The study entitled, 'The MMR-Autism Controversy: Did Autism Concerns Affect Vaccine Take Up?' will be presented during the 4th Biennial Conference of the American Society of Health Economics in Minnesota on June 10-13.
The researchers discovered that fewer parents decided to vaccinate their children in the US following concerns about an alleged association between the MMR vaccine and autism. The allegation has been widely deemed as false. However, according to Lenisa Chang, assistant professor of economics in UC's Carl H. Lindner College of Business, the MMR-autism controversy that was widely portrayed in the media following a publication in a medical journal in 1998 caused a decline of approximately 2% in MMR vaccinations in 1999 and 2000. The decline continued despite later studies providing substantial evidence against the purported claim.
Chang used data from 1995 to 2006 from the National Immunization Survey to assess the response with regard to the controversy surrounding the allegation of the MMR vaccine being linked to autism.
She discovered after the controversy the likelihood of a child being vaccinated against MMR decreased with higher levels of the mother's education, meaning that in comparison with non-college educated mothers, those who had a college education were less likely to vaccinate their children. The phenomenon may be explained by higher educated mothers having better access or having a better understanding of the medical information portrayed in the media.
However, after the MMR-autism link was refuted in epidemiological studies, the difference in MMR vaccination rates between lower and higher educated mothers continued, becoming even more prominent in 2003, 2004 and 2006. This may be due to the fact that parents felt uncertain in terms of vaccinating their child, given that the earlier negative information may have been perceived as more significant in comparison with the positive information they received later.
Chang furthermore discovered that the source of the controversy was an article in the medical journal The Lancet, which published the research that was later discredited of MMR vaccine being linked to a risk of autism. The articles appeared to raise the question regarding the safety of other vaccines, like those for polio or other vaccines that contained measles.
According to Chang, the decline is a substantial decrease caused by the 'spillover effect' of parental concerns. She says:
"The spillover effect I find on other vaccines such as polio and, to a lesser degree DTP (diphtheria, tetanus and pertussis), could be partially ascribed to general safety concerns toward all vaccines that stemmed from the MMR controversy, but other factors might be at play as well."
Chang is currently studying the impact on immunization rates of state mandates, which orders insurance companies to cover childhood vaccines.
Written By Petra Rattue