Anecdotal reports of Covid reinfection in the UK are growing, including people who tested positive just weeks apart in December and January, or had the virus three or even four times. Children with reinfections are also being seen. We take a look at the science behind catching Covid multiple times.
What is a reinfection?
Reinfection figures usually refer to the detection of a second or subsequent Covid infection, regardless of the variant involved. The risk of reinfection is likely to depend on a number of factors: For example, the data suggest it is higher in unvaccinated people and potentially in those whose previous infection was milder with a lower immune response.
It also depends on the variant: one expert said the risk of reinfection with Omicron soon after a first Omicron infection would be less than Delta followed by Omicron, and how long ago someone was vaccinated. Experts say the dose someone is exposed to can also matter.
The UK Health Security Agency (UKHSA) uses the definition of a potential reinfection as a case 90 days or more after a previous confirmed Covid infection, in part because it excludes those who simply shed the virus for a longer time after infection.
How many reinfections have there been?
According to the latest figures from England From the UKHSA, from the start of the pandemic to January 9 this year there were 425,890 possible reinfections, with 109,936 found in the week ending January 9, representing almost 11% of all cases that week.
Very few possible reinfections are “confirmed” as that requires genetic sequencing. Also, since few people in the community had access to testing in the first wave, many first infections may have been undercounted.
“With the combination of being two years into the pandemic, a few rounds of antibody decline, two big waves of immune evasion by Delta and then Omicron, there’s pretty rampant reinfection,” said Professor Danny Altmann, professor of immunology. at Imperial College London. .
Is it easier to get reinfected with some variants?
In short, yes. According to scientists at Imperial College London, after accounting for a number of factors, Omicron was associated with a 4.38- to 6.63-fold increased risk of reinfection, compared to Delta.
The team adds that this means that protection against catching Covid, arising from previous infection in the last six months, has fallen from about 85%, before Omicron came along, to between 0% and 27%. . The drop is not surprising given that Omicron has been found to have the ability to bypass the body’s immune responses to a significant degree.
Do Omicron reinfections occur in a shorter space of time?
Potentially yes. UKHSA data shows that for cases with a sample date between November 1 and December 29, 2021, there were 2,855 probable reinfections from 29 to 89 days after a previous infection, although some of these may reflect detection in course of an initial infection.
While the UKHSA notes that it is difficult to directly compare the situation between variants, as there are many important changing factors at play, including general levels of immunity in the population, it is likely that Omicron’s immunity evasion powers play a role in these reinfections.
It is not yet clear how well immune responses to Omicron protect 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 following Delta after you’ve developed antibodies to the Omicron spike protein,” said Paul Hunter, a professor of medicine at the University of East Anglia. .
Why has my son had Covid twice this winter?
That could well be due to different variants: according to data from the Office for National Statistics Released in December, schoolchildren with COVID at the time were much less likely to have Omicron than COVID-positive adults. In other words, an earlier recent infection might as well have been Delta, while the latest one is Omicron.
A UKHSA spokesperson said: “The data shows that those who tested positive for coronavirus between 29 and 89 days from a previous infection represent a small proportion of all reinfections. Many of these shorter-interval reinfections are likely to be school-age children because they had the highest levels of infection in September and October, just before Omicron emerged.”
Are reinfections milder?
That may seem logical given the body’s prior immune response, and Hunter notes that the data suggests that viral load in reinfections is lower than in primary infections, suggesting that the illness may be less severe overall. However, the severity of a reinfection depends on many factors, including the variant involved and a person’s vaccination status.
ONS data suggest that when the Alpha variant became dominant, symptoms were less common for reinfections, but this was reversed when Delta became dominant. When Omicron became dominant, the data suggests that people were just as likely to have Covid symptoms on their second infection as they were on their first infection. “There is no shortage of reinfections, some quite serious, although they do not require hospitalizations,” Altmann said.
How many times can people get Covid?
Among those who have had Covid twice are politicians Kier Starmer and Matt Hancock, while there have also been reports of people being infected with Covid three or even four times, some just weeks apart.
The UKHSA does not break down reinfections by episode, although it has identified some possible third reinfections. What is clear is that the longer Covid is with us, the more reinfections a person can experience.
George is Digismak’s reported cum editor with 13 years of experience in Journalism