Web-Based Tailored Messaging to Increase Vaccination: A Randomized Clinical Trial

"Given that vaccine hesitancy remains a significant public health issue..., researchers should continue to develop and test communication approaches to reduce parental vaccination concerns and improve the timely uptake of infant immunizations."

In light of the multiple determinants of vaccination decisions, one approach to vaccine hesitancy is message tailoring, which involves crafting messages to address each person's attitudes, beliefs, experiences, knowledge, and values. Conducted between April 2016 and June 2019, this randomised clinical trial (RCT) tested the effectiveness of Vaccines and Your Baby (VAYB), a Web-based tailored messaging intervention designed to increase the timely uptake of childhood vaccinations in the United States (US).

For the RCT, 824 pregnant women and new parents were randomly assigned to one of three arms:

1. VAYB (276 women), which provided new parents with vaccine information messages tailored to vaccine beliefs and values. The intervention is detailed at Related Summaries, below, but, in short, VAYB was based on a hybrid of the theory of planned behaviour and the values-attitude-behaviour model, combined with approaches from motivational interviewing and persuasive messaging. Led by a multidisciplinary team and developed with an iterative and user-centred approach, the VAYB website featured messages that addressed each participant's vaccination attitudes and concerns, framed according to personal values (e.g., acknowledging their desire to "keep their child safe"). Tailored messages used empathetic language and emphasised autonomy to affirm individual values. The intervention and surveys were administered again when the child was age 4 to 6, 10 to 12, and 13 to 15 months. The website was retailored and refreshed at each time point on the basis of updated parent vaccine values survey responses.
2. An untailored (UT) version of the intervention (276 women), which had the same design and factual information as the VAYB website but was not personalised to the participants' survey responses, and the content did not change across the time points.
3. Usual care (UC; 274 women), which consists of scheduled 20-minute well-child visits at 2, 4, 6, and 12 months of age, with an option for a 9-month visit. Recommended childhood immunisations are administered at these health supervision visits, and it is standard practice to offer parents vaccine information statements relevant to that visit.

Participants in the UT and UC arms were administered the same surveys at the 4 intervention time points as those received by participants in the VAYB arm. The primary outcome was up-to-date status for recommended vaccines from birth to 200 days of age. A modified intent-to-treat analysis was conducted. In brief, the researchers found:

• There were up-to-date vaccination rates of 91.44%, 92.86%, and 92.31% in the VAYB, UT, and UC arms, respectively; differences were not statistically significant.
• In the subanalysis stratified by vaccine hesitancy status (14% of the study participants were classified as vaccine hesitant at baseline), infants of vaccine-hesitant parents in the VAYB arm were less likely to be up to date than infants of vaccine-hesitant parents in the UT arm (odds ratio (OR) = 0.28; 95% confidence interval (CI), 0.08-0.98).
• The likelihood of being up to date on vaccinations was no higher for infants in the VAYB arm than those in the UC arm (OR 0.89; 95% CI, 0.45-1.76) or the UT arm (OR 0.82; 95% CI, 0.42 to 1.63).
• There was no difference between the UT and UC arms in the likelihood of being up to date (OR 1.08; 95% CI, 0.54-2.18).

Thus, this RCT suggests that Web-based tailored messaging does not positively impact parental immunisation behaviours during infancy. The researchers consider several explanations for the findings, such as the fact that the intervention might have been effective if it had been implemented in other healthcare environments with lower infant vaccination rates and higher rates of vaccine hesitancy. Also, while they designed the intervention to tailor messages on both vaccine values and attitudes, it is possible that for some participants, the tailored content was on target for one construct but off target for the other construct.