mRNA boosters protect cancer patients against adverse COVID-19 outcomes

A prospective study from Singapore provides evidence of the clinical effectiveness of mRNA-based vaccines against COVID-19 in individuals with cancer.

“In this nationwide cohort study including 73,608 patients with cancer and 621,475 matched controls, the third and fourth [COVID-19] vaccine doses were associated with incremental protection in both groups,” said the researchers. “[Each booster] was associated with significant clinical protection in patients with cancer, lasting at least 5 months in actively treated patients with cancer and cancer survivors, underscoring the benefit of boosters.”

The study was carried out during the predominance of the Delta (between September 15, 2021 and December 20, 2021) and Omicron variants (between January 20, 2022 and November 11, 2022). A majority of the participants received mRNA-based vaccines (ie, mRNA-1273 and BNT162b2). [JAMA Oncol 2023;9:1221-1229]

Of those with cancer, 23,217 were on active treatment while 50,391 were cancer survivors. Mean age was around 62 years, 37 percent were men, and 82 percent were Chinese.

Compared with the two-dose group, those who had three doses obtained significant protection against COVID-19 hospitalization, with lower incidence rate ratios (IRRs) across both Delta (0.24, 0.23, and 0.14 for the active treatment, cancer survivor, and control groups, respectively) and Omicron waves (0.45, 0.27, and 0.29, respectively).

Three doses also conferred protection against severe disease as opposed to two doses during the Delta (IRRs, 0.14, 0.13, and 0.07 for the active treatment, cancer survivor, and control groups, respectively) and Omicron waves (IRRs, 0.29, 0.19, and 0.21, respectively). “[These] provide evidence that patients receiving a third vaccine dose derive additional protection against severe infection from both Delta and Omicron variants,” said the researchers.

Fourth dose provides additional protection

The IRRs during the Omicron wave were even lower following a fourth vaccine dose, both for COVID-19 hospitalization (0.24, 0.15, and 0.21 for the active treatment, cancer survivor, and control groups, respectively) and severe disease (0.13, 0.10 and 0.10, respectively).

These data highlight the potential of a fourth dose to provide further protection against COVID-19 infection necessitating hospitalization, as well as severe disease, irrespective of cancer and treatment status, the researchers noted.

“In particular, the IRR for severe disease was significantly lower during infection 8–59 days after the fourth dose compared with 8–59 days after the third dose, suggesting that a fourth dose provides additional protection,” they said.

Waning of efficacy

There was no significant waning of vaccine effectiveness against COVID-19 hospitalization and severe disease after three COVID-19 vaccine doses across all study groups.

Similarly, no significant waning of vaccine efficacy was reported 60 days after the fourth dose for all outcomes. Of note, only 0.2 percent of patients who received four vaccine doses had severe disease. According to the researchers, this may limit interpretation of results.

Boosters imperative for optimum protection

“The results … provide evidence of the benefit of early vaccination and administration of booster vaccine doses against COVID-19 in patients with cancer, especially in conferring protective effects of vaccination against adverse COVID-19 outcomes,” said the researchers.

The findings also provide insight into the longevity of vaccine-mediated protection against clinical infection outcomes in both the general population and immunocompromised cancer patients with or without active treatment, they continued.