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12 July 2021

New study describes antibody & T cell immune responses to first dose of Pfizer COVID-19 vaccine in people taking immunosuppressant drugs for psoriasis

Ongoing monitoring is needed to determine how effective the Pfizer COVID-19 vaccine is in people taking immunosuppressants.

Results of a new study from researchers at St John's Institute of Dermatology on the antibody and T cell immune responses to the first dose of Pfizer COVID-19 vaccine in people taking immunosuppressant drugs for psoriasis has just been published in The Lancet Rheumatology. A summary of the study is provided below.

St John's Institute of Dermatology logo (website news)Why was the study done?

COVID-19 vaccines work by training and preparing the body’s natural defences – the immune system – to recognise and fight off the virus. Many of the drugs that we use to treat psoriasis – specifically methotrexate and biologics – are called immunosuppressants because they suppress parts of the immune system that are over-active in psoriasis. We do not know whether these drugs also interfere with the helpful parts of the immune system’s response to COVID-19 vaccines.

What did the researchers do?

The researchers investigated the two types of immune response that the human body uses to defend itself against infections such as the virus that causes COVID-19 – antibodies and T cells – in blood samples. They asked people with psoriasis who were taking immunosuppressants to provide blood samples just before, and then 4 weeks after their first dose of the Pfizer COVID-19 vaccine, and then once more, after their second dose. For comparison, people without psoriasis, not taking any immunosuppressants (‘healthy volunteers’) also provided the same schedule of samples. The study ran from 14th January 2021 to 4th April 2021 and a total of 101 people took part - 84 with psoriasis and 17 healthy volunteers.

What did the study find?

Please note that only information from after the first dose of the Pfizer COVID-19 vaccine is available at this stage. The researchers are currently analysing the results from samples taken after the second dose of the Pfizer vaccine and these will be published as soon as they are available.

The researchers found that the level of antibodies against the virus responsible for COVID-19 were lower in people taking immunosuppressant drugs compared to healthy volunteers, with the lowest rate identified in those taking methotrexate.

The researchers also assessed the ability of the antibodies to neutralise the virus. People taking biologics produced antibodies with similar neutralisation capacity against the virus to healthy volunteers. In contrast, people taking methotrexate produced antibodies with lower neutralisation capacity.

T cell responses following the first dose of vaccine were found in all groups, and there was no difference in the strength of response in people taking methotrexate and biologics compared to healthy volunteers. They also found that even if the antibody response was not strong, T cell responses were still detectable.

What does this mean?

The results suggest that biologics do not prevent the body’s immune response to the first dose of the Pfizer COVID-19 vaccine. Methotrexate appears to weaken the antibody response, but not the T cell response. This study also shows that levels of antibodies alone do not tell us enough about the immune system’s complex response to vaccination. All people receiving immunosuppressant drugs should continue to follow all guidance on self-isolation and social distancing as appropriate in line with government guidance. Immune responses may change over time and are also likely to be influenced by the second dose of the COVID-19 vaccine. The researchers (and others) are checking antibody and T cell status again following the second dose and this information is awaited.

You can read the full paper here.

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