Parental Attitudes and Beliefs about Vaccines: Unexpected Effects of a Hepatitis B Vaccination Campaign.

Summary We evaluate the impact of a French vaccination campaign against Hepatitis B (HB) in 1994. Usinga regression discontinuity design, we show that this campaign created an exogenous shock on vaccinationbehavior, increasing the vaccination rate for children aged 11 and above. We also show that this vaccinationscheme led to a decline in the knowledge about HB transmission modes, as well as public confusion aboutthe target population. But our most important result is a drop in measles, mumps, and rubella (MMR)vaccination rate and an increase in the belief that measles is a benign disease. We interpret these results asa salience effect: the focus on HB vaccination may lead to a decrease in the beliefs that other vaccines are asimportant. We find that the decrease in MMR vaccination is mostly due to high-educated parents who aremore likely to substitute MMR with HB for their children, and could have been influenced by their familydoctor. The effect on MMR vaccination was relatively unexpected and may imply a negative externality.Measles is an extremely contagious disease. If the vaccination rate falls, the disease will spread further,raising the question of the net effect of the HB vaccination campaign on the well-being of the population.Overall, it shows the necessity - but also the difficulty- to evaluate the effects of a public policy as a whole,taking into account all potential side effects but also unexpected adverse effects.