Relationship Between Media Coverage and Measles-Mumps-Rubella (MMR) Vaccination Uptake in Denmark: Retrospective Study

"Understanding the relationship between media coverage and vaccination uptake may underpin the design of public health communication strategies and the development of new surveillance strategies."

Convinced that understanding the influence of media coverage upon vaccination activity is valuable when designing outreach campaigns to increase vaccination uptake, these researchers studied the relationship between media coverage and vaccination activity of the measles-mumps-rubella (MMR) vaccine in Denmark. They used historical data on vaccination and media activity over an 18-year period (January 1 1997 to December 31 2014).

Introduced in Denmark on January 1 1987, the MMR vaccination programme consists of 2 vaccinations: 1 for 15-month-old children (MMR-1), and another for 12-year-old children (MMR-2). (Since April 1 2008, the MMR-2 vaccination schedule has changed to reach 4-year-old children.) According to World Health Organization (WHO) statistics for 2016, only 41/160 (25.6%) countries have a coverage of 95% (necessary for maintaining measles elimination) for MMR-2. Several factors influence the success of an immunisation programme. For instance, the safety of the MMR vaccine became a much-discussed topic after 1998 when Wakefield falsely claimed a link between the MMR vaccine and autism. This reduced the public confidence in the vaccine and resulted in a drop in vaccination uptake from above 90% to 79% in England. The uptake of the MMR vaccine has also in Denmark been vulnerable to negative media attention. In 1993, the safety of the vaccine was questioned in a nationwide TV programme, resulting in record low vaccination coverage. Recently, the fear of adverse reactions to the human papillomavirus (HPV) vaccine caused a significant decline in vaccination uptake in Denmark.

The researchers retrieved data on media coverage (1,622 articles), vaccination activity (2 million individual registrations), and incidence of measles for the period 1997-2014. All 1,622 news media articles were annotated as being provaccination, antivaccination, or neutral. Seasonal and serial dependencies were removed from the data, after which cross-correlations were analysed to determine the relationship between the different signals.

Most (65%) of the anti-vaccination media coverage was observed in the period 1997-2004, immediately before and following the 1998 publication of the falsely claimed link between autism and the MMR vaccine. There was a statistically significant positive correlation between the first MMR vaccine and provaccination media coverage (r=.49, P=.004) in the period 1998-2004. In this period, the first MMR vaccine and neutral media coverage also correlated (r=.45, P=.003). However, looking at the whole period, 1997-2014, there were no significant correlations between vaccination activity and media coverage.

The researchers observe that, following the falsely claimed link between autism and the MMR vaccine, provaccination and neutral media coverage correlated with vaccination activity. This correlation was only observed during a period of controversy, which indicates that the population is more susceptible to media influence when presented with diverging opinions. In addition, the findings suggest that the influence of media is stronger on parents when they are deciding on the first vaccine of their children, than on the subsequent vaccine, because correlations were only found for the first MMR vaccine.

In their analysis of the media coverage, the researchers saw that measles outbreaks are one of the strong drivers of provaccination and neutral media content, while antivaccination content is driven by fears of adverse reactions. There is a significant correlation between media coverage and vaccination activity in the period with the most focus on adverse reactions. The researchers hypothesise that because the fear of adverse reactions is hard to relate to everyday life, people are more affected by the media when the discourse is dominated by safety concerns, as in the period 1998-2004. Another explanation for only observing a relationship in the period with a focus on safety may be because it was a period where opposing views on vaccinations were expressed in the media.

Could changes in media coverage have been an early indicator of the reduced public trust in the MMR vaccine? And would this signal be strong enough to launch a proactive information campaign, potentially reducing vaccination distrust and the associated costs? The researchers suggest that, with disinformation being used as a part of cyberwarfare, as well as the easy spreading of fake news, surveillance of traditional media and social media is an essential task for public health authorities. The question is whether new research within natural language processing, information retrieval, and machine learning could be used to automate this process and make it accessible at a low cost.