Previous infection does not protect long-term against coronavirus, particularly new variants, study shows

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Having previously been infected by coronavirus does not offer long-term protection against the virus, particularly with new variants of concern, a study has found.

Government research suggests the immune response following natural infection can vary beween individuals six months after catching Covid-19.

The researchers said their findings, which are yet to be peer-reviewed, reinforce the need for everyone to get vaccinated for maximum protection against the virus, as vaccines generate higher immune response than natural infection.

Study author Dr Christina Dold, from the University of Oxford, said: "Our study is one of the most comprehensive accounts of the immune response following Covid-19 in both symptomatic and asymptomatic individuals.

"We found that individuals showed very different immune responses from each other following Covid-19, with some people from both the symptomatic and asymptomatic groups showing no evidence of immune memory six months after infection or even sooner.

"Our concern is that these people may be at risk of contracting Covid-19 for a second time, especially with new variants circulating.

"This means that it is very important that we all get the Covid vaccine when offered even if you think you may have previously had Covid-19."

The Pitch study, funded by the Department of Health and Social Care (DHSC), involved experts from the University of Oxford as well as Liverpool, Sheffield, Newcastle and Birmingham, with support from the UK Coronavirus Immunology Consortium (UK-CIC).

In what is thought to be one of the most in-depth studies of immune memory to date, the researchers looked at how the immune system responds to Covid-19 in 78 healthcare workers who were either symptomatic or asymptomatic.

An additional eight patients who experienced severe disease were included for comparison.

Blood samples were taken monthly up to six months post-infection to examine different elements of the immune response.

These included looking at antibodies as well as cellular response, involving immune cells known as B cells and T cells.

The team found that individuals who showed little or no evidence of immune memory to Covid-19 at six months post-infection were not able to neutralise the Alpha and Beta variants of coronavirus.

This raises the possibility that prior Covid-19 infection does not provide sufficient protection to prevent reinfection by these variants, the researchers said.

The health minister, Lord Bethell, said: "This powerful study addresses the mysteries of immunity and the lessons are crystal clear.

"You need two jabs to protect yourself and the ones you love.

"I call on anyone invited to get vaccinated to step forward and finish the job so we can all get out of this."