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NEW DELHI : Individuals with cancer have an appropriate, protective immune response to Covishield, Moderna and Pfizer covid-19 vaccines without experiencing any more side-effects than the general population, scientists have said. The scientists who presented new research at annual congress of the European Society for Medical Oncology (ESMO Congress 2021), a professional society for medical oncology on Tuesday also said that indirect evidence suggests that a third “booster" shot could further increase the level of protection among this patient population.

The researchers presented several studies published in various peer reviewed journals concluding the effectiveness of covid-19 vaccines among cancer patients. As patients with cancer were excluded from the clinical trials conducted to develop the vaccines and support their authorization for use, the questions of whether the vaccines are safe in this vulnerable population and whether they provide adequate protection against severe forms of covid-19 to individuals whose immune system may be weakened by various anticancer medicines had until now been left open.

To explore the potential impact of chemotherapy and immunotherapy on the protection afforded by vaccination against covid-19, one enrolled 791 patients from multiple hospitals in the Netherlands in four distinct study groups comprising individuals without cancer, patients with cancer treated with immunotherapy, patients treated with chemotherapy and finally patients treated with a chemo-immunotherapy combination, to measure their responses to Moderna’s two-dose mRNA-1273 vaccine.

At 28 days after administration of the second dose, adequate levels of antibodies to the virus in blood were found in 84% of patients with cancer receiving chemotherapy, 89% of patients receiving chemo-immunotherapy in combination and 93% of patients on immunotherapy alone.

According to ESMO press officer Dr Antonio Passaro, lung cancer expert at the European Institute of Oncology in Milan, Italy, not involved in the study, these results compare favourably with the antibody responses seen in almost all (99.6%) of the group of individuals without cancer: “The high rates of efficacy of the vaccine observed across the trial population, regardless of the type of anticancer treatment, constitute a strong and reassuring message for patients and their doctors," he said.

Passaro further highlighted the importance of ensuring complete, two-dose vaccination for patients with cancer to develop enough protective antibodies against the virus, as the trial data also showed that only about one in three of those receiving chemotherapy on its own or in combination with immunotherapy had achieved a sufficient response after their first shot—half as many as in the group of individuals without cancer.

This observation was replicated in another study on the effects of tozinameran (Pfizer–BioNTech) among 232 patients with cancer and 261 control subjects in Israel: while less than a third of individuals with cancer (29%) developed antibodies after receiving the first dose, compared to 84% in the control group, this proportion increased to 86% following administration of the second dose. Further demonstrating the efficacy of the vaccine, only two cases of covid-19 were reported during the study period, both of which occurred in patients who had not yet received their second shot.

Data from one more study presented during the congress additionally showed that out of 585 patients with cancer having received two doses of either tozinameran or AstraZeneca’s covid-19 Vaccine in the UK, those who had previously contracted covid-19 (31%) had higher levels of virus-neutralizing antibodies, including against variants such as Delta, for which vaccination loses some of its effectiveness. This is separately corroborated by another research showing that the antibody response to vaccination was significantly enhanced even after the first dose among patients with cancer who had recovered from covid-19.

Dr Luis Castelo-Branco, medical oncologist, ESMO Scientific and Medical Division, an expert with no ties to the studies, commented: “These findings lend additional support to the principle of offering the complete cycle, possibly including a third booster dose, to patients with cancer to improve their protection, because it suggests their immune system will respond to the extra stimulation."

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