Only from 11.2% of the health personnel of the Hospital Clínic de Barcelona has been infected by the coronavirus. This is a much lower percentage than expected, according to a serological study coordinated by ISGlobal, a center promoted by the “la Caixa” Foundation and a Catalan hospital center.
“This is the first study that measures the prevalence of antibodies against SARS-CoV-2 in a representative sample of health personnel in a country with a high burden of the disease,” said Alberto García-Basteiro, researcher at ISGlobal, a doctor in the International Health Service of the Hospital Clínic and one of the coordinators of the SEROCOV-1 study, according to a statement from ISGlobal and the Hospital Clínic. However, the research team admits that this study is not likely to be representative of other hospitals in Spain, since the Clinic implemented a series of preventive measures earlier.
Knowing the prevalence of infection in healthcare personnel is particularly important, since it also allows determining the risk of exposure in this group and taking measures to reduce it ”
The true percentage of people infected with SARS-CoV-2 remains a great unknown in this pandemic, since infection with this virus causes a wide variety of symptoms, from imperceptible to very serious. “Knowing the prevalence of infection in healthcare personnel is particularly important, since it also allows determining the risk of exposure in this group and taking measures to reduce it,” added García-Basteiro, author of the study.
The research team measured antibodies directed against one of the SARS-CoV-2 proteins in blood samples from 578 people who work at Hospital Clínic. To do this, they developed their own immunological assay using a technology called Luminex, which allows quantifying different types of antibodies with high reliability and against multiple antigens at the same time.
“The advantage of this assay is that we can increase the sensitivity of the test by measuring antibodies of various types and against other viral antigens, since the appearance of each type of antibody is different and the response may vary between individuals,” said Gemma Moncunill. , ISGlobal researcher who shares the main authorship of the study.
This is the first study to measure the prevalence of antibodies against SARS-CoV-2 in a representative sample of healthcare personnel in a country with a high burden of disease. ”
The researchers performed a parallel PCR diagnosis on nasopharyngeal samples to detect active infections. The results reveal that, of the 578 people analyzed, 14 had an active infection (positive PCR) at the time of the start of the study, 39 had been diagnosed by PCR before entering the trial and 54 had developed antibodies against the virus (sign of past or recent infection). Of these 54 people, 21 (that is, 39%) had not been diagnosed at the time of infection, and about half of these undiagnosed people had no symptoms of COVID-19. The total of people who showed evidence of infection, either by PCR or by serology, was 65, that is, 11.2%.
Considering that health workers are a high-risk group, seroprevalence in the population is likely to be even below 11% and still far from the required herd immunity threshold, estimated at around 60%. In any case, we still do not know if the presence of antibodies provides protection against possible reinfections, “said Carlota Dobaño, ISGlobal researcher and senior author of the study.
Taking into account data from a Madrid hospital, where almost 12% of healthcare personnel had already tested positive for PCR at the end of March, and a mathematical model that estimated that 15% of the Spanish population was infected, the observed seroprevalence in this study it is less than expected. “The fact that almost 40% of infections in healthcare personnel were undiagnosed underscores the importance of performing PCR tests on all staff, whether or not they have developed symptoms, in order to reduce the risk of virus transmission in the hospital context ”, has insisted Alfredo Mayor, ISGlobal researcher and also senior author of the research.
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