Moderna Vaccine Appears to be Safe for Those Undergoing Radiotherapy

Patients with cancer who have underwent radiotherapy within 6 months did not experience any notable safety concerns after receiving the Moderna mRNA-1273 vaccine.

The Moderna mRNA-1273 COVID-19 vaccine appears to be well tolerated in patients with cancer who have received radiotherapy within 6 months of vaccination, according to a study published in The Lancet Oncology.

Among patients (n = 153) in the radiotherapy cohort who experienced early adverse effects AEs after receiving the first dose, 5% of patients had grade 2 AEs compared with 4% in the reference cohort. After the second dose, 26% in the radiotherapy group (n = 152) experienced a grade 2 AE compared with 42% of patients in the reference cohort (n = 182).

The most common disease types were breast (49%) and prostate (27%) of patients. A total of 62% of patients had undergone postoperative radiotherapy, 22% had definitive radiotherapy, 9% had stereotactic radiotherapy, and 6% had palliative radiotherapy. Additionally, 27% of patients were receiving ongoing radiotherapy, 28% completed radiotherapy within the last 3 months, and 45% had completed treatment in the last 6 months.

Of the 33 of patients receiving radiotherapy and no AEs were reported after the first dose and 38% had no AEs after the second dose. Investigators also reported that 20% of patients undergoing radiotherapy had no AEs after either the first or second dose.

A total of 58% of patients had grade 1 AEs following the first dose, as well as 41% following the second dose. Additionally, 9% of patients had a grade 2 or higher AE after the first dose and 34% after the second dose. In regard to late AEs after the first dose, 4% of patients had grade 3 injection site reactions. After the second dose, 1 patient had a grade 2 generalized allergic dermatitis in the trunk and legs. An increase in antipyretic pain medication was noted from the first dose (5%) to the second dose (21%) after the second dose (P <.0001.

Twenty-five percent of patients in the control group that had no AEs after their first dose, and 25% had no AEs after the second dose. Additionally, 35% of patients in this group who had no AEs after the first dose also had no AEs after the second dose.

Following the first dose in the control group, 1 patient reportedly had grade 3 injection site pain and 5% had grade 4 fever after the second dose. Two percent of patients had late grade 3 AEs after the first dose, as well as 1 patient after the second dose. Between doses, investigators noted a significant increase in pain medication from 3% after the first dose to 35% after the second dose.

Investigators found among patients who had undergone or are undergoing radiotherapy compared with the healthy controls, the tolerance to the Moderna vaccine was not worse with regard to grade 2 AEs (First dose: one sided P = .46 ; second dose: P = 1.00), grade 3 AEs (First dose: P = .45; Second dose: P = .99), and grade 4 AEs (Second dose: P = .73 a), as well as for the patients who had late grade 2 (First dose: P =.82; second dose: P =.72) and grade 3 AEs (First dose: P =.17; second dose: P =.82 AEs).

“In summary, our data, although based on a small number of patients and limited by the observational nature of the study, showed that the safety profile of the Moderna mRNA-1273 vaccine does not raise any specific concerns in patients with cancer who received radiotherapy in the past 6 months,” the investigators concluded.


Scoccianti S, Delli Paoli C, Grilli Leonulli B, et al. Acute tolerance of Moderna mRNA-1273 vaccine against COVID-19 in patients with cancer treated with radiotherapy. Lancet Oncol. 2021;22(9):1212-1214. doi:10.1016/S1470-2045(21)00427-7