Covid reinfection is rare – but you are at a higher risk if you are over 65 years old
Hugo Boserup, 22, receives a PCR coronavirus test on December 2, 2020 in Malibu, California as the global coronavirus disease (COVID-19) outbreak persists.
Lucy Nicholson | Reuters
LONDON – Most people who have had Covid-19 are protected from getting it again for at least six months. However, older patients are more prone to re-infection. This is evident from peer-reviewed research published in The Lancet Medical Journal on Wednesday evening.
The first large-scale study on coronavirus reinfection rates was carried out in Denmark in 2020. The results confirmed that only a small proportion of people (0.65%) gave a positive PCR test twice. PCR testing is considered the gold standard and will show if you currently have the virus.
While previous infection gave people under 65 about 80% protection against re-infection, it only gave 47% protection to people 65 and over, indicating that they are more likely to catch Covid-19 again.
The authors of the study, which was carried out by researchers from 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 the protection against reinfection within of the country decreased a six-month follow-up period.
The Lancet found that the researchers’ results confirm strategies that have prioritized protecting the elderly during the pandemic, such as: B. increased social distancing and prioritization of vaccines, 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 in the elderly – cannot be relied upon,” The Lancet said in a press release on Wednesday.
To date, the coronavirus pandemic has caused over 120 million infections and over 2.6 million deaths, according to Johns Hopkins University.
While there have been previous studies suggesting that immunity to Covid-19 could last at least six months after previous infection, this latest research provides a better indication of the level of protection and how it differs between age groups.
Dr. Commenting on the study, Steen Ethelberg of the Statens Serum Institute in Denmark said the research supports previous findings on reinfection rates.
“Our study confirms what a number of others seemed to have suspected: reinfection with Covid-19 is rare in younger, healthy people, but older people are at higher risk of recurrence. As older people are also more likely to have severe symptoms Our results highlight the importance of implementing measures to protect the elderly during the pandemic. “
The study was carried out by researchers who analyzed data collected as part of Denmark’s national coronavirus testing strategy, which tested more than two-thirds of the population (69%, around 4 million people) in 2020.
Free national PCR tests, accessible to everyone regardless of symptoms, are one of the central pillars of the Danish strategy to combat the spread of the virus.
The researchers then used these data on the country’s first and second waves of infections last year to gauge protection against repeated infections with the original strain of Covid-19. The ratios of positive and negative test results were calculated taking into account differences in age, sex, and time since infection, and these were used to make estimates of protection from re-infection, according to The Lancet.
Further studies needed
It is important to highlight that the authors note that the time frame of their study made it impossible to gauge protection against re-infection with new variants of the virus that emerged late last year. The variant discovered in the UK has since grown to become a dominant strain in Europe as it is more transmissible.
More studies are needed to evaluate how protection against repeated infections may vary among different strains of the virus, according to the medical journal.