Invited Commentary: The Use of Population Attributable Fractions in Studies of Vaccine Hesitancy

Vaccine hesitancy-the delay or refusal of vaccines despite their availability-has been linked to lower vaccination rates and outbreaks of vaccine-preventable diseases. Using cross-sectional surveys of 78,725 parents and other family members in the United States, Nguyen et al. (Am J Epidemiol. 2022;191(9):1626-1635) calculated the population attributable fraction (PAF) of vaccine hesitancy on nonreceipt of recommended childhood vaccines, including influenza vaccine. The PAF is readily calculated: p(rr - 1)/rr, where p is the proportion of those hesitant among nonvaccinated individuals, and rr is the risk ratio of nonvaccination between those hesitant over those nonhesitant. By vaccine, the PAF ranged from 6.5% for nonreceipt of the hepatitis B vaccine birth dose to 31.3% for nonreceipt of the diphtheria-tetanus-pertussis vaccine dose 3. For nonreceipt of influenza vaccine, the PAF varied geographically, with relatively high values in some Northeast (e.g., New York at 22.6%) and Northwest (e.g., Oregon at 23.0%) states and lower values in certain Southern (e.g., Louisiana at 7.5%) and Mountain West (e.g., Utah at 8.8%) states. The PAF can elucidate the contribution of vaccine hesitancy on nonvaccination in different circumstances. Future studies can apply this technique in different populations and incorporate different measures of vaccine hesitancy.