Resurgence of Covid-19 in Manaus, Brazil, despite high seroprevalence

‘A study published in The Lancet analyzed the increased SARS-CoV-2 transmission in Manaus, Brazil, a region that had previously shown high levels of seroprevalence among its community members. A study conducted in October 2020 detected SARS-CoV-2 antibodies in samples from 76% of blood donors, which suggested that the region may have reached the threshold to provide some level of community immunity (ie, herd immunity). Despite the high seroprevalence, Manaus exhibited a large surge in COVID-19 cases and hospitalizations in January 2021.

‘The researchers present 4 possible explanations for the surprising surge in cases. First, the previous study could have overestimated the seroprevalence, which could have put the community below the herd immunity threshold. Second, immunity to SARS-CoV-2 conferred by earlier infection could have waned, resulting in re-infections. Third, the new infectious could be a result of emerging variants, including the P.1 variant first reported in the area, that are less susceptible to antibodies from prior infections. And finally, new SARS-CoV-2 lineages could simply be exhibiting much higher transmissibility, which could allow widespread community transmission even in areas with high existing seroprevalence. The researchers note that these theories are not mutually exclusive, and further study is needed to better characterize the factors driving the current resurgence. In particular, it is critical to investigate the potential that emerging variants could evade antibodies developed from infection with other strains, which could inform response activities in communities around the world.’ 

Read here (The Lancet, Jan 27, 2021)

Seroprevalence study estimates 6% of Britain's population infected, higher among ethnic minorities and healthcare workers

‘Researchers at Imperial College London reported findings from a large seroprevalence study involving more than 100,000 participants in the UK... It estimates the overall UK seroprevalence to be 6.0%, which translates to approximately 3.36 million adult infections through June 20. For comparison, the UK has reported 313,798 cumulative cases to date, which corresponds to approximately 0.6% of the total UK adult population.’ -- John Hopkins e-newsletter.

‘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.’ Conclusion of the study.

Download here (Imperial College Institute of Global Health Innovation, August 2020)

What Covid-19 antibody tests can and cannot tell us

‘Dozens of antibody tests for the novel coronavirus have become available in recent weeks. And early results from studies of such serological assays in the U.S. and around the world have swept headlines. Despite optimism about these tests possibly becoming the key to a return to normal life, experts say the reality is complicated and depends on how results are used.

‘Antibody tests could help scientists understand the extent of COVID-19’s spread in populations. Because of limitations in testing accuracy and a plethora of unknowns about immunity itself, however, they are less informative about an individual’s past exposure or protection against future infection.’

Read here (Scientific American, May 5, 2020)

Roche's serology test with ‘specificity greater than 99.8% and sensitivity of 100%’ gets FDA approval

‘Roche intends to provide tens of millions of tests worldwide by the end of May, and the company is working to expand production capacity. The Roche test requires a blood draw instead of a finger prick. The test takes approximately 18 minutes to run and is fully automated, and the testing system can perform as many as 300 tests per hour.’

Read here (Roche press release, May 3, 2020)

The results of coronavirus ‘serosurveys’ are starting to be released. Here’s how to kick their tires

‘Results from the first studies designed to determine how widely the coronavirus has spread in communities have started to trickle in, drawing immense attention. These studies, after all, are seen as critical indicators of when it might be safe to lift movement restrictions.

‘Already, though, experts are raising concerns about the validity of some of the studies and cautioning officials and the general public not to put too much weight on any one finding.

‘Known as serological surveys, the studies involve testing the blood of people not diagnosed with Covid-19 to determine whether they had previously been infected by the SARS-CoV-2 virus. They are important because they can flesh out the picture of how many people in any given community may have had Covid-19, even if they were unaware they were infected.‘

Read here (STAT News, April 24, 2020)

Download here Q&A from The Wadsworth Center (WC), the public health laboratory of the New York State Department of Health (NYSDOH)

Developing a National Strategy for Serology (antibody testing) in the United States: Publication by John Hopkins

‘Serology tests will be an important tool for public health workers to estimate the prevalence of disease. These tests will be in high demand by individuals who hope to assess their risks of immunity to SARS-CoV-2. Serology testing, among other nonpharmaceutical interventions, can help to bridge the time before a vaccine is available. However, validated, accurate tests are currently in short supply. In this report, we seek to draw attention to the options for expanding access so that the potential benefits of serology tests can be realised as soon as practicable.’

Download here (John Hopkins Center for Health and Security, April 22, 2020)