Session Item

To evaluate tolerability and immunogenicity of Moderna COVID vaccine in cancer patients (pts) treated with radiotherapy (RT). 

Pts receiving two doses of Moderna vaccine, 28 days apart, treated with exclusive RT in the past 6 months were included in our analysis. A reference group of healthy volunteers receiving vaccine in the same period was chosen post hoc for comparison of tolerance. All participants were surveyed by phone calls 7 days after each dose for early adverse events (AEs), 12-14 and 28 days after each dose for late AEs. Moreover, we collected immunogenicity data in a subgroup of RT pts in terms of anti- SARS-CoV-2 S1 protein Receptor Binding Domain (RBD)IgG antibodies (EliA SARS-CoV-2-Sp1 IgG test, Thermo Fisher, Uppsala, Sweden) seroconversion rates six months after the second dose.

Between March and June 2021 153 pts treated with RT and 185 healthy volunteers were recruited. RT was ongoing in 41 (27%) pts, completed in the previous 3 months for 43 (28%) pts or previous 6 months for 69 (45%) pts. Fifty-one (33%) RT patients had no AEs after the first dose and 57 (38%) had no AEs after the second dose. 30 (20%) RT pts had no AEs after either the first or the second dose. Grade 1 (G1) AEs occurred in 88 (58%) of 153 pts after the first dose and 63 (41%) of 152 pts after the second dose, and grade 2 (G2) or higher AEs occurred in 14 (9%) and 52 (34%) pts after the first and second dose, respectively. Forthy-six (25%) of 185 controls had no AEs after their first dose and 47 (25%) had no AEs after the second dose. 16 (35%) of 46 patients with no AEs after the first dose had no AEs after the second dose. G1 AEs occurred in 130 (72%) volunteers after the first dose and in 75 (41%) volunteers after the second dose. Four (2%) individuals in the reference cohort had late G3 AEs after the first dose and one (1%) after the second dose. Tolerance of Moderna vaccine was not worse in RT pts than in healthy controls both for early AEs (one-sided p=0·46 after first dose and p=1·00 after second dose for grade 2 AEs; p=0·45 after first dose and p=0·99 after second dose for grade 3 AEs; p=0·73 after second dose for grade 4 toxicity), and late AEs (p=0·82 after first dose and p=0·72 after second dose for grade 2 AEs; p=0·17 after first dose and p=0·82 after second dose for grade 3 AEs). Six months after the second dose, we evaluated in 93 RT patients the anti-S1-RBD IgG levels: 6.5%(n=6) had no response (<=40 BAU WHO/mL), and 25.8%(n=24), 50.5%(n=47), 17.2% (n=16) had a moderate (41-200 BAU WHO/mL), good (201-800 BAU WHO/mL) and strong (201-800 BAU WHO/mL) humoral response, respectively. 

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 pts with cancer who received RT in the past 6 months. We showed high level of antibodies in the 67.7% of the population evaluated for the humoral response.