previous Covid infection boosts long-term immunity by about the same amount as a vaccination, according to a new study.
The peer-reviewed University of Washington meta-study, published in the Lancet medical journal, found that past infection also lowered the risk of hospitalisation and death from Covid by about the same amount.
The meta-analysis looked at 65 studies from 19 countries focussing on those who have not been vaccinated.
Analysis of data from 21 studies which studied immunity from reinfection with a pre-Omicron variant estimated that protection against reinfection was around 79 per cent at 10 months.
Protection from a pre-Omicron variant infection against reinfection from the Omicron BA.1 variant was 36 per cent at around 10 months.
However, analysis of five studies reporting on severe disease – meaning hospitalisation and death from Covid – found that protection remained universally high for 10 months: 90 per cent for original Covid, Alpha, and Delta, and 88 per cent for Omicron BA.1.
Six studies which focussed specifically on protection from Omicron-sub variants suggested significantly reduced protection when the prior infection was a pre-Omicron variant.
But if the past infection was Omicron, protection was maintained at a higher level.
“There’s quite a long sustained protection against severe disease and death, almost 90 per cent at 10 months. It is much better than I had expected, and that’s a good thing for the world, right? Given that most of the world has had Omicron,” Dr Chris Murray, director of the Institute for Health Metrics and Evaluation at the University of Washington told CNN.
“It means there’s an awful lot of immunity out there.”
It suggests that protection against reinfection, symptoms and severe illness is at least on a par with that provided by two doses of mRNA vaccines such as Pfizer.
However, researchers stressed that jabs remain the safest way to protect against a Covid infection.
“Vaccination is the safest way to acquire immunity, whereas acquiring natural immunity must be weighed against the risks of severe illness and death associated with the initial infection,” said lead author Dr Stephen Lim.
Co-author Dr Caroline Stein added: “Vaccines continue to be important for everyone in order to protect high-risk populations such as those who are over 60 years of age and those with comorbidities.
“This also includes populations that have not previously been infected and unvaccinated groups, as well as those who were infected or received their last vaccine dose more than six months ago.
“Decision makers should take both natural immunity and vaccination status into consideration to obtain a full picture of an individual’s immunity profile.”
