COVID-19 Vaccine Booster Uptake and Effectiveness Among US Adults With Cancer.

Key Points: Question: How effective were additional doses of COVID-19 vaccines at preventing COVID-19 hospitalizations among persons with cancer from January 2022 to August 2023? FINDINGS: In a retrospective cohort study among persons with cancer in the US, additional monovalent COVID-19 vaccines reduced COVID-19 hospitalizations by 29%, with a number needed to vaccinate of 166 in January to August 2022, and a bivalent COVID-19 vaccine reduced COVID-19 hospitalizations by 30%, with a number needed to vaccinate of 451 in September 2022 to August 2023. Meaning: In both time periods, COVID-19 vaccination was associated with protection from severe COVID-19 among persons with cancer. Importance: Persons with cancer are at increased risk of severe COVID-19 infection, but the additional benefit of COVID-19 boosters is unclear. OBJECTIVE: To assess COVID-19 vaccine effectiveness (VE) and number needed to vaccinate (NNV) among persons with cancer of an additional dose of the monovalent COVID-19 vaccine. Design, Setting, and Participants: Retrospective cohort study conducted in 4 health care systems in the US among persons with cancer receiving chemotherapy or immunotherapy. Statistical analysis was conducted between March 2023 and August 2024. Exposures: Receipt of an additional dose of the monovalent COVID-19 vaccine before January 1, 2022, with follow-up until August 31, 2022, and the bivalent COVID-19 vaccine from September 1, 2022, to August 31, 2023. Main Outcomes and Measures: COVID-19 hospitalization, diagnosed COVID-19, and COVID-19–related intensive care unit (ICU) admission. RESULTS: Among 72 831 persons with cancer (17 922 female individuals [24.6%]), 69% received a monovalent booster by January 1, 2022. During 34 006 person-years of follow-up, the COVID-19 hospitalization rate was 30.5 per 1000 person-years among patients who received a monovalent booster vs 41.9 per 1000 person-years among patients who received the primary series alone, with an adjusted VE of 29.2% (95% CI, 19.9%-37.3%) and NNV to prevent 1 COVID-19 hospitalization of 166 (95% CI, 130-244). There was also significant VE to prevent diagnosed COVID-19 (8.5% [95% CI, 3.7%-13.0%]) and COVID-19–related ICU admission (35.6% [95% CI, 20.0%-48.3%]). Among 88 417 persons with cancer (24 589 female individuals [27.8%]) with 81 027 person-years of follow-up during the bivalent period, patients who received this booster (38%) had a COVID-19 hospitalization rate of 13.4 per 1000 person-years vs 21.7 per 1000 person-years among persons who did not receive a bivalent vaccine, with an adjusted VE of 29.9% (95% CI, 19.4%-39.1%) and NNV to prevent 1 COVID-19 hospitalization of 451 (95% CI, 345-697); the adjusted VE was 30.1% (95% CI, 7.7%-47.0%) to prevent COVID-19–related ICU admission. Conclusions and Relevance: In this retrospective cohort study, COVID-19 booster vaccinations were associated with significant protection against severe COVID-19, with a favorable NNV among persons with cancer. However, uptake of COVID-19 vaccine boosters was low, and interventions are therefore justified to increase COVID-19 uptake in this high-risk population. This retrospective cohort study examines the uptake and effectiveness of COVID-19 booster vaccines in preventing hospitalizations due to severe COVID-19 infection among patients with cancer.