Covid reinfection is more common in people over 65: study findings

LONDON – Most people who have had Covid-19 are protected from contracting it again for at least six months, but elderly patients are more likely to reinfection, according to a peer-reviewed survey published in The Lancet medical magazine on Wednesday night.

The first large-scale study on coronavirus reinfection rates was conducted in Denmark in 2020, with the results confirming that only a small proportion of people (0.65%) returned a positive CRP test twice. PCR tests are seen as the gold standard and tell you whether you currently have the virus.

However, while the previous infection gave children under 65 about 80% protection against reinfection, for people aged 65 and over it gave only 47% protection, indicating that they are more likely to catch Covid-19 again.

The authors of the study – which was conducted by researchers at the Staten Serum Institut and the University of Copenhagen, Denmark, and the European Center for Disease Prevention and Control in Sweden, and received no funding – found no evidence that protection against reinfection decreased over a six-month follow-up period.

The Lancet noted that the researchers’ findings validate strategies that prioritized the protection of the elderly during the pandemic, such as greater social distance and prioritization of vaccines, even for those who recovered from Covid-19.

“The analysis also suggests that people with the virus still need to be vaccinated, as natural protection – especially among the elderly – cannot be considered,” The Lancet said in a press 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.

Although there are previous studies that suggested that immunity to Covid-19, after the previous infection, could last at least six months, this latest survey gives a better indication of the level of protection and how it differs between age groups.

Commenting on the study, Dr. Steen Ethelberg, from the Statens Serum Institut in Denmark, said the research corroborates previous findings about reinfection rates.

“Our study confirms what several others seem to suggest: reinfection with Covid-19 is rare in younger, healthier people, but the elderly are at greater risk of contracting it again. Since older people are also more likely to experience severe symptoms of illness and, unfortunately, dying, our findings make it clear how important it is to implement policies 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, through which more than two-thirds of the population (69%, about 4 million people) were tested in 2020.

The free national PCR test – 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 this data, covering the country’s first and second wave of infections last year, to estimate protection against recurrence of infection with the original Covid-19 strain. Rates of positive and negative test results were calculated taking into account differences in age, sex and time since infection, and were used to produce estimates of protection against reinfection, The Lancet noted.

It is important to note that the authors note that the length of their study means that it was not possible to estimate protection against reinfection with new variants of the virus that emerged at the end of last year. The variant discovered in the United Kingdom has become a dominant strain in Europe, for example, because it is more transmissible.

Further studies are needed to assess how protection against repeated infections may vary with different strains of the virus, the medical journal noted.