Immunization and Moral Hazard: The HPV Vaccine and Uptake of Cancer Screening

Direct and crowding-out effects of a Hepatitis B vaccination campaign

We evaluate the direct and spillover causal effects of a Hepatitis B (HB) vaccination campaign in French schools on the vaccination adherence of the targeted pupils. Using a regression discontinuity design, we show that this campaign created an exogenous shock on vaccination behavior, increasing the HB vaccination rate for children aged 11 and above. At the same time, we show a drop in the measles, mumps, and rubella (MMR) vaccination rate of the targeted pupils and an increase in the parental belief that measles is a benign disease. We interpret these results as a salience effect: the focus on HB vaccination leads to a decrease in the belief that other vaccines are as important. 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.

Vaccination and risky behaviors: evidence from the hepatitis B vaccination campaign in China

Understanding the causal relationship between vaccination and individuals' risky behavioral responses has important policy implications as it affects the ultimate effectiveness of increasing access to vaccination. This paper examines the causal effects of vaccination on risky behaviors by exploring the 1992 hepatitis B vaccination campaign in China. Our empirical strategy exploits variations in age at the campaign as well as the pretreatment infection risks across provinces. Using a large cross-section of individuals born between 1981 and 1994, we find that more exposure to the hepatitis B vaccination leads to lower alcohol use during adulthood, and such impacts are almost entirely driven by men. Individuals from more educated families and people who live in urban areas tend to react more. Improved educational attainment and dissemination of related knowledge are important contributors. Our results uncover an unexpected benefit of promoting access to vaccination.

Supplementary Information

The online version contains supplementary material available at 10.1007/s00148-023-00942-4.

Impact of vaccination on the COVID-19 pandemic in U.S. states

Governments worldwide are implementing mass vaccination programs in an effort to end the novel coronavirus (COVID-19) pandemic. Here, we evaluated the effectiveness of the COVID-19 vaccination program in its early stage and predicted the path to herd immunity in the U.S. By early March 2021, we estimated that vaccination reduced the total number of new cases by 4.4 million (from 33.0 to 28.6 million), prevented approximately 0.12 million hospitalizations (from 0.89 to 0.78 million), and decreased the population infection rate by 1.34 percentage points (from 10.10 to 8.76%). We built a Susceptible-Infected-Recovered (SIR) model with vaccination to predict herd immunity, following the trends from the early-stage vaccination program. Herd immunity could be achieved earlier with a faster vaccination pace, lower vaccine hesitancy, and higher vaccine effectiveness. The Delta variant has substantially postponed the predicted herd immunity date, through a combination of reduced vaccine effectiveness, lowered recovery rate, and increased infection and death rates. These findings improve our understanding of the COVID-19 vaccination and can inform future public health policies.

Human papillomavirus vaccine and risky sexual behavior: Regression discontinuity design evidence from Brazil

This study aims to analyze the hypothesis of moral hazard caused by vaccination against human papillomavirus (HPV), regarding girls' beginning of sex life and, once they have begun their sex life, to understand whether it reduces the probability of girls using a condom in their first sexual intercourse. The data are from the 2015 National Survey of School Health (PeNSE). The model used is the regression discontinuity, with the discontinuity in the age of the girls who were able to participate in the public vaccination campaign. The results of the so-called Fuzzy-RDD show that the campaign was effective in increasing the likelihood of vaccination by 26.7-27.6 percentage points. There is no observable effect on young women initiating their sex lives or refraining from using condoms. The results are tested by several robustness methods. This is the first work to use quasi-experimental models in a developing country with low vaccination coverage in Latin America and show that it is necessary to increase awareness campaigns with parents, so they will know that there is no effect of vaccination on the beginning of sex life and condom use.

HPV vaccine status and sexual behavior among young sexually-active women in the US: evidence from the National Health and Nutrition Examination Survey, 2007-2014

Concern has been expressed that human papillomavirus (HPV) vaccination programs might promote risky sexual behavior through mechanisms such as risk compensation, behavioral disinhibition, or perceived endorsement of sexual activity. This study assesses whether HPV vaccination status is associated with any differences in selected sexual behaviors among young sexually-active women in the US. Our dataset includes young, adult female respondents from questionnaire data collected in the National Center for Health Statistics' National Health and Nutrition Examination Survey from 2007 to 2014. The empirical approach implements a doubly robust estimation procedure, based on inverse probability of treatment weighting. For robustness, we implement several specifications for the propensity model and the outcomes model. We find no consistent association between HPV vaccination and condom usage or frequency of sex. Specifically, we find no evidence that HPV vaccination is associated with condom usage or with whether a person had sex more than 52 or more than 104 times per year. We find inconsistent evidence that HPV vaccination is associated with a person having sex more than 12 times per year. As in previous research, HPV vaccination does not appear to have a substantive effect on sexual behavior among young sexually-active women in the US.