Countering Vaccine Hesitancy among Pregnant Women in England: The Case of Boostrix-IPV

"...pregnant women have been found to be more vaccine hesitant than the general population..."

In response to a national outbreak of whooping cough in the United Kingdom (UK), a vaccine with low-dose diphtheria, tetanus, acellular pertussis, and inactivated poliomyelitis (Boostrix-IPV or DTaP/IPV) for pregnant women was introduced in October 2012. In light of the fact that coverage of Boostrix-IPV in England is suboptimal and declining (69%), this study explored whether the manner in which vaccine information is framed could impact vaccine acceptability and uptake. It also assessed whether constructs from the Theory of Planned Behaviour (TPB) - attitudes, subjective norms, perceived behavioural control (PBC), and intentions - were associated with antenatal vaccine intentions and behaviours for Boostrix-IPV. Finally, the study evaluated the association between framing effects and background factors, including education level, number of children, and vaccine history.

Data for the study, which employed a cross-sectional between-subjects design, were collected between May and July 2017 inclusive. In the disease risk condition, participants read a short story about a baby who contracted whooping cough, which highlighted the health risks posed by failing to vaccinate. In the myth busting condition, participants read that some pregnant women have safety concerns about the vaccine. They were then presented with a summary of three studies that refuted the link between vaccinating while pregnant and adverse outcomes for the mother and baby. In the control condition, participants read a vignette on an unrelated scientific topic (bird feeding). Ninety-seven participants were randomly assigned to the disease risk condition, 98 to the myth busting condition, and 87 to the control condition - for a total sample size of 282 participants.

Contrary to this study's hypothesis and previous findings, no statistically significant differences were found across the three conditions in attitudes, PBC, subjective norms, or intentions. All between-group differences remained non-significant. Furthermore, mean intention scores were very high across all three conditions, with more than 80% of participants reporting that they were "very likely" to receive the vaccine.

In seeking to understand the findings, the researchers note that 97% of participants were aware of the vaccine prior to the study. Given that all respondents were at least 16 weeks pregnant, this may be as a result of a recent healthcare consultation. Thus, it is possible that brief framing messages, such as those examined in the current study, are ineffective in altering vaccine attitudes among informed message recipients. These findings raise questions for future research to address, given that the majority of message framing studies have not assessed participants' prior vaccine-related knowledge. Also, the effects of framing may be moderated by whether the advocated health behaviour is vaccination of the message recipient (i.e., mother) or vaccination of an individual for whom the recipient is responsible (i.e., baby/child).

Participants were active online pregnancy support group members and other social media users who volunteered to partake in vaccine research after being offered only a small incentive to do so. Future studies may benefit from recruiting participants from a diverse range of online platforms or settings.

The TPB was found to be a good fit for the data, with TPB constructs predicting 86% of the variance in vaccine intentions. Participants with more positive vaccine attitudes and those who perceived higher levels of approval from close family and friends showed stronger intentions to receive the antenatal vaccine. Thus, the results provided preliminary evidence that constructs from the TPB may be suitable targets for interventions aimed at reducing antenatal vaccine hesitancy.

The researchers conclude that further research is needed to determine effective strategies to increase informed uptake in pregnant women. This cohort is an accessible population and is regularly exposed to healthcare information through routine antenatal care. Pregnant women are also candidates for an increasing number of vaccines. Hence, effective strategies for increasing uptake of Boostrix-IPV may provide useful insights for other antenatal vaccines.