Understanding the shift in COVID-19 vaccine hesitancy and its associated factors for primary and booster doses among university students: A cross-sectional study.

BACKGROUND

Vaccine hesitancy (VH) poses a major challenge to achieving high COVID-19 vaccination rates. Universities, with mandatory primary dose policies but optional boosters, offer a unique setting to study VH dynamics. This study aimed to estimate COVID-19 VH prevalence and identify key factors influencing VH across primary and booster doses among university students.

METHODS

In this cross-sectional study, all actively enrolled students at the University of Waterloo, Ontario, Canada, during Winter 2024 were invited to complete an online survey. Means and standard deviations were calculated for VH scores and proportions were calculated for the binary VH. Differences were compared using paired t-tests and chi-square. Generalized Estimating Equations was applied to model changes in VH scores from primary to boosters and identify key predictors of VH. Interaction terms were tested to evaluate dose-specific effects on VH.

RESULTS

Among 4453 respondents, VH prevalence increased from 17 % for primary doses to 33.4 % for boosters, with higher VH scores for boosters (Mean ± SD: 10.9 ± 8.1) than primary doses (Mean ± SD: 7.3 ± 7.1). Women (aOR = 1.06, 95 % CI 1.01-1.11) and younger students (aOR = 1.62, 95 % CI 1.25-2.10) showed the largest VH increases, especially for boosters. Students with low perceived risk, negative perceptions of boosters' safety and effectiveness, low intention to follow government recommendations, and no prior flu or meningococcal vaccination exhibited the greatest VH increases when shifting from primary to booster doses. Conversely, students with no religious affiliation and those whose decisions were unaffected by mandates showed smaller changes in VH.

CONCLUSION

The rise in VH from primary to booster doses appears driven by demographic, psychological, and behavioral factors. Tailored interventions that promote clear communication, improve access, and strengthen confidence in booster recommendations rather than reliance on mandates are critical for reducing VH and sustaining vaccine uptake in this population.