UK Antibodies Prevalence Study Suggests that Minorities Contract COVID-19 at Disproportionately Higher Rates

Many have suggested that minority populations have suffered adverse effects from COVID-19 disproportionate numbers. An August study from the United Kingdom provides powerful evidence to support this theory based on SARS-CoV-2 antibody prevalence. Here is the low down.

The Diagnostic Challenge

England experienced a particularly large outbreak of SARS-CoV-2 infection. The country’s first COVID-19 death occurred on Feb. 28. By June, England had the highest excess mortality in Europe by June, with in-hospital deaths peaking at 800 per day within six weeks. Hospital admission and mortality data showed that the highest rates of deaths were in older people including those living in long-term care, and in people of minority ethnic groups, particularly Black and Asian (mainly South Asian) individuals.

Was there any scientific evidence to support these demographic patterns? That is the question the researchers set out to answer, focusing on antibody data which provides a measure of SARS-CoV-2 exposure. Most infected people mount an IgG antibody response detectable after 14 to 21 days after exposure, although levels may start to wane after approximately 90 days. The study authors hoped to use antibody prevalence data from a large community-based evaluation based on unsupervised use of lateral flow immunochromatographic assay (LFIA) tests at home of people in England up to July 2020. Specifically, their goals were to:

• Estimate the cumulative community seroprevalence of IgG antibodies for SARSCoV-2;
• Identify those at most risk of infection; and
• Estimate the total number of infected individuals in England and the infection fatality ratio (IFR).

How the Study Was Conducted

The testing was carried out as part of the government-funded National Real-time Assessment of Community Transmission-2 (REACT-2) seroprevalence study and led by investigators at the Imperial College London. Personalized invitations were sent to 315,000 individuals aged 18 years and over. The 121,000 participants who signed up registered via an online portal or by telephone.

The registered participants received a test kit by mail that contained a self-administered point-of-care LFIA test and instructions with links to an online video. Participants also completed a short registration questionnaire online or via phone and a further survey upon completion of their self-test providing information on demographics, household composition, recent symptoms and a photo of the result.

Between June 20 and July 13, the volunteers tested themselves at home to determine if they had developed antibodies against the SARS-CoV-2 virus that causes COVID-19 using a finger prick lateral flow immunoassay manufactured by Fortress Diagnostics, an in vitro diagnostics manufacturer based in Antrim, Northern Ireland.

Findings: Ethnicity Does Matter

Of the 121,976 people who were sent LFIA test kits, 109,076 (89.4 percent) completed the questionnaire, of whom 105,651 also completed the test; 5,743 (5.4 percent) reported an invalid or unreadable result, leaving 99,908 (94.6 percent) individuals. Of these, 5,544 tested IgG positive and 94,364 IgG negative, giving a crude prevalence of 5.6 percent.

After adjusting for the performance characteristics of the test and re-weighting, the authors estimated that overall prevalence for England was 6.0 percent during the period from June 20 to July 13, 2020. This equates to 3.36 million adults in England who had been infected with SARS-CoV-2 in England.

Prevalence was highest for people ages 18 to 24 years and in London. While 7.9 percent of those age 18 to 34 had antibodies, just 3.3 percent of those over age 75 did. Antibody prevalence among Londoners was 13.0 percent, as compared to under 3 percent in the less populated southwestern areas of the country.

By ethnic group, the highest prevalence was found in people of Black (including Black Caribbean, African and Black British) (17.3 percent) and Asian (mainly South Asian) ethnicities (11.9 percent). In comparison, prevalence was only 5.0 percent in people of White ethnicity. Poorer people were also more likely to have antibody exposure than wealthier people.

Not surprisingly, the researchers also found higher prevalence among workers in nursing homes (16.5 percent found to have IgG antibodies) and other healthcare workers (11.7 percent). were more likely to have antibodies, compared to those who were not, with 16.5% of nursing home workers and 11.7% of healthcare workers showing antibodies.

Reinforcing curious findings from earlier studies, the researchers found that current smokers have a lower prevalence of SARS-CoV-2 infection than non-smokers, 3.2 percent versus 5.2 percent.

Takeaway

The study authors believe that this is the largest community-based evaluation of antibody prevalence, and the only nationwide study based on unsupervised use of LFIA tests at home. And it suggests that ethnicity is, in fact, a factor in susceptibility to infection and that members of minority populations contract the virus at significantly higher rates than persons of White ethnicity. The UK government plans to conduct a follow-up antibodies prevalence study on 200,000 in the fall.