Impact of a dTcaP booster vaccine awareness campaign initiated by the French national health insurance for adults aged 25 years in 2021

This study found that the awareness campaign run by the CPAM did not improve the uptake of the dTcaP booster for adults aged 25 years. These findings may be inconsistent with existing literature on the effectiveness of patient reminders for vaccinations [11] and in other areas of prevention. For cancer screening programs, several studies reported increased adherence through the use of email invitations including a meta-analysis study evaluating different strategies to increase the participation of women in breast cancer screening via letter, telephone calls, home visits and informational brochures [13].

Since this study was conducted in 2021, the effects of the COVID-19 pandemic may have limited the uptake of the dTcaP booster vaccine and corresponds with Rachlin et al., that found a 3% decrease for routine practices of other vaccinations in 2021 [14]. In other words, although the COVID-19 pandemic led to the succession of new vaccinations and boosters, the vaccination program to protect against COVID-19 and the associated lockdown restrictions may have competed with non-COVID-19 related booster vaccine delivery. In the Ardennes region, COVID-19 vaccination was well respected by the population with 93.5% of 25 to 29-year-olds being fully vaccinated [15]. Conversely, vaccination against COVID-19 in people over 18 years old on May 12, 2021 may have provided an opportunity for 25-year-olds to receive the dTcaP booster, therefore, increasing dTcaP vaccination coverage before the study period. Among those aged 25 years in 2020 residing in the region in June 2021, 25.6% received a dTcaP booster vaccine in the previous year. However, the number of those vaccinated during the study period was lower (16.7%).

As a health insurer, the CPAM is not entirely recognized among the French population for its preventive approaches, therefore, the awareness campaign may not have corresponded to the expectations of the participants. Some participants may not have paid sufficient attention to the information disseminated in the awareness campaign. In 2020, Plichon et al. studied the impact of the framing of a message and the arguments presented to explain changes in attitude towards vaccinations, intention to be vaccinated or to recommend a vaccination to relatives [16]. Their study was carried out with young adults aged 18 to 25 years and showed that the formulation of a message from a punitive point-of-view (non-vaccination is illegal) did not increase the intention of participants wanting to be vaccinated, whereas a positive message formulation (being vaccinated respects the law) led to a feeling of being protected by the law and a positive change was reported in the attitude towards vaccination as well as stronger intention for participants to be vaccinated. The wording of the information provided in the CPAM campaign was phrased in a gain-altruistic way and highlighted that being vaccinated protects one’s health and that of others. We surmised that a shorter or legally oriented formulation may have had a greater impact. It is also possible that participants in this study did not feel concerned by the generic and impersonal message provided.

The rate of vaccinated adults during the study period was low (16.7%). Over the last few years, vaccine hesitancy associated with negative feelings about the safety of vaccines has developed in France. According to Larson et al., in 2016 among 67 countries, 45.2% of the French population were skeptical about vaccine safety [17]. However, in the Vaccine Confidence Project, the latest analysis dating from 2020 and carried out in 27 European Union countries and the UK showed that slightly over half of the French population surveyed (51%) had overall confidence in vaccines (COVID-19 vaccinations excluded) [18].

Consultations with a GP was significantly associated with the uptake of the dTcaP booster vaccine. Patients recognize GPs as providers of credible information and they play a key role in individualized preventive healthcare actions, in which their influence on the acceptance of vaccines in children has already been shown [19, 20]. In 2004, Beytout et al. discussed the possibility of creating a specific GP appointment at fixed ages in order to allow both GPs and the general population to be up to date with vaccinations in France [10]. This was taken up by the French Minister of Health on September 19, 2022 in a bill covering the financing of national health insurance programs. Moreover, Goodwin et al. showed an increase in participation in colorectal cancer screening when an invitation letter was signed by a GP [21]. Therefore, one way of improving dTcaP vaccination coverage for 25-year-olds who participated in our study could be for the CPAM and GPs to work together. Multiple studies such as Blank et al. (2008) show that a recommendation from a healthcare provider is the most important driver to increase vaccination uptake [22]. Moreover, a survey in Ireland conducted by Giese et al., in 2013, identified that influenza vaccination was associated with a GP vaccination recommendation [23].

Regarding the strengths and limitations of this study, the originality of testing the impact of an awareness campaign on a large population via a randomized methodology posed a strength. However, we did not directly question the participants to identify the reasons why participants did not have the booster vaccine in the follow-up. For the INT group, we were unable to ascertain if information from the CPAM campaign was actually received and read, nor to assess their satisfaction with its content. The absence of an individual data collection on participants’ follow-up and healthcare pathways also did not allow us to take into consideration any possible confounding factors such as the professional setting (where some may have received a vaccination through an occupational medicine specialist), or to identify a routine follow-up provided by the GP.