Stronger Responders - Uptake and Decline of HPV-Vaccination in Denmark

The purpose of this study was to identify the "stronger responders" behind the fluctuating coverage with the human papillomavirus (HPV) vaccine in Denmark in order to facilitate information campaigns geared to reach specific subgroups. (Editor's note: The responding variable is the change that happens in an experiment because of something the experimenter is changing to test the truth of a hypothesis.) The idea is that, to regain public trust and target vaccination campaigns, it is could be instructive to unveil the dynamics of these variations in vaccination coverage.

Data from the national vaccination register show that after the introduction of the human papillomavirus (HPV) vaccination programme in Denmark, the first dose coverage for girls born in 1997-2000 was constant at around 90%, and full immunisation coverage was around 80%. However, a decline in coverage started in 2013, and full immunisation coverage reached a mere 15% for girls born in 2004. The decline in coverage followed worries in the lay press and on social media about possible side effects of HPV vaccination. (Editor's note: For example, on March 26 2015, TV2 (one of Denmark's national television stations) aired a Danish documentary on HPV vaccines entitled, "The Vaccinated Girls - Sick and Betrayed". It focused on the condition of 3 girls suffering from serious new medical conditions after being vaccinated against HPV with Gardasil. (Above is an image from news coverage of the documentary.) According the World Health Organization (WHO), an increasing volume of studies have since found that these symptoms have no causal relationship to the vaccine.)

For the study, newspaper articles published from 2006 to 2009 with information about coverage with the HPV vaccine in Denmark were identified from the database Infomedia.dk. Vaccination coverage of recent years was retrieved from the publicly accessible statistics from the State's Serum Institute. Data on average disposable income nationally and for each municipality was retrieved from Statistics Denmark.

According to numbers published in newspapers, girls residing in municipalities with a high disposable income were the first ones to secure the HPV vaccine in Denmark. Years later, at the start of the debate about possible side effects of the HPV vaccine, the decline in vaccination coverage was slightly steeper for girls from high-income municipalities than for girls from low-income municipalities.

The researchers suggest that the difference may be due to factors such as the wealthier part of the population having better access to information and be better positioned to interpret information and, therefore, able to react faster when presented with new information, irrespective of the reliability of the source. In Denmark, the media have been responsible for many headlines concerning severe side effects of the vaccine without presenting any clear evidence. The few press releases from the government about the safety of the HPV vaccine have seemingly simultaneously been neglected and outweighed. Previous studies suggest that the media coverage was the reason for a dramatic increase in influenza vaccinations in the United States, while the media portrayal of possible side effects to the pertussis vaccine in 1974 led to a decline in vaccination participation that led to two major epidemics of pertussis in the United Kingdom. The media's unsubstantiated statements on risks are reinforced when they are disseminated on social media.

Considering that girls living in a municipality with a high average disposable income were trendsetters on the HPV vaccine coverage in Denmark, the government could consider tailoring communications around future vaccination campaigns to more directly reach this group of trendsetters with the hope that they would spread evidence-based information about the vaccine. This, however, raises ethical questions on social discrimination, especially when it comes to a national vaccination programme, which is seen as a basic right regardless of socioeconomic class - and, importantly, the risk of developing cervical cancer is highest in Denmark's lowest socioeconomic groups.

This study fosters new inquiries on the mechanism of losing public confidence in a nationwide vaccination programme, and the question remains on how to restore public trust in the vaccine. Several studies of attitudes towards vaccination have indicated that the family doctor plays a key role when parents decided on whether or not to vaccinate their children. Thus, focusing vaccination campaigns more locally to communicate with family doctors to ensure they are prepared to give girls and their parents neutral and evidence-based information - combined with information specifically geared toward girls in municipalities with high average disposable income - may be part of the solution to a vaccination crisis like the one seen with the HPV vaccine in Denmark.