The contagious nature of a vaccine scare: How the introduction of HPV vaccination lifted and eroded MMR vaccination in Denmark

Abstract

BackgroundHuman papillomavirus (HPV) vaccine coverage was high in Denmark until it plunged following negative media coverage. We examined whether the decline in HPV vaccination undermined uptake of another adolescent vaccine, measles, mumps and rubella (MMR). MethodsThe Danish national health register provided data on uptake of MMR vaccine dose 2 (at age 13) for children born from 1991 to 2003 (n = 827,716). The primary exposure variable comprised three time periods: before HPV vaccine introduction, during high HPV vaccine coverage, and after the drop in HPV vaccine coverage. To examine the effect of HPV vaccination on MMR2 uptake, we estimated MMR2 uptake by age 13 using logistic regression, controlling for gender, birth month, birth year, and maternal education. FindingsMMR2 vaccination coverage was high for both girls and boys (86% and 85%) in 2009. Following the introduction of HPV vaccine for girls in 2009, MMR2 coverage increased for girls even as it decreased for boys (gender gap 4·6 percentage points, 95% CI 4·3 to 4·8). Coverage with MMR2 for girls continued to be high over the following four years, and almost all girls (91%) who received MMR2 vaccination also received HPV1 vaccination within the same week. When negative media coverage led to a decline in HPV vaccination, MMR2 uptake for girls also declined. By 2015, MMR2 coverage for girls and boys had become similar again (80% and 79%). Families with the highest level of maternal education showed the strongest decline in MMR2 coverage for girls. InterpretationConcomitant vaccine provision can increase overall vaccine uptake. However, reduced demand for one vaccine may reduce concomitant vaccination and undermine resiliency of a country’s vaccination program. FundingDrs. Gørtz and Ejrnæs appreciate generous funding from the Novo Nordisk Foundation (grant no. NNF17OC0026542) and from the Danish National Research Foundation through its grant (DNRF-134) to the Center for Economic Behavior and Inequality (CEBI) at the University of Copenhagen.