Effect and Cost-Effectiveness of Educating Mothers about Childhood DPT Vaccination on Immunisation Uptake, Knowledge, and Perceptions in Uttar Pradesh, India: A Randomised Controlled Trial

"These findings contribute to a growing body of evidence on what are the most effective strategies to improve vaccination rates in developing countries."

This study reports findings from a randomised controlled trial (RCT) in India that examined the extent to which health information messages designed to educate mothers on the benefits of the combined diphtheria-pertussis-tetanus (DPT) vaccine increased immunisation coverage, and whether the framing of the information has implications for outcomes.

The RCT was conducted in 180 villages (clusters) across 6 districts of Uttar Pradesh, an Indian state where only 51% of children aged 12-23 months are fully immunised. Potential reasons for inadequate levels of immunisation coverage include problems in the supply of vaccines as well as demand-side factors such as time costs, high discount rates, distrust, fear, and limited knowledge. If parents underestimate the true efficacy of vaccines or are simply unaware of their existence, it is plausible that providing information could increase uptake of vaccinations. There is reason to believe that parents may be poorly informed as to the benefits of immunisation. Female literacy is far from universal in many in low- and middle-income countries (LMICs), and information problems are likely to be pervasive.

The study, involving 722 mothers of children aged 0 to 36 months, tested an information intervention that was informed by the theory behind framing, previous research on framing in health, and extensive piloting. Field staff were mostly male, had completed secondary school, and were from the same state but were not known to the communities. The information was delivered to mothers face-to-face in the privacy of their home, and field staff followed a script that they were trained to deliver in a standardised manner. There were 2 versions of the script: (i) the first framed the information on tetanus vaccination as gains - e.g., the child is less likely to get tetanus and more likely to be healthy if vaccinated; and (ii) the second framed information on tetanus vaccination as a loss - e.g., the child is more likely to get tetanus and suffer ill health if not vaccinated. Both variants of the intervention informed mothers where in the public sector they could get their child vaccinated. Visual aids were used to help convey the information in an accessible manner to illiterate women, and a Hindi leaflet containing the information was left with the mother. A short question-and-answer session followed the provision of the information. The intervention took about 10 minutes to deliver.

Data were collected at baseline in September 2015 and 7 months later at endline in April 2016. Participants were randomly assigned to 1 of the 3 treatment groups: information positively framed (n = 237), information negatively framed (n = 246), or no information (n = 239). A total of 16 (2.2%) participants were lost to follow-up, resulting in a final analytical sample of 706. The pre-specified primary outcome was the proportion of children who had received DPT3 measured after 7 months of follow-up. Pre-specified secondary outcomes were the proportion of children fully vaccinated against tuberculosis, diphtheria, pertussis, tetanus, and measles; the mother's knowledge of any symptom of tetanus; and the mother's perception of the efficacy of tetanus vaccination.

The proportion of children with DPT3 was 28% in the control group and 43% in the 2 groups receiving information, giving a difference of 14.6 percentage points (95% confidence interval (CI): 7.3 to 21.9, p < 0.001) and a relative risk of 1.5 (95% CI: 1.2 to 1.9, p < 0.001). In other words, children whose mothers received the information were 52% more likely to receive DPT3 than children in the control group.

Results for the secondary outcomes follow a similar pattern. The effect of the information intervention on the proportion of children fully immunised was an increase of 14 percentage points (95% CI: 7.7 to 21.1, p < 0.001), equivalent to a relative risk of 1.7 (95% CI: 1.3 to 2.3, p < 0.001). Despite the information never mentioning measles, the effect on measles coverage was 22 percentage points (95% CI: 14.3 to 29.6, p < 0.001). Looking across all the secondary outcomes, the framing of information had no effect, with the exception of knowledge of prevention.

The researchers conducted several additional analyses to better understand the main findings, learning that: (i) The intervention had a significant positive effect on mothers who, at baseline, believed the DPT vaccine to have an efficacy level below 50% (difference: 0.88, 95% CI: 0.06 to 1.69, p = 0.04). The intervention did not have an effect on mothers who were already convinced of the efficacy of the DPT vaccine - i.e., those who had perceptions of efficacy above 50% at baseline (difference: 0.01, 95% CI: -0.36 to 0.37, p = 0.97). (ii) Using variation in the geographical density of study households assigned to the information intervention, they found no evidence of spillovers. That is, proximity to study households that received the information intervention did not affect the probability of children receiving DPT.

The total cost of the information intervention was US$11,353, and the cost per disability-adjusted life year (DALY) averted was US$186, making the intervention highly cost-effective. The researchers explore potential suggestions for even cheaper implementation:

• The findings leave open the possibility that the intervention worked through various channels, one being that the information served simply to remind mothers to get their child vaccinated. Some might say, then, that cheaper interventions, such as short messaging service (SMS) text message reminders, could be implemented. They caution against such an interpretation - for one thing, arguing that studies of the effect of text message reminders on vaccination uptake in developing countries have produced mixed results.
• One could engage Accredited Social Health Activists (ASHAs), given that they are integral to the delivery of community health services and have a strong focus on maternal and child health. A potential concern would be the loss of fidelity in the implementation of the intervention. At the same time, the messages are simple and quick to deliver.
• There is a growing literature on social networks being exploited to spread information and behaviours, e.g., by targeting highly connected individuals, nominated friends of individuals, or community leaders.

In discussing the findings, the researchers make some further observations:

1. Providing mothers of unvaccinated or incompletely vaccinated children with information on tetanus and the benefits of vaccination substantially increased immunisation coverage of DPT3, full immunisation, and measles. The large effect on measles vaccination was not anticipated, given that the information intervention focused solely on tetanus. They speculate that the increase in measles vaccination was generated by increased engagement with the public health system and, in turn, health workers ensuring children were up to date on all their vaccines, not just DPT3.
2. Although the effects of negative framing were consistently larger than when information was framed as a gain, differences between the 2 groups were small and rarely significant. In light of these results, "a prudent strategy would be to adopt the negative framing of the information script since there are no cost implications."
3. Information improved mothers' knowledge of causes of, symptoms of, and methods of prevention against tetanus. There was no effect on perceptions of vaccine efficacy, but there was suggestive evidence of an increase in perceptions of efficacy for mothers who initially had inaccurate perceptions.

The researchers highlight a number of context-specific factors that may be relevant when considering the wider relevance of the findings: (i) The 6 study districts were not the worst performing in the state. In areas where immunisation rates are lower, the intervention might produce larger effects. (ii) A local organisation implemented the intervention; however, any future scale-up would likely rely on government delivery channels, which may reduce costs but at the same time could present risks in terms of implementation fidelity. (iii) Mothers' knowledge and perceptions of efficacy at baseline were quite low; the intervention is likely to be less effective in areas where awareness and knowledge levels are higher. (iv) The supply of vaccines must be in place, at least intermittently, if information is to have any effect in increasing immunisation rates.

In conclusion, the "results demonstrate that targeted and clear information delivered to mothers of unvaccinated/incompletely vaccinated children can be effective in improving immunisation coverage....Although the barriers to immunisation uptake are multiple, ranging from social norms to the reliability of supply systems, in contexts where knowledge and awareness are a key binding constraint, interventions that provide information to parents and carers of unvaccinated children have the potential to be a simple and cost-effective way of increasing demand for immunisation."