JMIR Publications

ABSTRACT

Background:

In the Netherlands, HPV vaccination uptake remains low. To improve informed decision making (IDM) and HPV vaccination acceptability, we systematically developed an interactive, Web-based tailored intervention for mothers of Dutch girls to-be-invited.

Objective:

The aim of this study is to provide insight into the intervention’s working mechanisms by evaluating (1) program use, (2) program acceptability, and (3) the relationship of program use with (a) program acceptability, and (b) intervention effects (i.e., dose-response).

Methods:

Only mothers from the intervention arm of a randomized controlled study (RCT) that assessed the effectiveness of the Web-based, tailored intervention were included. They were invited to visit the Web-based intervention between baseline (January 2015, just before access to the intervention) and follow-up (March 2015, prior to the first HPV vaccination). Indicators for program use were time of website use (i.e., duration of intervention exposure) and completeness (i.e., the proportion of all available webpages visited). HPV vaccination uptake registered by Praeventis was used as the primary outcome. Secondary outcomes were informed decision-making (IDM), decisional conflict, and social psychological determinants of HPV vaccination uptake.

Results:

From the 3995 invited mothers, 2509 mothers (62.80%) logged in. Of these, 2239 mothers (89.24%) visited at least one page of the intervention components. On average, mothers spent 21.39 minutes on the website (SD = 12.41 minutes) and completed 50.04% (SD = 26.18%) of the website. Participants rated the website with a 7.64 on a 10-point scale (SD = 1.39). Program acceptability was significantly associated with completeness (β = 4.36, P < .001), but not with time of website use (β = -.07, P =.77). Intention-to-treat analysis (N = 3,995) showed a significant positive effect of completeness on all outcome measures (P’s <.003; Bonferroni corrected alpha=.05/15 factors), including on HPV vaccination uptake. Time of website use had a significant positive effect on all outcomes (P’s <.003), except for uptake (P = .195), risk perception when not vaccinated (P = .144), subjective norms (P = .032), and habit (P = .013).

Conclusions:

Program use and acceptability of the intervention was adequate. Completeness was positively associated with acceptability. Furthermore, positive effects (i.e., dose-response effects) were found of completeness and time of website use on the mothers IDM, decisional conflict, and almost all of the social-psychological determinants of HPV vaccination acceptability. In addition, the extent to which mothers completed the intervention had a positive impact on their daughters’ vaccination uptake. This indicates that the Web-based, tailored intervention fits well with the mothers’ needs, and that completeness of use is essential for improving HPV vaccination uptake, acceptability, and IDM. Program use should therefore be promoted. Clinical Trial: Trial Registration: Trialregister.nl NTR4795; https://www.trialregister.nl/trial/4795