Estimated likelihood of re-infection with coronavirus: “Omicron” plays a big role

by time news

Reports of COVID reinfection in the UK are on the rise, including people who have tested positive just a few weeks apart in December and January, or have had the virus three or even four times. Children are also experiencing re-infection with the coronavirus.

Re-infection figures generally refer to the detection of a second or subsequent COVID infection, regardless of the coronavirus variant involved. The risk of re-infection likely depends on a number of factors: for example, evidence suggests it is higher in unvaccinated people and possibly in those whose previous infection was milder and with a lower immune response.

The likelihood of re-infection with the coronavirus also depends on its variant: according to one expert, the risk of re-infection with Omicron shortly after the first infection with Omicron will be lower than after Delta followed by Omicron. In addition, the circumstance of how long ago a person was vaccinated also plays a role.

The UK Health Safety Agency (UKHSA) uses the definition of possible re-infection as being 90 days or more after a previous confirmed COVID infection, in part because it excludes those who simply shed the virus longer after infection.

According to the latest UKHSA data for England, there were 425,890 possible reinfections between the start of the pandemic and 9 January this year, 109,936 of them in the week of 2 to 9 January, representing almost 11% of all cases in that week.

Very few possible reinfections are “confirmed” as this requires genetic sequencing. What’s more, because few people in the community had access to tests during the first wave of the coronavirus, many early infections may have been overlooked.

“Combined with two years of a pandemic, several rounds of weakening antibodies, two major waves of immunity evasion by Delta, and then Omicron, there is a fairly rampant re-infection,” says Danny Altmann, professor of immunology at Imperial College London.

Is it easier to get re-infected with some variants of the coronavirus? In short, yes. After controlling for multiple factors, Omicron was associated with a higher risk of reinfection compared to Delta, up to 6.63 times, according to scientists at Imperial College London.

The team of researchers adds that this means that protection against COVID infection caused by a previous infection within the last six months has dropped from about 85% before the advent of Omicron to between 0% and 27%. This drop is not surprising given that Omicron has the ability to largely evade the body’s immune responses.

Does re-infection with Omicron occur after a shorter period of time? Potentially, yes., writes The Guardian. Data from the UK Health Safety Agency show that for cases with a sampling date between 1 November and 29 December 2021, there were 2855 likely reinfections between 29 and 89 days after the previous infection, although some of these may reflect ongoing detection initial infection.

Although the UKHSA notes that it is difficult to directly compare the situation between variants – since there are many important changing factors, including the overall level of immunity in a population – Omicron’s ability to evade immunity likely plays a role in these reinfections.

It is not yet clear how well the immune response to Omicron protects against a second Omicron infection or infections with new variants. “I would expect the risk of a second Omicron infection to be much lower than the risk of Omicron infection after Delta, after you develop antibodies to the real Omicron spike protein,” says Paul Hunter, professor of medicine at the University of East England. .

Why did some children have COVID twice this winter? Answering this question, The Guardian writes that this may well be due to different options: according to the Office for National Statistics, released in December, school-age children with COVID at that time are much less likely to receive Omicron than covid- positive adults. In other words, the previous recent infection could very well have been caused by the Delta variant, and their latest by the Omicron.

Are repeated infections easier? This may seem logical given the body’s pre-existing immune response, and Professor Paul Hunter points out that evidence suggests that viral load is lower in reinfections than in primary infections, suggesting that the disease may be less severe overall. However, the severity of re-infection depends on many factors, including the variant involved and the individual’s vaccination status.

Data from the Office for National Statistics suggest that when the alpha variant of the coronavirus became dominant in Britain, symptoms were less common on reinfection, but that changed when it became dominant. “Delta”. And when Omicron became dominant, the evidence suggests that people were just as likely to have COVID symptoms on their second exposure as they were on their first exposure. “There is no shortage of re-infections, some quite severe, though not requiring hospitalization,” says Professor Danny Altmann.

How many times can people get COVID? There have been reports of people contracting COVID three or even four times, some only a few weeks apart. As The Guardian notes, the UK Health Security Agency does not classify re-infections by episode, although they have identified several possible third re-infections. One thing is clear: the longer COVID is with us, the more potential re-infections a person can experience.

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