PITCH study finds strong immune response following first dose of COVID-19 vaccination.

The latest publication to come out of the PITCH study has found that 99 per cent of people generate a robust immune response against Covid-19 after just one dose of the Pfizer vaccine. It suggests one dose of the vaccine protects against severe disease, supporting the decision to delay the second dose and provide protection to as many higher-risk groups as possible by providing more first doses. The study showed after two doses levels of protection were even stronger, underlining the importance of people coming forward for their second dose.

Key Findings

Between 9 December 2020 and 9 February 2021, researchers from the Universities of Sheffield, Oxford, Liverpool, Newcastle and Birmingham analysed blood samples from 237 healthcare workers to understand their T cell and antibody responses following vaccination from the Pfizer vaccine. The study also sheds light on the impact of previous infection from Covid-19 on people’s immune response to vaccination. It found that people who had previously been infected with Covid-19 showed higher T cell and antibody responses after one dose of the Pfizer vaccine compared with people who had never had Covid-19 before and had one dose of the vaccine.

The researchers discovered that among people who had had Covid-19 in the past, the T cell response expanded after vaccination to recognise more regions of the Covid-19 spike protein – which attacks the immune system and causes severe disease. This means, even in those already infected, vaccination from the Pfizer jab provides better protection and an enhanced immune response to Covid-19 than the immune response from natural infection, further supporting the need for a vaccination programme.

It is not yet known how long T cell and antibody response lasts following infection. The first dose of both the Pfizer and AstraZeneca vaccine offer good levels of protection, but to get maximum protection it is vital everyone gets a second dose when invited as two doses of the vaccine will provide longer-lasting protection from the virus.

Key Findings

PITCH lead, Professor Susanna Dunachie, NIHR Global Research Professor at the Nuffield Department of Medicine, University of Oxford, said: “Our study highlights the importance of studying both aspects of immune protection when trying to understand the underlying mechanisms of the immune response to Covid-19 vaccination. Interestingly, we also found that vaccination improves the breadth of T cell responses generated in previously infected individuals. In immunology, this is a good thing as it means that you are more likely to maintain protection against new mutations of the virus, and further work will assess how long these vaccine responses last. It’s still important that everyone follows NHS guidelines to get two doses of the vaccine, even if you think you may have previously had Covid-19.”

“The PITCH Study has been a great opportunity to work collaboratively across five university hospitals and with Public Health England to look at T cell responses to SARS-CoV-2 at greater scale and depth than a single research centre can. By building on the national SIREN Study and putting our heads together, we are contributing towards illuminating the role of T cells in protection against Covid-19 from vaccines and previous infection.”

Professor Paul Klenerman, PITCH study lead from the University of Oxford, said: “T cells are an important component of immunity to viruses – but typically much harder to measure than antibodies. To set this up at scale across the UK in the midst of a pandemic was a big challenge but the very clear data found by PITCH show just how informative this approach can be.”

“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-19 or not, and I urge everyone to make sure they attend their second appointment – to keep themselves and those around them safe.”
Matt Hancock
Health and Social Care Secretary.

Health Minister Lord Bethell, said: “These findings from the PITCH study are crucial to increasing our understanding of the immune response to Covid-19 and how the Pfizer vaccine is working to protect people across the UK already. I urge everyone to come forward to be vaccinated when invited and to take up both doses of the vaccine as both are vital to ensuring long term protection from Covid-19.”

The full publication can be viewed here: https://papers.ssrn.com/sol3/papers.cfm?abstract_id=3812375

Additional information This study formed part of the PITCH Study (Protective Immunity from T-cells in Healthcare workers), which was funded by the United Kingdom’s Department of Health and Social Care. A contribution was also made from the UK Coronavirus Immunology Consortium (funded by UK Research and Innovation and the National Institute for Health Research).
Of the 237 healthcare workers, 113 had previously been infected with Covid-19 compared to 124 healthcare workers who had not. For those who had not previously had Covid-19, 103 were given one dose of the vaccine and 21 were given two doses, with a gap of 23 days between doses. The researchers took blood samples from participants prior to and 28 days after vaccination to measure various aspects of the immune response, including antibodies and T cells. A range of analyses were used to examine aspects of the T cell response including the magnitude of response and the response to different proteins from SARS-CoV-2. Carrying out these T cell analyses is much more complex than antibody studies and difficult to undertake at scale – but this study is the largest and most in depth in the world to date in this field.

1. Polack et al. Safety and efficacy of the BNT162b2 mRNA Covid-19 Vaccine. New England Journal of Medicine 2020; 383(27): 2603-15.
2. Hall et al. Do antibody positive healthcare workers have lower SARS-CoV-2 infection rates than antibody negative healthcare workers? Large multi-centre prospective cohort study (the SIREN study), England: June to November 2020. medRxiv 2021: 2021.01.13.21249642.