The authors of a new work from the Yale School of Public Health and Temple University in Philadelphia have found out the timing of re-infection with coronaviruses for those who have already been ill.

The authors of the new work studied the levels of antibodies in humans, data on which were contained in PubMed and Google Scholar from the moment the database was created until June 30, 2021. There was information about patients who underwent SARS-CoV-2, SARS-CoV, MERS-CoV, HCoV OC43, HCoV-HKU1, HCoV-NL63 and HCoV-229E, as well as the timing of re-infection.

We found one or more studies for each of these viruses providing information on the drop in IgG antibody titers to S-protein, nucleocapsid protein, or whole virus lysate after infection. <…> We then searched PubMed and Google Scholar using the terms phylogeny, phylogenetics, evolution, and phylogenomics, combined with terms from our previous search for articles that contained phylogenetic related information.

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As a result, the authors obtained several sets of data on how immunity resisted re-infection with six coronaviruses from 128 days to 28 years after the first infection. This made it possible to identify typical profiles of falling antibody titers and the risk of recurrence.

As a result of the work, the scientists determined that under endemic conditions – the constant presence in a certain area of ​​the incidence of people with a particular infection – re-infection with SARS-CoV-2 can occur from three to 63 months after the peak values ​​of antibodies. On average, after 16 months.

It is also noted that this period of time was almost two times shorter than for other human coronaviruses. For example, for SARS-CoV, relapse can occur from four months to six years, and for HCoV-OC43, from 15 months to 10 years. 31 months to 12 years for HCoV-NL63 and 16 months to 12 years for HCoV-229E.

Our assessment strongly opposes claims that herd immunity can defeat the epidemic, or that the long-term risks of morbidity and mortality can be reduced without vaccination. Relying on herd immunity without widespread vaccination threatens millions of lives and entails high rates of reinfection and death. For areas with low vaccination rates, our analysis confirms the need for sustained measures such as social distancing, proper indoor ventilation and wearing masks to avoid re-infection.

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