Discussion
FLU, INFLUENZA
We explored the effects of a behaviourally-informed letter on uptake of childhood influenza vaccination in general practices, and of a letter and a reminder (SMS/email) on uptake at schools. The behaviourally-informed, centrally sent invitation letter increased the proportion of children who received a vaccination at their general practice in absolute terms by 13.7% (from 23.4 to 37.1%). The effect of the invitation letter remained significant after adjusting for demographic variables and interaction effects, with children in the intervention group being more likely to be vaccinated than the control, OR = 2.17, The effect of the interventions in schools was much smaller, though still statistically significant, with uptake ranging from 61.6% of the school year in the control group, who received the standard invitation letter and no reminder, to 63.5% in the group who received the standard letter and a reminder, an increase of almost 2% in absolute terms. In a fully adjusted model receiving a reminder had a statistically significant effect on vaccine uptake, Our behaviourally-informed letter increased uptake of the flu vaccine in general practice but it did not increase uptake in schools. In both studies, the control groups received usual practice. In the schools study, there was a standard letter invitation letter sent to all parents from the provider. In the general practice study, control practices and intervention practices may have sent parents an invitation letter, issued an opportunistic invitation, or not sent an invitation at all directly. GPs are contracted to call and recall for flu vaccinations. The National Institute of Health and Care Excellence (NICE) recommends contacting people for immunisations by a variety of methods, including text messages, letters, emails, phone calls from staff or an auto dialler, social media, or a combination of methods, as well as informing and inviting people during face-to-face interactions whenever the opportunity arises [There were some differences between the behavioural letter in the general practice and the schools study. The schools letter did not use personalisation, as that could not be implemented; nor was there was a tear off slip for an appointment, since the action was to complete and return the consent form. The schools letter had a positive social norms statement that was not in the GP letter. Since these differences between the letters are confounded with the difference in controls, we cannot be completely sure that the difference in effectiveness was due to the control (receipt of a letter invitation vs usual practice) or due to the differences in the letter (personalisation vs than norms).Another difference between the GP and the schools trials is that the school-based programme sends a leaflet with the invitation letter, which has information about side-effects. In the behaviourally-informed letters, we did not address concerns about the vaccine’s effectiveness and side-effects, which have been shown to cause influenza vaccine hesitancy in parents [In an intention-to-treat analysis, our reminder led to a small increase in the proportion of children being vaccinated in schools, at the cost of an additional workload for schools. We collected data on fidelity to the study protocol in Dorset and the fidelity was poor: the providers did not necessarily use the wording that we gave them. We also found that a lot of the control schools were sending out reminders. We expect that the reminder would have increased uptake by increasing the return of consent forms; we found that both the letter and the reminder increased the number of consent forms returned (with no interaction effect), with increases in the proportion of forms returned of up to 2.6% in the reminder only condition compared to the control, taking the percentage for forms returned up to 76%. But there were still ~ 25% of parents who were not returning the consent forms in each condition, which suggests that there may be further scope for interventions that target the return of consent forms, especially given that 92.7% of people in the UK agree that vaccines are important for children to have [Further, we found that the proportion of forms returned with consent refused increased when the intervention letter was sent, with increases of up to 1.6% in the letter only condition, taking refusals up to 10%. While reminders can be effective for parents who want their child to be vaccinated but do not get around to it [This could also be an explanation for why our GP trial had larger effects. The baseline uptake rate in schools is higher than in general practice, so the interventions in schools are more likely to have been subject to a ceiling effect. The difference in baseline uptake rate is not surprising. The two settings target children of different ages, with the school children being older than those vaccinated in general practice, and data suggests that vaccine uptake decreases as age increases [Across all groups in the school study, we found that uptake of the vaccination decreased with the percentage of children in the school who were eligible for school meals, In the general practice study, children who had been vaccinated the previous year were more likely to be vaccinated, OR = 3.83, In the general practice study, we found variation between practices and CCGs, and in the school study we found variation between both school years and schools, suggesting that there are practice/school level factors that influence uptake. The CCG-level differences are consistent with other data, which shows that uptake of the flu vaccine for 2- to 3-year olds varies from 19 to 61% across CCGs [