samples taken from home visits) indicates a range of seropositivity levels from 54.7% in England to 42.6% in Scotland.

Figure 3.1 sets out the seropositivity levels for different age groups in each country, with the highest rates in the age group 70-74. These levels will be driven by prior infections and vaccinations, and hence relate to the current stage in the vaccination roll-out programme recommended by the JCVI.

Figure 3.1 - Seropositivity by age in UK countries

Source:COVID-19 Infection Survey

FIgure 3.2 provides further analysis of differences in seropositivity between English regions, highest in the North West at 60.0% and lowest in the South East at 50.3%.

Figure 3.2 - Seropositivity by different English regions

Source:COVID-19 Infection Survey

Earlier studies of seropositivity in 2020 showed London as the highest region, but London is also the English region where the estimated prevalence of those receiving vaccination is lowest at 50.1% (vs 59.4% in the West Midlands).

Whilst the UK has some of the most comprehensive studies of seropositivity, there are many different studies that are ongoing at national, regional and local levels. As first reported in the Lancet in August 2020, Serotracker represents the extra-ordinary efforts of a group of medical and doctoral students that have screened thousands of publications to produce a systematically reviewed map & database of serology testing around the world.

As at 1 April, Serotracker provides data across 79 countries, based on 1,025 serology studies and almost 12 million antibody tests.