We’ve known since early on in the pandemic that COVID reinfections could occur. One of the first reinfections reported was in a 33-year-old man from Hong Kong. His initial infection was diagnosed on March 26 2020, with his second infection, with a genetically distinct virus, being diagnosed 142 days later.

Since then reports of reinfection have become common, especially since the emergence of the omicron variant. Early research from South Africa (still in preprint, so awaiting review by other scientists) suggests that the risk of reinfection increased quickly and substantially after the variant arrived.

So why are reinfections increasing? The simple answer is because our immunity is often no longer sufficient to prevent an infection. This can be due to the appearance of a new viral variant like omicron that, because of mutations to its form, is less recognisable to the immune system, meaning the virus bypasses prior immunity. Or it can be because immunity has waned since we were last infected or vaccinated. We know that this is a particular issue with COVID immunity – hence the need for vaccine boosters.

Plus, as I have discussed previously, the coronavirus almost always enters the human body via the nose and throat. Immunity in the mucosal linings of these areas tends to be relatively short lived compared to systemic immunity throughout the body. This may explain why protection against severe illness, usually rooted in the lungs, lasts longer than protection against infection.

How common are reinfections?

The UK has recently started publishing data on reinfections on its COVID dashboard. It classifies a reinfection as someone receiving a new positive COVID test result more than 90 days after their last infection.

Up to February 6 2022, there had been over 14.5 million primary infections and around 620,000 reinfections in England – so one reinfection for every 24 primary infections. Over 50% of all reinfections have been reported in since December 1 2021, suggesting again that the risk of reinfection has increased substantially with omicron.

Read full story at The Conversation: https://theconversation.com/covid-reinfections-are-they-milder-and-do-they-strengthen-immunity-176592

Image courtesy: https://www.shutterstock.com/image-photo/sick-caucasian-man-wearing-face-mask-1673307709