Determinants of undervaccination of routine childhood immunization in Argentina: A cross-sectional study.

Routine childhood immunization is one of the most effective methods of preventing infectious diseases in children. In Argentina, there has been a decline in routine immunization coverage since 2015, with very little evidence to date on underlying drivers of this steady decline. We administered an online nationwide behavioral insights survey in Argentina between July 1-25, 2022, targeting parents with at least one child under the age of 12 years. Our survey included 1504 parents, 7% (n = 111) of whom did not or only partially vaccinated their children. We found that, compared to the youngest parents (aged 18-24), older parents were less likely to under-vaccinate their children (e.g., 30-34 year-old parents: adjusted Odds Ratio (aOR): 0.31, 95% Confidence Interval (CI) 0.16-0.57). Parents who undervaccinated their children were more likely to take vaccination advice from parent and wellness social media influencers (parent influencers: aOR 2.51, 95% CI 1.46-4.31), and were less likely to trust the social media accounts of official health organizations (aOR 0.82, 95% CI 0.70-0.96). Furthermore, these parents had heightened concerns about routine immunizations, including the number of vaccines given to children and potential for adverse side effects. When asked whether they knew enough to make a vaccine decision for their children, parents who undervaccinated their children were more likely to report that they did not know enough about vaccines or the vaccination schedule to make a decision. These results offer important insights into parental concerns surrounding routine childhood immunization and suggest potential drivers of - and solutions to - the decline in routine immunization seen in Argentina since 2015.