Retrospective single system analysis of side effects experienced with mRNA (Pfizer-BioNTech and Moderna) vaccinations in immunocompromised cancer patients compared with CDC VAERS database between December 15th, 2020, through July 31st, 2021

ABSTRACT

Background: Immunotherapy is becoming a common therapy in cancer patients. Cancer patients on systemic therapy are a vulnerable population, making them highly susceptible to illness from any infection. The purpose of this study was to collect and analyze data reported by patients regarding the side effects of COVID-19 vaccines (Pfizer-BioNTech and Moderna) in cancer patients with solid tumors receiving immunotherapy. Due to the lack of studies and inclusion of cancer patients in the clinical trials for the vaccine, it is pivotal to investigate of the effects of the SARS-2-CoV vaccine on patients receiving immunotherapy to begin to bridge the current gap in knowledge. Methods: We performed a twophased retrospective analysis of adult patients (age ≥18 years) who received either Moderna or Pfizer-BioNTech COVID-19 vaccinations and were currently on immunotherapy (December 15th, 2020, through July 31st, 2021). Phase 1 included a tertiary health system (n = 15,910) in Northeast Georgia. Phase 2 involved cross-tabulation with the VAERS CDC database to compare results at a national level (n = 374,667). The primary endpoints were severity of side effects, timing of side effects and the relationship between the vaccines. The method to evaluate outcome was the Pearson-Chi-Squared test. Results: Results showed that patients on immunotherapy were more likely to have at least one side effect in the tertiary health system (OR 6.727 [95% CI, 2.748 -16.465] compared to least two side effects in the national dataset (X2 = 7.032, p < 0.05). This difference was driven by the Moderna vaccine recipients, demonstrating a higher likelihood of experiencing two or more side effects (X2 = 6.159, p < 0.05). Those receiving the Pfizer-BioNTech vaccine did not demonstrate statistically significant side effects. The most common reaction noted was weakness in both datasets, which was more likely to occur after the Moderna vaccine. Gender analysis showed no difference in side effects in those receiving immunotherapy. In terms of timing of side effects, patients on immunotherapy (M = 10.66, SD = 25.1) had a delayed side effect onset of 10 days vs. four days. (M = 4.72, SD = 15.5, p < 0.05). Conclusions: Both local and national datasets demonstrate cancer patients receiving immunotherapy compared to those that were on immunotherapy, were more likely to experience mild vaccine side effects, specifically weakness being the most common. There was no statistically significant increase in more serious adverse reactions. Additionally, side effect onset was delayed in patients on immunotherapy. These findings provide a foundation for understanding mRNA vaccines in patients on immunotherapy, with future research needs involving larger sample sizes.