Researchers at the Universities of Sheffield and Oxford found that even a single dose of Pfizer vaccine generates a robust immune response in 99 per cent of people.

For the study, the researchers analysed 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.

The findings of the study suggested that one dose of the vaccine protects against severe disease. It also supported 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 demonstrated that after two doses levels of protection were even stronger.

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Between 9 December 2020 and 9 February 2021, researchers from the Universities of Sheffield, Oxford, Liverpool, Newcastle, and Birmingham examined blood samples from 237 healthcare workers. This was done to understand their T cell and antibody responses following vaccination from the Pfizer vaccine.

The study also sheds light on the impact of the previous infection from Covid-19 on people's immune response to vaccination.

The findings indicated that Covid-19 survivors showed higher T cell and antibody responses after one dose of the Pfizer vaccine compared to those who had never had Covid-19 before and had one dose of the vaccine.

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The researchers discovered that among people who had had Covid-19 in the past, the T cell response expanded after vaccination to recognize more regions of the Covid-19 spike protein.

However, the researchers are yet to figure out how long T cell and antibody response lasts following infection.

Key findings

The study stated that 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. Antibody responses were 6.8 times higher and T cell responses 5.9 times higher, it added.

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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.

The study also noted that there was no link between age and levels of T cell/antibody response.

The findings of the study were published in the journal The Lancet Infectious Diseases.

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