July 7, 2020

expert reaction to study looking at the prevalence of SARS-CoV-2 in Spain

A study, published in The Lancet, looked at the prevalence of the SARS-CoV-2 virus in Spain.

Prof Eleanor Riley, Professor of Immunology and Infectious Disease, University of Edinburgh, said:

“The low prevalence of antibodies in a country such as Spain, which was hit relatively hard by the pandemic, is somewhat surprising and suggests that exposure to the virus has been less widespread than some of us had expected. If so, then we do need to be very wary indeed about second – and third – waves of transmission. However, antibodies are only one component of immunity and recent studies from Sweden suggest that the prevalence of cellular immune responses to the virus are about twice the prevalence of antibodies. So, exposure may be somewhat higher than the Spanish study suggests, although likely still insufficient to constitute any significant level of herd immunity.

“Evidence is also emerging that exposure to seasonal coronaviruses (common cold viruses) may confer cross-protective immunity to COVID-19; this might explain why some people experience such mild infections.

“The only way we will know for sure if people are immune is when we see whether people who were infected in the first wave are reinfected if there is a second wave.”

Prof Danny Altmann, British Society for Immunology spokesperson and Professor of Immunology at Imperial College London, said:

“The Spanish study is sobering, confirming a picture from many studies around the world, both regional seroprevalence studies and longitudinal studies in recovered patients. The cumulative pool of antibody-positive people barely rises because as some gain immunity, others have lost antibody, perhaps within weeks. This fits with the view that the nature of naturally-induced immunity to SARS-CoV-2 is a rather short-lived antibody response; the other key part of anti-viral immunity, white blood cells termed ’T lymphocytes’ may have memory that lasts several years, but so far we lack the formal proof that they’re protective. Findings such as this reinforce the idea that faced with a lethal infection that induces rather short-lived immunity, the challenge is to identify the best vaccine strategies able to overcome these problems and stimulate a large, sustained, optimal, immune response in the way the virus failed to do. There are dozens of approaches being tested to achieve this.”

‘Prevalence of SARS-CoV-2 in Spain (ENE-COVID): a nationwide, population-based seroepidemiological study’ by Pollán et al was published in The Lancet.  

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