Previous COVID infection boosts long-term immunity and lowers the risk of hospitalisation and death at the same level as vaccination, new peer-reviewed research shows.
The study, led by the University of Washington and published by The Lancet medical journal, is said to be the “most comprehensive study to date” on the impact of natural immunity for the disease.
“For people who have been infected with COVID-19 at least once before, natural immunity against severe disease (hospitalisation and death) was strong and long-lasting for all variants (88% or greater at 10 months post-infection),” researchers said.
However, catching earlier variants was found to offer reduced immunity protection against re-infection with the more transmissible Omicron, which stands at 36% after 10 months.
The research, partly funded by the Bill & Melinda Gates Foundation, included 65 other studies from 19 countries, looking specifically at those who have not been vaccinated.
It suggests the level and length of protection against reinfection, symptoms and severe illness is at least on a par with that provided by two doses of mRNA vaccines like Pfizer and Moderna.
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Researchers also discovered protection from reinfection from a pre-Omicron strain was around 85% at month one, dropping to 79% at 10 months, after analysis of 21 other studies that looked at timescales.
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They did find overall, based on five studies reporting on severe disease (hospitalisation and death), that overall protection remains high for 10 months – 90% for the original, Alpha and Delta strains, and 88% for Omicron.
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Lead author Dr Stephen Lim stressed that vaccines are still the safest way to protect yourself, as “acquiring natural immunity must be weighed against the risks of severe illness and death associated with the initial infection”.
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.”
