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A persons arm being injected with COVID-19 vaccine

A new study carried out in collaboration with the University of Birmingham with support from the UK Coronavirus Immunology Consortium has found that 99% of people generate a robust immune response against COVID-19 after just one dose of the Pfizer vaccine.

The 'Protective Immunity from T cells to COVID-19 in Health workers' study (PITCH) examined how the immune system responds to COVID-19 after one dose of the Pfizer vaccine among people who have been infected by COVID-19 before and those who have not.

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.

Between December 2020 and February 2021, researchers from the Universities of Sheffield, Oxford, Birmingham, Liverpool, and Newcastle, 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 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.

Professor Paul Moss, UK Coronavirus Immunology Consortium lead from University of Birmingham, said: “Vaccines are a crucial part of our roadmap out of this pandemic. To maximise their impact, it’s critical that we understand the underlying biology of how they induce immunity in different groups of people. 

“When working in a pandemic, time is of the essence. This collaborative approach to science, working with multiple partners at scale, is allowing us to drive forward our knowledge at an unprecedented rate.

“The UK Coronavirus Immunology Consortium, working with PITCH, is a great example of how this team science approach can answer these key questions and help us hasten effective pandemic control.”

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

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.”

Key findings from the PITCH study:

  • Among individuals who had not had COVID-19 in the past and had received two doses of the Pfizer vaccine, T cell response was as strong as people who had had previous COVID-19 infection and one vaccine dose;
  • After one dose of the Pfizer vaccine, individuals who had previous COVID-19 infection showed higher antibody and T cell responses compared with people who had not been infected before. Antibody responses were 6.8 times higher and T cell responses 5.9 times higher;
  • Among individuals who had not had COVID-19 in the past and had received one dose of the Pfizer vaccine, antibody and T cell responses were at a similar or higher level compared to those who had previously been infected but not been vaccinated;
  • There was no link between age and levels of T cell/antibody response.
  • An effective vaccine is one that that saves lives and reduces hospitalisations. Both the Pfizer and Oxford-AstraZeneca vaccines have been shown to be highly effective in reducing COVID-19 infections among older people aged 70 years, according to previously published research carried out by Public Health England. In the over 80s, data suggest that a single dose of either vaccine is more than 80% effective at preventing hospitalisation, around 3 to 4 weeks after the jab.

Further research will continue to deepen our understanding of the immune responses over the longer term and what it means for protection against COVID-19 in the real world.