COVID-19 boosters shield cancer patients from severe disease

Getting a COVID-19 booster shot yields significant protection against severe disease in patients with cancer, as shown in a large retrospective study.

Monovalent booster vaccine effectiveness was 29.2 percent (95 percent confidence interval [CI], 19.9–37.3) against COVID-19 hospitalization (the primary outcome), 35.6 percent (95 percent CI, 20–48.3) against COVID-19–related ICU admission, and 8.5 percent (95 percent CI, 3.7–13) against COVID-19 diagnosis. [JAMA Oncol 2025;11:999-1010]

The number needed to vaccinate was 166 to prevent one COVID-19 hospitalization, 423 to prevent one COVID-19–related ICU admission, and 110 to prevent one episode of diagnosed COVID-19.

With the bivalent COVID-19 booster, vaccine effectiveness was 29.9 percent (95 percent CI, 19.4–39.1) against COVID-19 hospitalization, 30.1 percent (95 percent CI, 7.7–47) against COVID-19–related ICU admission. The corresponding number needed to vaccinate to prevent one episode of the respective outcomes was 451 and 1,805.

The bivalent vaccine did not provide a statistically significant level of protection against COVID-19 diagnosis (vaccine effectiveness, 2.9 percent, 95 percent CI, −2.6 to 8.2).

“This is the largest epidemiologic study of COVID-19 booster vaccine effectiveness in patients with cancer, a high-risk population of critical importance and uncertain immunologic function,” the investigators said.

They used data from four healthcare systems in the US and established two cohorts of patients with cancer receiving chemotherapy or immunotherapy: 72,831 adults (24.6 percent female) with 34,006 person-years of follow-up during the monovalent COVID-19 vaccine booster period and 88,417 adults (27.8 percent female) with 81,027 person-years of follow-up during the bivalent COVID-19 vaccine period. 

Of the patients, 69 percent received a monovalent booster dose, and 38 percent received a bivalent booster dose.

Vaccine effectiveness did not significantly differ across the cancer types, although the investigators acknowledged that the precision of study estimates for many cancer subgroups was low despite using data with 115,033 person-years of follow-up.

“However, study findings do suggest substantial benefit for all patients with cancer and thus support increased vaccination in all patients in this high-risk group,” they said.

Uptake challenge

At between 38 percent and 69 percent, COVID-19 booster vaccine uptake among patients with cancer was not as high as it should be, the investigators noted. More needs to be done to increase booster vaccination rates in this high-risk population, given the evidence that the vaccines provide substantial protection against severe COVID-19 with a favourable number needed to vaccinate, they added.

To improve uptake, the investigators suggested implementing structured vaccination protocols in oncology clinics. These protocols could include electronic reminders to identify eligible patients, standing orders, and administration of vaccines by nursing staff during cancer care encounters, they said.

Questions remain

Several unanswered questions need to be addressed to improve vaccine COVID-19 vaccine strategy for cancer patients, according to the investigators.

“First, the study did not evaluate potential waning of protection after 4 to 6 months, which has been found in other studies, and thus additional doses of vaccine after 4 to 6 months as recommended are likely to be beneficial,” they noted. [JAMA Oncol 2023;9:1221-1229; N Engl J Med 2021;385:e84]

Additionally, the vaccine effectiveness reported in this study was “modest,” which underscores the need for new or improved vaccine technology that can elicit a stronger and longer-lasting immune response in cancer patients, the investigators pointed out.

“[Finally], the optimal timing of vaccination associated with cancer treatment has not been established… and the mechanisms of reduced antibody responses in patients with cancer still need to be elucidated,” they said.