Natural covid-19 infection provides “strong” protection against reinfection for up to eight months, just as a vaccine protects against infection, the World Health Organization (WHO) said in its latest scientific guidance.
The global public health agency, however, said the emergence of ‘variants of concern’ that can evade immunity poses a challenge.
“Current evidence points to most individuals developing strong protective immune responses, following natural infection with SARS-CoV-2. However, inaccurate immunodiagnostic tests may falsely indicate infected individuals as naïve to the virus (not previously infected) or may falsely label non-infected people as positive for immune markers of recent infection,” the WHO’s scientific brief said.
“Available tests and current knowledge do not tell us about the duration of immunity and protection against reinfection, but recent evidence suggests that natural infection may provide similar protection against symptomatic disease as vaccination, at least for the available follow-up period. The emergence of ‘variants of concern’ poses challenges, and their potential to evade immunity elicited by either natural infection or by vaccination needs to be closely monitored,” the document stated.
The WHO said that within four weeks following infection, 90-99% of individuals develop detectable neutralizing antibodies.
The strength and duration of the immune responses are not completely understood and data suggests that it varies by age and the severity of symptoms.
Available scientific data also suggests that in most people immune responses remain robust and protective against reinfection for at least 6-8 months after infection.
The longest follow-up with strong scientific evidence is currently approximately eight months, the WHO said.
The UN agency has also taken note of reinfection. Though rarely reported to date, reinfection can occur, it affirmed in the scientific document.
It cited four large studies from the UK, US and Denmark as estimating that infection with SARS-CoV-2 provided 80-90% protection from reinfection for up to seven months.
The level of protection against reinfection as assessed by PCR positivity was estimated to be 50% in people aged over 65 years. The more the virus circulates, the more opportunities it has to change through natural evolution, it said.
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