CANCER patients are strongly protected against Covid if they are given Pfizer vaccine doses three weeks apart, a new study has found.

Researchers compared antibody and T cell responses in 205 people, including 151 with solid tumours including lung, bowel, and breast cancer, and those with blood cancers.

Although cancer patients are known to be at increased risk of complications from Covid, uncertainty about how well vaccines will work in patients with severely weakened immune systems means that some cancer patients are not yet being vaccinated.

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However, the study, led by researchers at King's College London and the Francis Crick Institute, found that 95 per cent of cancer patients given two Pfizer vaccine doses three weeks apart showed a strong immune response.

The response was much weaker after a single dose, however, with just 8% of blood cancer patients testing positive for antibodies five weeks on from a single dose, and 43% of those with solid tumours.

Dr Sheeba Irshad, an oncologist and co-author of the paper, said the findings should prompt a review of the 12-week delay for vaccinations in some priority groups, including cancer patients.

She said: "One size does not fit all. Cancer treatments have profound effects on the immune system and cancer patients' immune mechanisms are inferior.

"We need to be concerned about other vaccines for this population too - they do need a second dose quickly."

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The study has not yet been peer-reviewed and was not randomised, so experts caution that further work is needed.

"Data has also not yet been provided for the outcomes among cancer patients given their second dose at 12 weeks, so it is unclear whether a longer interval between jags results in a stronger or weaker immune response compared to three weeks.

Stephen Evans, a professor of pharmaco-epidemiology at the London School of Hygiene & Tropical Medicine, said: “These data will undoubtedly need to be examined by JCVI [UK's Joing Committee on Vaccination and Immunisation], but the evidence that harm has been caused to patients with cancer by delaying a second dose has not yet been demonstrated conclusively."

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Lawrence Young, professor of molecular oncology at Warwick Medical School, said it was concerning that a first dose appeared to leave cancer patients wholly or partially unprotected from Covid, adding: "The study is well-executed but has relatively few cancer patients, particularly in the blood cancer group.

"We need more information on how cancer patients are responding to different vaccines.

"Nevertheless this study does raise the issue of whether patients with cancer, other diseases or those undergoing therapies that affect the body’s immune response (e.g. transplant recipients, rheumatoid arthritis) should be fast-tracked for their second vaccine dose.”