Hugo Boserup, 22, is undergoing a PCR test for coronavirus as the global outbreak of coronavirus disease (COVID-19) continues in Malibu, California, on December 2, 2020.
Lucy Nicholson | Reuters
LONDON – Most people who have had Covid-19 are protected from getting it again for at least six months, but elderly patients are more prone to reinfection, according to peer-reviewed research published in The Lancet medical diary wednesday night.
The first large-scale study on coronavirus reinfection rates was conducted in Denmark in 2020, with findings confirming that only a small proportion of people (0.65%) returned a positive PCR test twice. PCR tests are seen as the gold standard and tell you if you currently have the virus.
However, while the previous infection gave those under 65 80% protection against reinfection, for people aged 65 and over it provided only 47% protection, indicating that they were more likely to catch again Covid-19.
The authors of the study – which was conducted by researchers at the Staten Serum Institute and the University of Copenhagen in Denmark and the European Center for Disease Prevention and Control in Sweden and received no funding – found no evidence that protection against reinfection has declined over time. six-month follow-up.
The Lancet noted that the researchers’ findings validate strategies that prioritized the protection of the elderly during the pandemic, such as increased social distancing and vaccine prioritization, even for those who have recovered from Covid-19.
“The analysis also suggests that people who have had the virus should still be vaccinated because natural protection – especially among the elderly – cannot be invoked,” the Lancet said in a news release on Wednesday.
To date, the coronavirus pandemic has caused more than 120 million infections and more than 2.6 million deaths, according to Johns Hopkins University.
While there have been previous studies that have suggested that immunity to Covid-19 after a previous infection may last for at least six months, this latest research provides a better indication of the level of protection and the difference between age groups.
Commenting on the study, Dr. Steen Ethelberg of the Statens Serum Institute in Denmark said the research supported previous findings on reinfection rates.
“Our study confirms what a number of others seem to suggest: Covid-19 reinfection is rare in younger and healthier people, but older people are at higher risk of catching it again. and, unfortunately, they are dying, our findings clearly show how important it is to implement policies to protect the elderly during the pandemic. “
The study was conducted by researchers who analyzed data collected as part of Denmark’s national coronavirus testing strategy, through which more than two-thirds of the population (69%, approximately 4 million people) were tested in 2020.
Free national PCR testing – open to anyone, regardless of symptoms – is one of the central pillars of Denmark’s strategy to control the spread of the virus.
The researchers then used these data, including the first and second wave of infections in the country last year, to estimate protection against repeated infection with the original Covid-19 strain. The reports of positive and negative test results were calculated taking into account age, sex and time differences from infection and were used to produce estimates of protection against reinfection, The Lancet noted.
Further studies are needed
It is important to note that the authors note that the time period of their study meant that it was not possible to estimate protection against reinfection with new variants of the virus that appeared at the end of last year. The variant discovered in Great Britain has since become a dominant strain in Europe, for example, because it is more transmissible.
Further studies are needed to assess how protection against repeated infection could vary depending on different strains of the virus, the medical journal said.