While there was a "pronounced" lag in antibody production in cancer patients compared with the rate in non-cancer patients, seroconversion occurred in most cancer patients after the second dose, Dr. Irit Ben-Aharon, with Rambam Health Care Campus in Haifa, and colleagues report in JAMA Oncology.
The researchers determined seroconversion rates after the first and second doses of the Pfizer-BioNTech vaccine in 232 patients with solid tumors receiving active anticancer treatment and 261 healthy, age-matched healthcare workers who served as controls.
After the first dose of vaccine, 29% of cancer patients were seropositive compared with 84% of the controls (P<0.001). But following the second dose of vaccine, the seropositive rate reached 86% in the cancer patients.
Cancer patients undergoing chemotherapy showed reduced immunogenicity (odds ratio, 0.41; 95% confidence interval, 0.17 to 0.98).
No cases of SARS-CoV-2 infection were documented during the study period (January 15 to March 14, 2021). However, two cases in the patient cohort were noted immediately after the first dose.
Reported adverse events were similar to data in former trials comprising mostly healthy individuals.
"Despite evolving evidence on the efficacy and safety of SARS- CoV-2 vaccines, there is a paucity of data on patients with cancer who are receiving active anticancer therapy," the study team writes in their paper.
"Although the immunogenicity pattern was gradual and slower than in the noncancer population, after the second dose most patients were seropositive and no documented cases of COVID-19 infection were determined," they report.
"Our study lends credence to the widely adopted recommendation to prioritize patients with cancer for SARS-CoV-2 vaccination. Nevertheless, our results imply that a potential intention to decline a second vaccine by some jurisdictions owing to a shortage of vaccines warrants reevaluation of unique populations, such as patients with cancer, in view of lagging immunogenicity. Until additional prospective data regarding vaccine efficacy in patients with cancer are established, adherence to risk reduction health care strategies is prudent," they conclude.
The study had no commercial funding and the authors have no relevant disclosures.
SOURCE: https://bit.ly/3hqTIbB JAMA Oncology, online July 8, 2021.
By Reuters Staff
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