COVID immunity is seven times higher if you’ve had the bug and a single dose of Pfizer’s jab, the largest real world study has found.
Experts also discovered just one shot produces a “robust” immune response against the disease in 99 per cent of people.
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It backs up the UK’s approach of spacing out the doses by 12 weeks – leaving Brits very well protected while they await their second shot, and jabbing as many as possible.
They revealed those who already had the virus and were given one shot also have a higher protection against variants.
The study found: “Boosting pre-existing antibody responses with current vaccines could provide protection against viral variants.”
But in contract, the experts noted a single jab in someone who hadn’t been infected before did “neutralise” the South African mutation.
Regardless of age, anyone who had the bug before having a single vaccine had an antibody response 6.8 times higher.
Other key findings included people with no prior infection with two Pfizer doses seeing an immune response as strong as those who had Covid before and had one jab.
From December to February scientists from the Universities of Sheffield, Oxford, Liverpool, Newcastle and Birmingham analysed blood samples from 237 healthcare workers.
They looked into the T cell response in people who have had the bug before, and then had a vaccine.
‘EXCELLENT PROTECTION’
Researchers found the cells – a key part of the immune system that hone in on specific foreign particles – developed a bigger recognition of more parts of the virus’ spike protein, which launches the attack on the body.
This means protection against severe disease is even greater.
But it isn’t clear how long T cell and antibody responses last after infection, so it is still vital to get both vaccine doses to ensure the best protection.
Prof Eleanor Riley, Professor of Immunology and Infectious Disease, University of Edinburgh, said: “This large, well-controlled study of UK health care workers demonstrates that a single dose of the Pfizer/BioNtech Covid-19 vaccine induces antibody and T cell responses comparable to those seen after natural infection.
“As natural infection has been shown to confer greater than 80 per cent protection against reinfection, these data offer considerable reassurance that JCVI’s somewhat controversial decision to recommend a 12 week interval between Covid-19 vaccine doses is a safe, effective and pragmatic approach to maximising public health given current constraints.
“Importantly, this study shows that vaccination of previously infected individuals not only boosts their immune responses but also broadens the repertoire of immune responses to SARS-CoV-2 and, in so doing, enhances the response to several variants of concern including the so-called Kent, South African and Brazilian variants.”
Commenting on the study, Health and Social Care Secretary Matt Hancock said: “The vaccine has already saved thousands of lives in the UK.
“A second vaccine jab is crucial for longer-term protection, regardless of whether you have previously had Covid-19 or not, and I urge everyone to make sure they attend their second appointment – to keep themselves and those around them safe.”
Dr Thushan de Silva, study author from the University of Sheffield, said: “Our study is one of the largest and most comprehensive accounts of the immune response to one dose of Pfizer/BioNTech vaccine comparing previously infected and infection-naive individuals.
“Our results demonstrate that T cell and antibody responses induced by natural infection are boosted significantly by a single dose of vaccine.
“While the response to a single dose was lower in infection-naïve individuals, it was still equivalent or better than the immunity in previously infected individuals before it is boosted by vaccination.”
It comes as England’s top doctor urged over-50s to book their jab before many centres are set to close for weeks.
Professor Stephen Powis’ plea comes as Britain’s looming vaccine supply issues threaten to hamper the country’s jab blitz.
He called on over-50s or any vulnerable adults to book a jab before the NHS stops taking appointments on Monday.
Over-50s can book their vaccine on the NHS website, where they can choose from more than 1,600 jabbing sites across the country.
And Brits aged 18 and over who are clinically vulnerable can also book now.
