A pre-visit app and HPV vaccine uptake: promising, and very small

Design

Pilot two-arm randomised controlled trial with nested qualitative interviews; attention control

Population

57 parents of unvaccinated adolescents aged 9-17 at two urban clinics in Tennessee, USA

Primary outcome

Feasibility and acceptability, with HPV vaccine initiation from electronic records at 12 months as preliminary efficacy

Effect

Initiation 48% (intervention) vs 17% (control); difference 0.24 (95% CI 0.03-0.46), P=.01; knowledge and concern score differences not significant (P=.13 and P=.14)

Parents arrive at the clinic with their questions about HPV vaccination already formed, and the consultation is often too short to reach them. This pilot randomised 57 parents of unvaccinated 9- to 17-year-olds at two urban clinics in Tennessee to a tailored web app delivered before the visit, or to nutrition education as an attention control. Providers were blinded; parents could work out which arm they were in.

Four-fifths of those offered the app used it. HPV vaccine initiation, taken from the electronic record twelve months later, was 48% in the app arm against 17% in the control arm (difference 0.24, 95% CI 0.03-0.46, P=.01). The measures the app was designed to move — knowledge and concern scores — both shifted further in the intervention arm but neither difference reached significance.

That combination should temper enthusiasm rather than raise it: the mechanism did not separate while the outcome did, in 57 people. What the qualitative work adds is more durable than the trial arithmetic. Parents described the app as confirming a decision they had already leaned towards, helping them talk to their child, and giving them questions to bring to the clinician. Those are the functions worth designing for, in whatever form a given clinic can deliver.

• Treat the effect size as a pilot signal, not an estimate
• The usable insight is timing: parents' questions are formed before the consultation begins
• Written or digital material must be in the language the family reads — English-only was a stated barrier here
• Prompting parents to bring questions may matter as much as the content given
• Record vaccination status at every adolescent contact, whatever the visit was for

Why it matters

It locates the decision point outside the consultation, where most vaccine communication effort is currently not spent.

Don't overread it

This was a pilot in 57 mostly non-Hispanic White, English-speaking parents at two US clinics; the uptake figure is not an estimate that transfers.

The statistics, in plain English

With 27 and 30 participants, a difference between 48% and 17% rests on a handful of children, and the confidence interval (0.03 to 0.46) reflects that: the true difference could be almost nothing or very large. A pilot is designed to test whether a trial is feasible, not to measure an effect, and the secondary measures failing to separate is the expected result at this size rather than a contradiction.

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