If you’ve had Covid recently, you’re (probably) feeling a little invincible. After all, we know that infection gives you an immunity boost, and if you’ve had the vaccine, it’s even better.
But, unfortunately, it is possible to get Covid more than once. If you’ve recovered only to see those two little stripes on your lateral flow test again, you’re certainly not alone.
Reinfection is possible even if you’re vaccinated or otherwise healthy. There’s also no guarantee that a second infection will be milder than the first.
It’s one reason why so-called ‘Covid parties’ (like chicken pox parties) are not only dangerous but actually quite pointless.
So, how soon can you be reinfected with Covid?
This is difficult to assess due to the way data is collected. The UK Health Security Agency (UKHSA) defines reinfection as a case that’s 90 days or more after a previous confirmed Covid infection.
“This is to exclude infected individuals who continue to shed virus for a longer time after initial infection,” explains Professor Lawrence Young, a virologist and professor of molecular oncology at Warwick University.
However, this presents challenges for those working to understand more about the virus.
As Professor Paul Hunter, an expert in infectious diseases at the University of East Anglia, puts it: “How do you distinguish between a reinfection after, say, a month and someone who is continuing to shed virus but then catches a common cold? There are certainly reinfections occurring within the 90 day limit, but recognising them as reinfections with the current definition is really difficult.”
Nevertheless, Prof. Young says it is theoretically possible to catch Covid twice within a month. “There is some evidence of reinfection 29 days after a previous infection,” he says, “particularly in school-age children who had high levels of infection late last year before Omicron arrived on the scene.”
What might impact your risk of reinfection?
Some people are more prone to reinfection than others and it depends on a number of factors. Prof. Hunter points towards an ONS report, which found that reinfection is more likely among unvaccinated individuals, and is also more likely to occur when vaccine immunity starts to wane.
“People who were unvaccinated were approximately twice as likely to be reinfected than people who had their second vaccine 14 to 89 days ago,” the reports states. “People who had their second vaccine over 90 days ago were also more likely to be reinfected than people who had their second vaccine more recently from 14 to 89 days ago.”
Prof. Young additionally points out that those who’ve had a lower immune response to a previous Covid infection or to vaccination as a consequence of a weakened immune system are also more likely to be at-risk of reinfection.
“It is also dependent on the type of variant,” Prof. Young adds. “It looks like the risk of reinfection with Omicron soon after a first Omicron infection is lower than after a first infection with Delta.
“The overall risk of reinfection with Omicron compared to other variants is higher due to Omicron’s ability to partially evade immune protection induced by previous infection and vaccination. There is also the effect of waning vaccine-induced immunity that results in increased risk of reinfection over time.”
Will a second Covid infection be less severe?
This, of course, depends on the individual. Virologist Jonathan Stoye of the Francis Crick Institute in London notes that the severity of Covid varies enormously from person to person, and might vary from infection to infection in the same person.
Factors such as the initial dose of virus, possible differences between variants of the disease, the amount of viral load, and changes in a person’s overall health could all affect the severity of a reinfection.
In theory, if you’ve been vaccinated and still have some antibodies from previous infection, the reinfection could well be less severe, but it’s not guaranteed, so taking all the necessary precautions is recommended.