Having Omicron doesn’t protect people against reinfection, a new study from Imperial College has found – which explains why cases are still so high.
Earlier in the pandemic, scientists published heartening research that found that people infected with Covid-19 were protected from getting the virus again for at least six months. But Omicron raised questions about Covid reinfection – such as whether you can be infected with a new form of the virus if you’ve already recovered, or how long your increased immunity might last.
The UK Health Security Agency (UKHSA) defines reinfection as a case that’s 90 days or more after a previous confirmed Covid infection.
The Imperial research found there is no immunity boost from catching Omicron, which leaves people at risk of being reinfected sooner and more often – though not with more severe symptoms.
What did the study find?
“The message is a little bleak, ” said Professor Danny Altmann, from Imperial’s department of immunology and inflammation. “Omicron and its variants are great at breakthrough, but bad at inducing immunity, thus we get reinfections ad nauseam, and a badly depleted workforce,”
The researchers looked at blood samples from UK healthcare workers who received three doses of an mRNA vaccine (eg. Pfizer or Moderna) and who had different infection histories to investigate antibody, T and B cell immunity.
The team found that in those who were vaccinated three times and had no previous infection, an Omicron infection did provide an immunity boost against previous variants such as Alpha, Beta, Gamma, Delta and the original ancestral strain of Covid, but not against Omicron, now the dominant strain.
People who caught Covid during the first wave of the pandemic and then again with Omicron also lacked any possible immune boosting, a situation researchers called “hybrid immune damping”.
How and why does Omicron differ from previous strains?
Anthony Fauci, director of the US National Institute of Allergy and Infectious Diseases and chief medical advisor to the US president has stressed that Omicron is “very different” from previous strains.
According to Imperial College scientists, it has a much higher risk of reinfection compared to Delta, but triggers less severe symptoms. This is because Omicron is going through more mutations than Delta and is more transmissible.
Professor Paul Hunter, an expert in infectious diseases at the University of East Anglia, previously told HuffPost UK: “Neither vaccination nor a prior infection provides permanent immunity to subsequent infections. Reinfections are going to become the norm fairly soon if they haven’t already.”
“Other coronaviruses cause repeat infections every three to six years on average, though evidence suggests that reinfection period is much shorter than this,” he added.
Aubree Gordon, an epidemiologist at the University of Michigan, recently told The Atlantic that she estimated each person would catch Covid again around every three years.
She said: “Barring some intervention that really changes the landscape, we will all get SARS-CoV-2 multiple times in our life.”