Coronavirus reinfections within months tend to become routine, scientists say

The future of Covid-19 may be a virus that refuses to disappear, which “gives birth” on the one hand new variants capable of escaping in part from the body's defences, and on the other hand successive waves of reinfections two or even three times in the year. This is the fear of some scientists, who see that reinfections of the same person tend to become routine.

The central problem, according to the New York Times, is that the SARS-CoV-2 coronavirus has now become more capable of re-infecting humans. Already those who were infected by the first Omicron variant (BA.1) report second infections from other subvariants, such as Omicron 2 (BA.2), BA2.12.1, BA.4 or BA.5.

These same people may well be infected for a third or fourth time, even this year, according to scientists. In fact, a proportion of these patients - fortunately not a large number - are expected to have persistent symptoms for months or even years (the so-called “long Covid-19”).

“The virus is still evolving and probably many people will have too many reinfections in their lifetime,” estimated epidemiologist Juliet Pulliam of South Africa's Stellenbosch University.

It is difficult to get a clear picture of how widespread the phenomenon of reinfections is already, because many of them go unnoticed as asymptomatic or are not reported by patients to the health authorities. It is, however, certain that reinfections are more frequent after the prevalence of Omicron than with the previous variants.

This is not something that many scientists expected, as before Omicron there was an expectation in the scientific community that vaccination and natural immunity from previous infection would prevent most reinfections. A hope that has been dashed because of Omicron and its sub-variants that manage to evade immune defences. The consequence is that everyone, vaccinated and unvaccinated, is more or less vulnerable to multiple infections (although vaccination continues to significantly reduce the risk of serious illness, hospitalization and death).

“If we continue like this, then most people will be infected at least twice every year. I would be very surprised if that doesn't happen after all,” said virologist Christian Andersen of the Scripps Research Institute in California.

Booster doses - third or fourth - of vaccines reduce the chance of re-infection, but not much. But they do increase immune protection, compared to two doses, in terms of the risk of severe covid-19.

The original scientific assessment was that, as with influenza, the coronavirus would cause a large seasonal wave every year, probably in the autumn, and therefore the best solution would be to revaccinate just before the onset of this wave. Instead, the coronavirus seems to behave more like its “cousins”, the cold coronaviruses, which circulate and cause infections throughout most of the year.

That's why, according to epidemiologist Jeffrey Shaman of Columbia University in New York, ’if reinfection becomes routine, the coronavirus is not just going to be this once-a-year thing that comes along during the winter. Nor is it going to be just a mild nuisance, in terms of deaths it causes.“.

Re-infections with a previous variant, such as Delta, do occur, but are relatively rare. When reinfection does occur, it is very likely that it is a different Omicron. This is not only because each new sub-variant of Omicron has new “aces up its sleeve”, but also because the initial Omicron infection produces a weaker immune response (than, for example, when one was first infected with Delta), so that one's protection weakens more quickly and one is more vulnerable to reinfection by a newer Omicron. The newer subvariants have close affinities, but also enough differences to make reinfection possible in a few months.

The good news is that most of those who are reinfected will not get seriously ill, especially if they have been vaccinated and even with booster doses. So far at least, the coronavirus has not found a way to completely bypass the immune system's defences.

“The big danger,” according to virologist Alex Segal of the Institute for Health Research in South Africa, ‘may come when a variant that is completely different appears.“.

Beyond that, however, there is always the spectre of the “long Covid-19”. It is still too early for scientists to say how often an Omicron infection (or re-infection) due to Omicron can lead to this macarochronic syndrome of persistent symptoms.

In any case, according to the experts, it seems that every year the Covid-19 vaccines should be renewed more quickly than the flu vaccines, so that they can keep track of the changes in the virus. Even an imperfect “match” of a new vaccine with a new variant of the coronavirus will provide better immunity.