Boston—Since the beginning of the COVID-19 pandemic, concerns have been raised about risks for cancer patients. Additional questions were raised with the availability of vaccines and evidence that they were less effective in that cohort.

Now, a new study has sought to determine which cancer patients get meaningful protection from the vaccines and which do not.

"Although patients with cancer have poor COVID-19–related outcomes, the effectiveness of SARS-CoV-2 vaccination in this population is unclear because they were excluded from vaccination trials," according to new research published in JAMA Oncology. "Recent studies suggest that patients with cancer mount less robust antibody responses to vaccination than immunocompetent controls. The objective of this retrospective cohort study in the national Veterans Affairs (VA) health care system was to estimate the SARS-CoV-2 vaccination effectiveness in patients with cancer in a real-world setting during the 140-day period following initial vaccine availability."

For the cohort of VA patients who received systemic therapy for cancer between August 15, 2010, and May 4, 2021, a proxy measure for effectiveness of the vaccine starting 14 days after the second dose was determined to be 58%. In addition, the authors pointed out that the measure of effectiveness beginning 14 days after the second dose was 85% in patients who had not received systemic therapy within the 6 months prior to vaccination and 76% among those who had received hormonal treatment.

"Results suggest that SARS-CoV-2 vaccination associated with lower infection rates in patients with cancer, especially in those not receiving current systemic therapy and those receiving hormonal treatment," the authors write.

Their retrospective, multicenter, nationwide cohort study of SARS-CoV-2 vaccination and infection among Veterans' Health Administration patients was conducted from December 15, 2020, to May 4, 2021. Included were all adults with solid tumors or hematologic cancer who received systemic cancer-directed therapy from August 15, 2010, to May 4, 2021, and were alive and without a documented COVID-19 positive result as of December 15, 2020.

For the study, researchers each day matched newly vaccinated patients 1:1 with unvaccinated or not yet vaccinated controls based on age, race, and ethnicity, VA facility, rurality of home address, cancer type, and treatment type/timing.

Defined as the primary outcome was documented SARS-CoV-2 infection. A proxy for vaccine effectiveness was defined as 1 minus the risk ratio of SARS-CoV-2 infection for vaccinated patients compared with unvaccinated controls.

Of the 184,485 patients who met eligibility criteria, 113,796 were vaccinated. Of these, 29,152 vaccinated patients—median [IQR] age, 74.1 [70.2-79.3] years; 95% were men; 71% were non-Hispanic white individuals matched 1:1 to unvaccinated or not yet vaccinated controls.

Researchers report that, as of a median 47 days of follow-up, 436 SARS-CoV-2 infections were detected in the matched cohort—161 infections in vaccinated patients versus 275 in unvaccinated patients. While 17 COVID-19Ðrelated deaths occurred in the vaccinated group, 27 were documented in the unvaccinated group.

"Overall vaccine effectiveness in the matched cohort was 58% (95% CI, 39% to 72%) starting 14 days after the second dose," the authors advise. "Patients who received chemotherapy within 3 months prior to the first vaccination dose were estimated to have a vaccine effectiveness of 57% (95% CI, –23% to 90%) starting 14 days after the second dose vs. 76% (95% CI, 50% to 91%) for those receiving endocrine therapy and 85% (95% CI, 29% to 100%) for those who had not received systemic therapy for at least 6 months prior."

While, in general, COVID-19 vaccination was associated with lower SARS-CoV-2 infection rates in patients with cancer, researchers caution, "Some immunosuppressed subgroups may remain at early risk for COVID-19 despite vaccination, and consideration should be given to additional risk reduction strategies, such as serologic testing for vaccine response and a third vaccine dose to optimize outcomes."

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