Coronavirus sufferers who have recovered may ‘lose immunity within six months’

Coronavirus patients who have recovered from the disease may lose their immunity to Covid-19 within six months, new research has suggested.

An analysis of patients with four similar viruses found re-infection in occurred frequently and on average a year after the initial contraction.

One patient was struck down with the illness 17 times, the report claimed, which is the equivalent to once every two years.

Corresponding author Dr Lia van der Hoek, of Amsterdam University Medical Centres, said the results need to be taken into account when developing vaccination or natural herd immunity.

Dr Van der Hoek said: "Caution may be needed when relying on policies that require long-term immunity – such as vaccination or natural infection to reach herd immunity.

"Re-infection times varied between six months and almost nine years.

"They were frequently observed at 12 months after the initial infection."

Dr van der Hoek's investigation is the first of its kind and she and colleagues looked at 10 case studies of seasonal coronaviruses monitored over 35 years.

All four strains – known as HCoV-NL63, HCoV-229E, HCoV-OC43 and HCoV-HKU1 – cause respiratory tract infections like Covid-19.

To find out how often seasonal coronavirus infections occur, they examined more than 500 blood samples collected at regular intervals since the 1980s.

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All participants were healthy adult males living in Amsterdam and had levels of antibodies which can destroy the virus peaked swiftly after the onset of symptoms.

Dr Van der Hoek said: "Covid-19 may share the same pattern after the pandemic. Re-infections occur frequently for all four seasonal coronaviruses.

"It suggests it may be a common feature for all human coronaviruses – including Covid-19."

She added: "A key unsolved question in the Covid-19 pandemic is the duration of acquired immunity.

"Insights from infections with the four seasonal human coronaviruses might reveal common characteristics applicable to all human coronaviruses.

"We monitored healthy individuals for more than 35 years and determined that reinfection with the same seasonal coronavirus occurred frequently at 12 months after infection."

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