Reinfections with the coronavirus SARS-CoV-2very rare before the omicron variant, increase the risk of mortality and hospitalization and the likelihood of other adverse health effects, according to a large US study. This increase, moreover, is cumulative, it rises with the number of successive infections.

The study, the first to describe the risks of covid-19 reinfections, is pending peer review in the journal Nature Portfolio, but its authors, Ziyad Al-Aly, Benjamin Bowe and Yan Xie, are known to have published during the pandemic in the prestigious journal ‘Nature’ and other scientific publications relevant research on the cardiovascular effects of coronavirus, reinfections and persistent covid.

The sample of the study – entitled ‘Outcomes of SARS-CoV-2 Reinfection’ and available in the ‘Research Square’ repository – is very broad. Its authors had access to the databases of Veteran Affairs, the health system for Veterans of the armed forces, the largest in the United States, and for which Bowe and Xie work. They matched the records of 250,000 people with one infection, 39,000 with two or more infections and about 5.4 million without infection as a control group. Most are men with an average age of 60 years.

Individuals who had reinfections had an increased risk of all-cause mortality, with a hazard ratio (HR) of 2.14 (i.e., odds multiplied by 2.14) and a excess burden of all-cause mortality of 23.8 per 1,000 people at 180 days. These individuals also showed a higher risk of hospitalization, with an HR of 2.98: that is, that the probability of hospitalization almost tripled. In addition, reinfected individuals exhibited an increased risk of sequelae in the pulmonary and extrapulmonary systems. Thus, reinfection increased the risk of adverse health outcomes such as cardiovascular disorders, kidney problems, gastrointestinal, and musculoskeletal and neurological disorders. In general, the reinfection negatively affected various extrapulmonary organ systems and the respiratory system. They also found that reinfections also increase the risk of developing diabetes, fatigue and mental health problems. All these results were also seen in vaccinated people.


The study has been the subject of comment by leading experts, such as the well-known American doctor and researcher Eric Topol. In an article on the scientific blog he describes as “worrying & rdquor; this work. He recalls that reinfection “was pretty rare before the omicron wave came, 1% or less during the delta wave. But now reinfections have become much more common”. He adds that the omicron subvariants BA.2, BA.2.12.1, BA.4 and BA.5 “have progressively increased immune escape and there is limited cross-immunity with BA.1, the version of omicron with which approximately the half of Americans were infected by early 2022 & rdquor ;.

David N. Fisman, an infectious disease epidemiologist at the University of Toronto (Canada), noted on his Twitter account that “this is a scary document”. He opined that “it is methodologically well done and suggests a ‘cumulative injury’ of successive SARS-CoV-2 infections & rdquor ;.

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Other experts showed some skepticism. This is the case of Professor of Epidemiology Irene Petersen (University College London), who pointed out that “these findings are too bad to be true. It is likely that they are an artifact because of the place where the tests for the reinfected were carried out (in the hospital instead of the community) & rdquor ;.

In any case, the precautionary principle encourages avoiding SARS-CoV-2 coronavirus reinfections as far as possible, which also do not contribute – as a study in the journal ‘Science’ concluded and Faro de Vigo published last Sunday – a robust immune booster.


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