Previous Covid-19 infections may not protect people long-term from Covid-19, particularly against variants of concern, research has found.
The Oxford University pre-print study, which has not yet been peer-reviewed, found immune responses of 78 medical staff varied significantly between individuals six months after contracting coronavirus. Some people showed no immune memory at all.
Ninety-two per cent (11 out of 12) of people with asymptomatic disease did not have a measurable immune response six months after infection, while 26% who had symptomatic disease did not.
Study author Dr Christina Dold said: ‘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 researchers took monthly blood samples from the healthcare workers up to six months after infection to study immune response. They looked at antibodies alongside B cells, which keep the body’s immune memory and manufacture antibodies, and T cells, which attack infected cells.
A new machine learning approach – called SIMON – was used to identify patterns in the data and whether initial disease severity and the early immune response could predict long-term Covid protection.
Using this technology, they found an ‘early immune signature’ detectable one month after infection, which predicted the strength of the immune response measured six months after infection. This is the first time such a signature suggesting long-term Covid protection has been found.
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.’
The study also involved experts from Liverpool, Sheffield, Newcastle and Birmingham, with support from the UK Coronavirus Immunology Consortium.
It comes after research in May found a differing immune response has been found in asymptomatic cases compared to more severe cases of Covid-19.
Earlier this month, the Government announced it will require all care home staff to be fully vaccinated against Covid-19 – and is considering extending the policy to NHS staff.