Vaccine-related adverse events following ChAdOx1-nCoV-19 vaccine in actively treated patients with solid malignancy, as compared to age-matched healthy controls.

Abstract

e13517 Background: Data on safety of COVID-19 vaccination in malignancy patients, particularly those receiving cancer treatment, is lacking because they are excluded from vaccine trials. We aimed to evaluate vaccine-related adverse events (VRAEs) in actively treated cancer patients. Methods: This prospective, observational study of VRAEs following ChAdOx1-nCoV-19 vaccine among 399 solid malignancy patients on active cancer treatment was conducted in two Thai academic hospitals. Participants received the first dose between June 18 and July 27, 2021 and the second dose at 8-10 weeks later. Solicited and unsolicited VRAEs were collected using questionnaires. The primary endpoint was incidence of VRAEs among solid cancer patients, as compared to healthy controls. Results: 399 cancer patients received cancer treatments during the first dose of vaccine (43% chemotherapy, 34% targeted therapy, 8% immunotherapy, 4% hormonal therapy and 11% combination regimen) and 359 patients continuing the treatments during the second dose. Mean age of the cancer patients was significantly higher than the healthy volunteers (59 +/- 13 vs 48 +/- 13 years, P < 0.001). In overall population, incidence of VRAEs was significantly lower in cancer patients than in healthy controls (57% vs 80%, P < 0.001 in overall periods, 63% vs 93%, P < 0.001 after first dose; and 51% vs 66%, P 0.01 after second dose). In age-matched comparison including 76 cancer patients and 75 healthy volunteers, the incidence of VRAEs in cancer patients was significantly lower than healthy controls only after the first dose (82% vs 93%, P 0.03) but not after the second dose (64% vs 67%, P 0.77) and overall periods (74% vs 79%, P 0.32). There was no significant difference in severity of VRAEs between two groups following the first and second dose. In all patients of cancer cohort, the most common VRAEs were pain at injection site (first dose 39%, second dose 30%), fatigue (first dose 38%, second dose 27%) and myalgia (first dose 33%, second dose 23%). The most common grade 3 VRAEs was fatigue (1%) after the first dose and tenderness at injection site (2%) after the second dose. Fever was the only VRAEs led to interrupting the cancer treatment in two cases (0.5%). Among the cancer treatment types, patients who received a chemotherapy-containing regimen had a lower risk of VRAEs than those who received a non-chemotherapy regimen (odd ratio (OR) 0.2, P 0.001 after first dose and OR 0.4, P 0.001 after second dose). Conclusions: In age-matched comparison,the overall incidence of VRAEs in actively treated patients with solid malignancy following ChAdOx1-nCoV-19 vaccine was comparable to healthy controls. Most occurred VRAEs are mild severity and rarely interfered the cancer treatment. These findings assure that Covid-19 vaccination is safe in cancer patients undergoing treatment.