Although uncommon, co-infections of COVID-19 occur, especially in people aged 65 and over – underscoring the importance of continued physical distancing and prioritization for vaccines, even in previously infected people, a large observational study yesterday The Lancet suggest.
Researchers at the Statens Serum Institut in Copenhagen, Denmark, have data on 10.6 million SARS-CoV-2 tests from 4 million Danes (69% of the population) from that country’s second COVID-19 surge, of 1 September to 31 December 2020, analyzed. They then compare it to infection rates of residents with positive or negative tests during the first boom, March to May 2020.
Before June 2020, 533,381 residents were tested, of which 2.20% were positive for COVID-19. Of the 525,339 people eligible for follow-up during the second boom, 2.11% were infected during the first boom, and 0.65% tested positive again. In comparison, 3.27% of the 514,271 tested negative during the first boom were infected (adjusted relative risk [aRR], 0.195). The protection against reinfection was 80.5%.
An alternative cohort analysis of COVID-19 infection rates during the year in those with a previous infection versus one three months earlier or more yielded similar estimates (aRR, 0.212), for a 78.8% protection. However, among residents aged 65 and older, the protection against reinfection was only 47.1%.
Older people, the researchers said, may be more likely to re-infect due to the age-related weakening of immunity, disrupting the coordination of coronavirus-specific T cell responses and the scarcity of naive T cells, linked to aging and poor COVID. -19 outcomes.
‘Natural protection cannot be relied upon’
There was no difference in estimated protection against re-infection by sex (78.4% in men versus 79.1% in women) or evidence of fading protection over time (79.3% after 3 to 6 months of follow-up versus 77.7% at 7 months follow-up or more). The study only covered the original coronavirus strain; variants were not evaluated.
In a sensitivity analysis of a sample limited to 15,604 doctors, nurses, social workers and medical assistants, who in 2010 tested a median of ten times, of which 658 (4.2%) tested positive during the first surge. Of the 658, 1.2% were re-infected during the second surge, compared with 6.2% of those who tested negative during the first surge (aRR, 0.189; estimated protection against recurrent infection, 81.1%).
“Because the older age group is more prone to a serious clinical course of disease, this finding highlights the need to introduce protective measures for the older population in the form of effective vaccines and increased physical distance and infection control, even in those who are known. previously infected, ”they wrote.
Study co-author Steen Ethelberg, PhD, said in a Lancet press release that their findings could inform policy on vaccination strategies and the relaxation of public health restrictions. “As older people also experience more severe disease symptoms and sadly die, our findings make clear how important it is to implement policies to protect the elderly during the pandemic,” he said.
The authors stated that a better understanding of the extent and length of protection, as well as the mechanisms of immunity, against recurrent coronavirus infection is critical for formulating optimal intervention strategies. “Our data indicate that vaccination of previously infected individuals should be done because natural protection cannot be relied upon,” they wrote.
The release calls it the first large-scale study of its kind.
Vaccination is a lasting solution ‘
In a commentary in the same journal, Rosemary Boyton, MBBS and Daniel Altmann, PhD, of Imperial College London, said that the quality and durability of the protection produced by natural COVID-19 infection is weaker than the higher concentrations of neutralizing antibodies generated by currently available vaccines – a finding complicated by coronavirus variants capable of eliciting both natural and vaccine-induced immune responses.
“Interestingly, even after single doses, vaccine responses are significantly improved in individuals with a history of SARS-CoV-2,” they said. “All these data are a confirmation, if necessary, that the hope for protective immunity through natural infections for SARS-CoV-2 may not be within our reach, and a global vaccination program with high-efficiency vaccination is the lasting solution. “