In a study reported in JAMA Oncology, Wu et al found that vaccination with SARS–CoV-2 messenger RNA vaccines reduced the incidence of COVID-19 infection vs no vaccination in Veterans Affairs (VA) patients with cancer. Vaccine effectiveness varied according to time between last systemic therapy and vaccination.
Study Details
The retrospective study involved data on SARS–CoV-2 vaccination and infection among patients in the VA health-care system from December 15, 2020, to May 4, 2021. All adults with solid tumors or hematologic malignancies who received systemic cancer-directed therapy from August 15, 2010, to May 4, 2021, and had no documented SARS–CoV-2 positive test result as of December 15, 2020, were eligible.
Each day between December 15, 2020, and May 4, 2021, newly vaccinated patients were matched 1:1 with unvaccinated controls based on age, race and ethnicity, VA facility, rurality of home address, cancer type, and treatment type/timing. Vaccine effectiveness was defined as 1 minus the risk ratio of SARS–CoV-2 infection for vaccinated vs unvaccinated patients.
Key Findings
A total of 29,152 patients who received at least one dose and 18,312 who received both doses were matched 1:1 with unvaccinated controls.
In this cohort study, COVID-19 vaccination was associated with lower SARS–CoV-2 infection rates in patients with cancer. Some immunosuppressed subgroups may remain at early risk for COVID-19 [infection] despite vaccination, and consideration should be given to additional risk-reduction strategies….— Wu et al
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At a median of 47 days of follow-up, SARS–CoV-2 infection was detected in 161 vaccinated patients vs 275 controls. COVID-19–related deaths occurred in 17 vs 27 patients.
Overall vaccine effectiveness in preventing infection after the first dose was 42% (95% confidence interval [CI] = 28%–53%). Overall vaccine effectiveness starting 14 days after the second dose was 58% (95% CI = 39%–72%).
Vaccine effectiveness starting 14 days after the second dose was 66% (95% CI = 48%–79%) in patients with solid tumors and 19% (95% CI = −68% to 65%) in those with hematologic malignancies. Effectiveness rates were 85% (95% CI = 29%–100%) among patients who last received systemic therapy more than 6 months before vaccination, 63% (95% CI = 23%–87%) among those treated 3 to 6 months prior to vaccination, and 54% (95% CI = 28%–72%) among those treated within 3 months before vaccination.
Vaccine effectiveness rates among patients receiving treatment within 3 months before vaccination were 57% (95% CI = −23% to 91%) among those receiving chemotherapy-containing therapy, 29% (95% CI = −84% to 75%) among those receiving targeted therapy, and 76% (95% CI = 50%–91%) among those receiving endocrine therapy.
The investigators concluded, “In this cohort study, COVID-19 vaccination was associated with lower SARS–CoV-2 infection rates in patients with cancer. Some immunosuppressed subgroups may remain at early risk for COVID-19 [infection] 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.”
Nathanael R. Fillmore, PhD, of the VA Boston Healthcare System and Dana-Farber Cancer Institute, is the corresponding author for the JAMA Oncology article.
Disclosure: The study was supported by a Stanford Cancer Institute Innovation Award, VA Office of Research and Development, Department of Defense, National Institutes of Health, and others. For full disclosures of the study authors, visit jamanetwork.com.
