Covid survivors have three times the antibody response to a single dose of the vaccine, study finds


Coronavirus survivors who are vaccinated respond to it up to seven times better than those who have not had the virus, a study finds.

Researchers found that antibody levels were three times higher in people who had the virus and then shot one dose of Pfizer, compared to someone who had never been infected but received two doses of the same vaccine.

The difference was even greater when they looked at people who had never caught Covid and who only received one dose.

But the experts claimed that the single dose triggered a “robust” immune response in 99 percent of people. They said protection levels are even stronger after the reboot, underscoring the importance of people coming forward for their second shot.

The findings support the UK’s policy of rapid rollout of a single dose of vaccine to provide coverage to millions of Britons in higher risk groups as soon as possible, researchers say.

The survey was conducted among 237 health professionals in Sheffield, Oxford, Liverpool, Newcastle and Birmingham. Most of the volunteers were women.

It measures levels of both antibodies and T cells, substances used by the immune system to destroy the coronavirus. Higher levels generally mean stronger immunity.

Scientists found that people who had been infected with Covid in the past had 6.8 times as many antibodies in their blood after one dose of the vaccine as those who did not.

They had 2.9 times as many antibodies after one dose as people who were not infected but who received two injections, the total vaccination course.

But the experts said everyone still needs a second dose, as the booster is thought to make immunity last 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 shots

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 shots

The study comes after findings in recent months have shown that antibody responses are significantly higher after a single dose in people who have survived Covid.

The new study, called Protective Immunity from T-cells to Covid in Health workers (PITCH), was published online.

In it, 113 people who had previously contracted the coronavirus and 103 who had never been infected, received one dose of Pfizers vaccine.

And 21 health workers who had not previously had the virus received two injections. Neither dose received Covid survivors.

Workers who received both doses received them three weeks apart, consistent with what was done in clinical trials that approved it in December.

But the NHS is using a 12-week period to expand supplies to more people, after UK regulators insisted it was safe to do so.

After one dose, the survivors of the coronavirus had 5.9 times as many T cells – a type of white blood cell that binds to viruses and kills them – than those who have never been infected.

Their T cell response was just as strong after one dose as those who had both injections but had not had the virus.

Professor Miles Carroll, a virologist from the University of Oxford and author of the study, said it was too early to say that Covid survivors do not need a second dose.

He said, ‘What you find out is that even if people who have been infected before and have had one dose, some people can have a really good response and some people a mediocre response.

So having that second dose, even if you were previously infected, is essential to make sure you have good, solid immunity.

Pictured: Rae Mackenzie received his first coronavirus vaccine at Lewis Sports Center in Stornoway, Scotland yesterday

Pictured: Rae Mackenzie received his first coronavirus vaccine at Lewis Sports Center in Stornoway, Scotland yesterday

Pictured: Rae Mackenzie received his first coronavirus vaccine at Lewis Sports Center in Stornoway, Scotland yesterday

And also – what we don’t know – is that it is likely that that second dose will increase the response time, even if you have had a previous infection.

“So the advice would be to take that second dose.”

And Professor Susanna Dunachie, the lead investigator on the Oxford study, added: ‘It’s possible in the future, if we’ve seen everyone after six months, we might be able to do something about that.

“But right now, the safest way is to advise the two doses, especially with regard to the variants in question.”

The study found no association between age and levels of T cell or antibody response after a dose of the vaccine.

The 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 that the Pfizer vaccine is successful in both increasing the immunity of uninfected people 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 professionals shows that a single dose of the Pfizer-BioNtech Covid vaccine induces antibody and T cell responses similar to those which are observed after natural infection. ‘

She said the findings support the JCVI’s decision to recommend a 12-week period between the first and second dose in the UK, which has sparked criticism in other countries.

Professor Riley added: “Importantly, this study shows that vaccination of previously infected individuals not only enhances their immune response, but also broadens the repertoire of immune responses to SARS-CoV-2.

‘By doing this, [it] reinforces the response to several variants of concern, including the so-called Kent, South African and Brazilian variants.

‘These data show how important it is to vaccinate everyone, including people who are already infected.’

And Professor Daniel Altmann, an immunologist at Imperial College London, said, “ Findings such as these have inevitably sparked debate as to whether the vaccine supply could be further expanded by offering just a single dose to those known to have previously are infected.

“For most of the world, including the UK, there may be enough diagnostic uncertainty about who was actually infected to make this approach difficult to implement efficiently.”

Health Minister Matt Hancock said: “The PITCH study provides further evidence that vaccines provide excellent protection against the virus.

“Thanks to the incredible efforts of our vaccination program, more than half of all adults in the UK have had the shot, 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 shot is crucial for longer-term protection whether you’ve had Covid before or not, and I urge everyone to make sure they get to their second appointment – to themselves and those around them to protect.’


A significant amount of research has suggested that people infected with Covid and recovered may only need one injection of the vaccine to be immune to the virus.

However, few peer-reviewed studies on this topic have been published – with vaccines only available since December at the earliest – and most of the data has been released in prepress.

And some studies have suggested that Covid may be more likely to cause worse side effects from the vaccine.

Here’s what studies have said about how Covid survivors respond to different doses of the vaccine:


One dose of coronavirus vaccine can give Covid survivors as many as two doses to people who have never had the infection

Researchers at the University of North Carolina-Chapel Hill compared antibody levels between two groups of patients who received the Pfizer-BioNTech vaccine or the Moderna vaccine.

The study, published on the pre-print server, looked at 193 healthcare personnel who were eligible for the vaccine as of mid-December 2020.

Professor Allison Aiello, an epidemiologist at the UNC Gillings School of Global Public Health said: ‘We found that the antibody response to a single dose of vaccine was almost twice as high in subjects previously infected as in subjects with no signs of previous infection. ‘


Researchers at the Fred Hutchinson Cancer Research Center in Seattle found that a single vaccine injection boosted antibodies and other immune system cells up to 1000-fold in Covid survivors.

For the research, published on pre-print server, the team looked at blood samples from 10 coronavirus survivors who donated plasma.

Blood samples were examined in each of them before and after a single dose of the Pfizer-BioNTech or the Moderna vaccine.

The results showed a significant jump in the levels of two types of white blood cells – B and CD4 + T cell responses, which help mediate immunity.


Researchers at the Icahn School of Medicine at Mount Sinai in New York have pre-printed in February suggests that Covid survivors only need one dose of vaccine.

They found that Covid survivors who received one injection had antibody levels comparable to – and even higher than – those who had never been infected and received two doses.

In addition, virus survivors were more likely to report adverse reactions after being immunized, such as injection site pain, fever, and fatigue.


Figures from the ZOE Covid-19 Symptom Study app show that 33 percent of people already affected by the virus had at least one mild side effect.

In comparison, the rate was only 19 percent among non-Covid patients.

The most common side effect was fatigue, at nine percent. It was followed by headaches (eight percent) and chills (four percent).

Meanwhile, the data also showed that most side effects – known as systemic because the whole body is affected – appeared within 48 hours of vaccination.