We need to get used to Covid-19 reinfections

We need to get used to Covid-19 reinfections

Even if you have been unfortunate enough to have already had a close encounter with the Sars-CoV-2 virus, your experience with Covid-19 may not be over. Get ready for round two (and third, and possibly fourth, and so on).

In the early months of the pandemic, reinfections were an exceptional event, to the point of making global headlines. "When the pandemic started, everyone thought that once we caught [Covid-19, ed.], That was the end of the matter," explains Juliet Pulliam, director of the South African DSI-Nrf Center for Modeling and Epidemiological Analysis of University of Stellenbosch.

Two years on, this sense of novelty has largely disappeared. The perfect storm represented by the drop in immunity, the relaxation of restrictions and the spread of an extremely contagious variant has made reinfections a normal thing for many people. But even putting these factors aside, it makes sense that the number of reinfections today is higher than ever. In this phase of the pandemic, it was inevitable that repeated contagion would become more common than in the past, due to the huge number of people who have already contracted Covid-19: you cannot be reinfected if you have not been infected for the first time.

Beyond the basic math, it's not surprising that reinfections occur, explains Aubree Gordon, an infectious disease epidemiologist at the University of Michigan: "The virus has changed a lot," he says. If you have been infected with a past variant, Omicron will be largely unrecognizable to your body's immune defenses and more difficult to prevent.

But if reinfections are now an integral part of the future of the pandemic, how frequent are they? Determining the exact number is difficult, due to the decline in testing and reporting, which has made monitoring all types of Sars-CoV-2 infections much more complicated. Also, not everyone defines reinfection in the same way; UK health authorities, for example, require at least ninety days to elapse between the first and second contagion for this to be considered a reinfection. Others, such as the European Center for Disease Prevention and Control, use a minimum interval of sixty days between infections.

Pulliam sought to quantify the number of reinfections. Together with his team, he found that about 15 percent of ongoing infections in South Africa last week were actually reinfections. "And this is almost certainly too conservative an estimate - he adds -, because our surveillance is not optimal and probably many of the first infections escaped us". But looking at the big picture, Pulliam defines the prevalence of reinfections as “quite rare”.

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Arrow Pulliam and his team have also studied how much the change in the scenario is attributable to Omicron. Researchers began monitoring reinfections in South Africa towards the end of the Beta wave (which peaked in January 2021), examining more than 100,000 cases of suspected reinfections. They found that the protection afforded by a first contagion against reinfection remained unchanged throughout the Beta and Delta wave, which peaked the following July. But then Omicron arrived. With the new variant, the risk of reinfection has steadily increased, stabilizing at a higher number.

According to Pulliam, South Africa is in a unique position to study the phenomenon, as it can serve as a barometer for the future of reinfection in the rest of the world, as Omicron has already affected the majority of the population. "If what is happening in South Africa is any indication, people are likely to be reinfected over the years," says Pulliam, who believes reinfection from Covid-19 is set to become a normal part of our lives in the future. >
Other studies have shown how Omicron has changed the picture of reinfections. According to data from the UK, the risk of being infected a second time by Covid-19 has increased about eight times since Omicron became the most prevalent variant in the country. Another paper from Imperial College London, published in December 2021, found that Omicron was five times more likely to reinfect people than when Delta was the dominant variant.

Laith J Abu-Raddad, an infectious disease epidemiologist at Weill Cornell Medical College in Qatar, studied how much a previous infection protects against future reinfection and how much the situation has changed due to Omicron. In a study published in March, Abu-Raddad argues that prior to Omicron, the protection offered by a past infection against reinfection was around 90 percent, both among vaccinated and unvaccinated. After Omicron, the value has dropped to around 50 percent. Reinfections, he says, "are becoming an accepted reality."

It is the large difference between Omicron and previous variants that explains why the risk of reinfection is increased. The virus, however, continues to change, so even if you have been affected by Omicron it is not certain that you will not be able to contract Covid-19 again; not to mention that it is also possible to be reinfected by the various sub-variants of Omicron. In February, in a preliminary and as yet unpublished version of a study, a group of Danish researchers suggested that Omicron's Ba.2 sub-variant could also reinfect people who have recently contracted the original form, Ba.1. However, the study concludes that reinfections of this type are rare. Some of the study participants were re-infected just 20 days after the initial infection, an aspect that, the authors write, casts doubt on using a minimum interval of sixty days to classify a case as reinfection.

Similarly, Alex Sigal, a virologist at the Africa Health Research Institute in South Africa, found a similar pattern in his research, again in a preliminary version. He and his team found that an infection caused by the original version Ba.1 of Omicron offered poor immune protection against the newer versions of the variant, Ba.4 and Ba.5.

New normal WiredLeaks, how to send us an anonymous report This could indicate that the virus is starting to mimic the natural rhythms of other coronaviruses, which infect us many times over the course of our lives. We all get a coronavirus infection about every three years; sometimes even several times in the same year. The Sars-CoV-2 virus may be no different.However, we still don't know if the repeated infections are due to the fact that the initial infection gives us immunity that then vanishes, or if the viruses themselves evolve to overcome the defenses. immune systems that we have built for ourselves. Previous studies that have tried to answer this question lean towards the second hypothesis.

Given the new information we have, according to Sigal, a solution to combat reinfection could be to design a better vaccine. Moderna is already publishing data on a broader recall combining equal amounts of spike proteins from the original and Beta variant, which appears to provide more universal protection against the virus.

The good news is that it is unlikely to develop a severe form of Covid-19 at the next encounter with the virus: Another study by Abu-Raddad found that a reinfection carries a 90 percent less chance of ending up in hospital or dying than the first infection. In any case, it is still good to try not to repeat the experience. While the risk of serious illness or death appears to be much lower when reinfected, that doesn't mean there aren't people dying on the second infection. "It is not a gamble that we should run", warns Pulliam.

Furthermore, Sigal emphasizes, "we do not know what the effects of these repeated cycles of infection will be": the more people harbor the virus, the more it is a dangerous variant is likely to emerge. And on an individual level, it's possible that reinfection could cause long-term damage, such as long Covid. Whether reinfection actually causes long Covid is the most important question, says Pulliam, according to which this aspect will determine whether "in the future we will consider this virus as a simple cold virus - he says - or if we will consider it as something really. serious ".

This article originally appeared on sportsgaming.win UK.

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