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.
