Coronavirus survivors who get vaccinated respond up to seven times better to it than those who haven’t had the virus, a study has found.
Researchers found that antibody levels were three times higher in people who had the virus and then one dose of Pfizer’s jab, compared to someone who had never had the virus but had two doses of the vaccine.
The difference was even bigger compared to people who had never had the virus and were given one dose.
The small study was done on 237 mostly female health workers in Sheffield, Oxford, Liverpool, Newcastle and Birmingham.
It measured antibodies and T-cells, which are substances used by the immune system to destroy the coronavirus. Higher levels generally mean stronger immunity.
Scientists found that, after one dose of the vaccine, people who had been infected with Covid in the past had 6.8 times as many antibodies in their blood as those who had not.
They had 2.9 times as many antibodies after one dose as people who had not been infected but who had been given two jabs, the total vaccine course.
But the experts said second doses are still needed for everyone because the booster is thought to make immunity last for longer.
Covid survivors three times the antibody response after one dose of the Pfizer vaccine as people who have not had the virus before but have had two jabs
The study comes after findings in the last few months showed that antibody responses after one dose are significantly higher in people who have had survived Covid.
This most recent study, named Protective Immunity from T-cells to Covid-19 in Health workers (PITCH), was published online.
In it 113 people who had previously had the virus and 103 who had never been infected were given one dose of Pfizer’s vaccine.
And 21 healthcare workers who had not previously had the virus were given two jabs. No Covid survivors were given both doses.
Workers who received both doses were given them three weeks apart, in line with what was done in clinical studies – but the NHS is using a 12-week gap to stretch supplies across more people.
After one dose coronavirus survivors had 5.9 times the number of T-cells — a type of white blood cell that binds to and kills viruses — as those who have never been infected.
Their T-cell response was as strong after one dose as those who had both jabs but had not had the virus.
Professor Miles Carroll, an author of the study and virologist at the University of Oxford, said it was too early to say Covid survivors do not need a second dose.
He said: ‘What you find is that even if people who have been previously infected and have had one dose, some people might have a really good response and some people might have a mediocre response.
‘So having that second dose, even if you were previously infected, is essential to ensure that you have good, solid immunity.
‘And also — what we don’t know — is that it’s likely that second dose will increase the longevity of response even if you’ve had prior infection.
‘So the advice would be to have that second dose.’
And Professor Susanna Dunachie, the chief investigator for the study at Oxford, added: ‘It’s possible in the future, when we’ve seen everyone at six months, we may be able to address that.
‘But right now the safest course of action is to advise the two doses, particularly with the variants of concern.’
The study found no link between age and the levels of T-cell or antibody response after a dose of the vaccine.
Its findings have not yet been peer-reviewed and the authors say further research is needed to determine the long-term effects of vaccines on immunity.
Experts said the study shows the Pfizer jab is successful at both bringing non-infected people’s immunity up and enhancing the range of immune responses in people who had previously had the virus.
Professor Eleanor Riley, and immunologist at the University of Edinburgh, said: ‘This large, well-controlled study of UK health care workers demonstrates that a single dose of the Pfizer-BioNtech Covid vaccine induces antibody and T-cell responses comparable to those seen after natural infection.’
She said the findings back the JCVI’s decision to recommend a 12-week gap between first and second doses in the UK, which has led to criticism in other countries.
Professor Riley added: ‘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.
‘In so doing, [it] enhances the response to several variants of concern including the so-called Kent, South African and Brazilian variants.
‘These data demonstrate the importance of vaccinating everyone, including people who have already been infected.’
And Professor Daniel Altmann, an immunologist at Imperial College London, said: ‘Findings such as this have inevitably led to debate about whether vaccine supplies could be stretched further by offering only a single dose to those known to have been previously infected.
‘For most of the world, including the UK, there may be sufficient diagnostic uncertainty as to who was definitely infected to make this approach hard to implement efficiently.’
Health Secretary Matt Hancock said: ‘The PITCH study presents further proof that vaccines provide excellent protection against the virus.
‘Thanks to the incredible efforts of our vaccination programme, over half of all adults in the UK have had the jab, and we remain on track to offer all adults a vaccine by the end of July.
‘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 or not and I urge everyone to make sure they attend their second appointment — to keep themselves and those around them safe.’
