SG data: Booster mRNA vax shots shield cancer-affected individuals from COVID-19

Administration of booster doses of mRNA-based vaccines provide protection against COVID-19 and its adverse outcomes in patients with cancer who are actively receiving treatment as well as in cancer survivors, as shown in a study from Singapore.

Receiving a third or fourth vaccine dose lowered the risks of COVID-19 hospitalization and severe disease during both the delta and omicron waves, according to the investigators.

Regression analyses showed that compared with being fully vaccinated (two doses), getting boosted (three doses) was associated with lower incidences of COVID-19 hospitalization and severe disease among patients who were receiving treatment for cancer (active treatment group; incidence rate ratios [IRRs], 0.23 and 0.14, respectively), among cancer survivors (survivor group; IRRs, 0.23 and 0.13, respectively), and among individuals without cancer (control group; IRRs, 0.14 and 0.07, respectively) during the delta wave. [JAMA Oncol  2023;doi:10.1001/jamaoncol.2023.2271]

The same was true during the omicron wave, with the corresponding IRRs for COVID-19 hospitalization and severe disease being 0.43 and 0.27 in the active treatment group, 0.26 and 0.18 in the survivor group, and 0.28 and 0.18 in the control group. 

Notably, the incidence of both outcomes during the omicron wave was even lower among participants who received their second booster dose (four doses). This was consistent across the active treatment (IRRs for COVID-19 hospitalization and severe disease, 0.23 and 0.12, respectively), survivor (IRRs, 0.15 and 0.10, respectively), and control (IRRs, 0.19 and 0.11, respectively) groups.

“No waning of vaccine effectiveness against hospitalization and severe disease was seen beyond 5 months after a third dose, nor up to 5 months (the end of this study’s follow-up) after a fourth dose,” the investigators pointed out.

Incremental protection

“The findings of this cohort study provide evidence that patients receiving a third vaccine dose derive additional protection against severe infection from both the delta and omicron variants, consistent with results from previous studies,” according to the investigators. [N Engl J Med 2021;385:1393-1400; Nat Med 2022;28:1063-1071; BMJ 2021;375:e068848; N Engl J Med 2022;386:492-494; Nat Med 2022;28:481-485]

They noted that in the study population, those who were infected more than 150 days after their third dose were not at significantly increased risk of hospitalization and severe disease compared with those infected before 60 days, indicating a sustained protective effect.

“Singapore began administering the fourth dose 5 months following the third, being among the first in the world to do so. After a fourth vaccine dose, the risk reduction of hospitalization and severe disease during the omicron wave was even greater. This suggests that an approach of boosting at regular intervals may be an effective measure against successive waves of COVID-19,” the investigators said. [N Engl J Med 2022;386:2436-2438]

The study included 73,608 patients with cancer (23,217 in the active treatment group and 50,391 in the survivor group) and 621,475 controls matched based on age, sex, race and ethnicity, and socioeconomic status. The mean age of the active treatment, survivor, and control groups were 62.7, 62.9, and 61.8 years, respectively. Among patients with cancer, 27,170 (36.9 percent) were men; 60,100 (81.6 percent) were Chinese, 7,432 (10.1 percent) were Malay, 4,597 (6.2 percent) were Indian, and 1,479 (2.0 percent) were of other races and ethnicities.

Between September 2021 and November 2022, 4,756,102 doses of COVID-19 vaccines were administered to the study population. Of these, 4,462,301 (93.8 percent) were monovalent mRNA vaccines, 76,247 (1.6 percent) were bivalent mRNA vaccines, and the remaining 217,554 (4.6 percent) were non-mRNA vaccines.

“To our knowledge, this study is the first to demonstrate clinical vaccine effectiveness of up to four doses of mRNA-based vaccines against COVID-19 in actively treated patients with cancer and cancer survivors, and matched noncancer controls at a population level,” according to the investigators.

“As the world moves toward living with COVID-19, evidence of the booster third and fourth vaccine dose and efficacy in overcoming waning immunity is imperative to guide the optimum protection for our most vulnerable patients,” they said.