Nearly 50% of blood cancer patients are insufficiently protected against Omicron

Nearly 50% of blood cancer patients do not have detectable levels of antibodies capable of neutralizing the Omicron SARS-CoV-2 variant after a third vaccine dose, according to new laboratory data from the Francis Crick Institute and the Royal Marsden NHS Foundation Trust published as a research letter in The Lancet.

This is the first report of functional immunity against Omicron in a cohort of pancancer patients and the results highlight the importance of a 4th “booster” dose for patients with blood cancers to protect them from the increase in Omicron cases.

In the ongoing CAPTURE study, funded by the Royal Marsden Cancer Charity, researchers monitored the immune responses of hundreds of patients with different types of cancer, after one, two and three doses of the COVID-19 vaccine. *

Using a very precise test, a virus neutralization test developed at Crick, the team measured levels of antibodies that specifically prevent the Omicron variant from infecting cells. The test assesses whether levels of neutralizing antibodies in the blood are sufficient to block at least 50% of viral infection under laboratory conditions.

The results for patients with solid tumors have been very positive. A third dose of COVID-19 vaccine effectively increased the proportion of patients with antibody levels able to neutralize Omicron (90% compared to only 37% after the second dose).** The researchers suggest that these patients can expect at levels of protection similar to people without cancer.

However, when the research team looked at blood samples from patients with blood cancers, they found that people in this vulnerable group were much less likely to have detectable levels of antibodies against Omicron. Only 19% of patients had detectable levels after two doses, and although a third dose was effective for many, 56% of patients benefited from the booster effect.***

UK guidelines already say that adults and children aged 12 and over who are severely immunocompromised should receive three primary doses of the COVID-19 vaccine, followed by a fourth booster dose.

Dr Samra Turajlic, lead author and Crick and Consultant Medical Oncologist group leader at the Royal Marsden NHS Foundation Trust, said: “The pandemic has been particularly difficult for people with cancer and up-to-date information on levels of immunity are particularly important for this vulnerable group.

“We now know that the immune response to vaccines in patients with solid cancers is robust after 3 doses compared to people without cancer, even against the new Omicron variant. But for people with blood cancers, Omicron poses a higher risk. These patients should remain cautious and present for their 4th booster dose as soon as it is available.

“Protecting this vulnerable group is important, particularly in light of the recent easing of COVID-19 restrictions in the UK, such as the end of mandates requiring people to wear face masks. Public health measures must be inclusive and support everyone, including vulnerable people and their caregivers. »

Reference: Fender A, Shepherd STC, Au L, et al. Omicron neutralizing antibodies after third dose of COVID-19 vaccine in cancer patients. The Lancet. 2022. doi: 10.1016/S0140-6736(22)00147-7

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