15 March 2021

Cancer patients may need their second dose of COVID-19 vaccine in three weeks, not 12 weeks, British researchers reported last week.

A study, still to be peer-reviewed, found that many cancer patients experienced little protection from a single dose of the Pfizer mRNA vaccine. However, for patients with solid tumours, a second dose within three weeks gave significant protection.

Researchers at King’s College London were unable to quantify the benefits of the second dose for patients with blood cancer, but say these patients should also get a rapid second booster.

The team compared immunity outcomes for 151 patients enrolled in a study of cancer patients and the COVID-19 virus. They were able to compare outcomes after UK guidelines on booster doses changed at the end of December, recommending that the second booster shot should be delayed from three weeks to 12 weeks after the first dose.

The researchers found that three weeks after vaccination, just 39% of patients with solid tumours had antibody responses as did only 13% of those with blood cancers. For comparison, antibody responses were found in 97% of a control group of volunteers without cancer.

The researchers then found that among patients with solid tumours who received a second booster dose in the three-week interval, 95% had antibody responses. There wasn’t enough evidence to confirm whether this was also the case for blood cancer patients.

They also found no benefit from delaying the booster jab as antibody levels declined over time – becoming detectable in just 8% of blood cancer patients after five weeks.

Co-senior researcher Dr Sheeba Irshad said: “Based on our findings, we would recommend an urgent review of the vaccine strategy for clinically extremely vulnerable groups. Until then, it is important that cancer patients continue to observe all public health measures in place such as social distancing and shielding when attending hospitals, even after vaccination.”

Co-senior researcher Professor Adrian Hayday said: “The vaccine is very impressive in its impact on healthy individuals and our study shows that it can clearly bring immense benefit to cancer patients too, but in most cases, this is only after boosting.

“Cancer patients should be vaccinated and boosted quickly and their responses, particularly those of blood cancer patients, should be intensively monitored so that those who mix with family, friends and carers can be confident of their environment.”

The Royal College of GPs said it was seeking “urgent” guidance about the findings from the government.

Chair Professor Martin Marshall said: “It’s important to note that these findings apply to patients with cancer and that the evidence for other patients continues to suggest that the first dose of the vaccine provides a good level of protection.”

Source: King’s College London

Link: https://www.kcl.ac.uk/news/delaying-second-vaccine-dose-cancer-patients-vulnerable-virus

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