Corona infection: More and more are becoming infected for the second time.

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Almost eight percent of infections are among people infected for the second time – and the trend is rising. What does this mean for the individual risk?

As the numbers clearly show, reinfections are on the rise due to Omicron: nearly 97 percent of multiple infections were reported in 2022.

While some have yet to contract Covid-19 even after more than two years of the pandemic, the Omicron surge meant their second or even third Corona illness for others. What people observed anecdotally in themselves or their circle of acquaintances is confirmed by an analysis of the numbers: Of a good four million reported infections to date, 322,607 were second infections, and 7402 were third infections. This means that almost eight percent of all people who have recovered from Corona have already had two conditions, and 0.18 percent have even contracted Covid-19 three times – and the trend is still rising.

According to experts, the fact that more and more people are becoming infected more than once is mainly due to the different variants, which undermine immune protection against infection better than their predecessors. A British survey makes this clear: since the dominance of omicron, the risk of reinfection has been 16 times higher. Simulation researcher Niki Popper also observes a development in this country: “You can clearly see that the numbers of two- and multiple-infections caused by Omicron are increasing.” Before Omicron, multiple infections hardly ever occurred; nearly 97 percent of all reinfections were reported in 2022.

This has to do with so-called cross-immunity, explains virologist Christoph Steininger of Med-Uni Vienna: “The more closely two virus types are related, the more likely we are to be protected. With omicron and delta, the difference is so great that a delta infection does not protect very well against an omicron infection.”

Reinfection with other variants
In the long run, experts agree that everyone is likely to become infected with corona multiple times. The number of reinfections will continue to rise. This phenomenon is known from other infectious diseases, says Steininger: “Think of the common cold. There are more than 100 subtypes of rhinoviruses. Everyone has had a cold at some point, yet we get one now and then.” That doesn’t mean, however, that a Covid 19 infection can be compared to the common cold. He stresses, “Corona is a serious infectious disease. The common cold is also milder because we already have broad immunity here.”

Accordingly, it is unlikely that one will be infected twice with the same virus variant, adds Dorothee von Laer, a virologist at Med-Uni Innsbruck: “The probability of being infected a second time with BA.2 after Omicron BA.2 is less than one percent.”

On the other hand, he said those who were infected with Delta or an earlier variant and are not additionally vaccinated are only about 50 percent protected against reinfection with Omicron. Hybrid immune people – those who have been vaccinated and infected – have the lowest risk of reinfection with Omicron, the virologist explains: “They have so many antibodies that they are also very well protected against BA.1 and BA.2.”

This can be assumed, at least based on antibody data; reinfection data are scarce: “From antibody figures, one must also assume that the Omicron variants BA.1 and BA.2 only protect each other to a limited extent. There is some cross-protection, but the probability of reinfection is relatively high,” says von Laer.

Milder courses in the future
According to von Laer, the courses are milder in reinfections than in initial infections because: The more often one has contact with the virus, the broader the immunity becomes. Nevertheless, people should protect themselves as best they can – primarily through vaccination; Steininger appeals: “An infection still offers the risk of a severe course.” In the future, however, courses of Covid 19 disease will become increasingly mild, he predicts: “Because the population will have more and more basic immunity.”