Basic principle of population-based cohort study to evaluate influenza vaccine effectiveness among elderly Japanese

Exploring Influenza Vaccine Uptake and Its Determinants among University Students: A Cross-Sectional Study

While vaccination is the only established option to prevent a susceptible host from influenza, we have yet to clarify the decision-making mechanisms of vaccine uptake among Japanese university and college students. We aimed to explore vaccination coverage and the related demographic, sociocultural, and socioeconomic factors among university students. We performed a cross-sectional survey involving 604 students at Hokkaido University. Participants were asked if they received influenza vaccination in advance of the 2018/19 season, and subsequently, their demographic and sociocultural/socioeconomic characteristics were surveyed. We also explored the mechanisms underlying students’ vaccination decisions. Vaccination coverage was estimated at 27.3% (95% confidence interval: 23.7–30.9). Freshmen (p < 0.0001) were significantly associated with choosing vaccination, and their odds ratio of vaccination was 11.3 (95% confidence interval: 6.2–20.7) times greater than students in other years. Among students other than freshmen, students belonging to medicine- and healthcare-related faculties were vaccinated three times more frequently than other students, and the coverage in students from Hokkaido was twice as large as that for students from other prefectures. Moreover, extracurricular activity was a positive predictor of vaccination. Although the coverage was as small as 27.3% among university students, freshmen in Japan have high vaccination coverage, which we believe is associated with the entrance examination during high influenza activity. In addition to exposing students to proper education regarding their risk self-assessment, consciousness raising via appropriate understanding of influenza and its severity and offering vaccination at university health centers at a reasonable cost may promote vaccine acceptance.

Challenges in estimating influenza vaccine effectiveness

Introduction: Influenza vaccination is regarded as the most effective way to prevent influenza infection. Due to the rapid genetic changes that influenza viruses undergo, seasonal influenza vaccines must be reformulated and re-administered annually necessitating the evaluation of influenza vaccine effectiveness (VE) each year. The estimation of influenza VE presents numerous challenges. Areas Covered: This review aims to identify, discuss, and, where possible, offer suggestions for dealing with the following challenges in estimating influenza VE: different outcomes of interest against which VE is estimated, study designs used to assess VE, sources of bias and confounding, repeat vaccination, waning immunity, population level effects of vaccination, and VE in at-risk populations. Expert Opinion: The estimation of influenza VE has improved with surveillance networks, better understanding of sources of bias and confounding, and the implementation of advanced statistical methods. Future research should focus on better estimates of the indirect effects of vaccination, the biological effects of vaccination, and how vaccines interact with the immune system. Specifically, little is known about how influenza vaccination impacts an individual's infectiousness, how vaccines wane over time, and the impact of repeated vaccination.