The Effect of Sex on the Incidence, Latency, Duration and Perceived Burden of Adverse Events Following Seasonal Influenza Vaccination in the Netherlands.

INTRODUCTION: The annual reformulation of the seasonal influenza vaccine results in fluctuating frequencies and severity of adverse effects following immunization (AEFIs), which stresses the importance of pharmacovigilance. Also, sex-related factors are known to influence the development of AEFIs. This study aims to describe the difference in incidence and course (i.e., time-to-onset, time-to-recovery, and perceived burden) of AEFIs between males and females after seasonal influenza vaccination. METHODS: We assessed data from cohort event monitoring studies, which were performed over nine consecutive years (2013-2021), each covering several months during the seasonal influenza campaign in the Netherlands. Participants reported information about AEFIs over a 30-day period in three questionnaires. The effect of sex, age, body mass index, study year, and comorbidities on the incidence of any AEFI, local reactions, fever and the five most reported AEFIs was analyzed using logistic regression. The difference in time-to-onset, time-to-recovery, and perceived burden between males and females was analyzed by the Kruskal-Wallis test. RESULTS: The cohort included 7789 participants (53.0% females). Females had around 2.5-fold (p < 0.001) higher odds of developing any AEFI compared with males. Some study years and comorbidities were positively associated with AEFI incidence, whereas age was negatively associated. An AEFI had a significant shorter time-to-onset, a longer time-to-recovery, and a higher perceived burden in females compared to males. CONCLUSION: Overall, the results confirm that females experience AEFIs more often than males. Additionally, this study shows that the course of AEFIs only partially differs between the sexes.

Tolerability of MenACWY-TT vaccination in adolescents in the Netherlands; a cross-sectional study.

BACKGROUND: In 2018, meningococcal ACWY-TT vaccine (MenACWY-TT) was offered to adolescents in the Netherlands within the National Immunization Programme at 14 years of age. A questionnaire study assessed the tolerability of this vaccine. METHODS: Five thousand adolescents were invited to participate and to fill in two questionnaires about systemic events in the week before vaccination and local reactions and systemic events in the week after vaccination. Frequencies of local and systemic adverse events in the week after vaccination were calculated. Association between the occurrence of systemic symptoms in the week before and after the vaccination was tested by using generalized mixed models (GLMM). RESULTS: Of all adolescents, 139 returned one or both questionnaires. Any local reaction within 7 days after vaccination was reported by 55.6% of the adolescents. Pain (50%) and reduced use of the injected arm (21.3%) were most often reported. Any systemic event was reported by 67.6% of the participants, with myalgia as the most often reported event (37.0%). Compared with the week before vaccination, there were no increased odds of experiencing systemic symptoms in the week after vaccination (OR 0.95; 95%CI 0.40-2.27). CONCLUSIONS: After vaccination with MenACWY-TT vaccine, most adolescents reported one or more adverse events, which were mostly mild and transient. Systemic symptoms were not reported more often in the week after compared to the week before vaccination. Unfortunately, due to a low response rate we were not able to detect the absolute elevated risks the sample size calculation was based on. However, despite limited data, our results are in line with results from prelicensure data, and indicate that MenACWY-TT vaccination is well tolerated in adolescents.