Does education about local vaccination rates and the importance of herd immunity change US parents' concern about measles?

Abstract

It is unclear how broadly aware parents are of the concept of herd immunity and whether parents consider community benefits of vaccination when making decisions about their child's vaccinations. We aimed to determine whether educating parents about community-level benefits of measles, mumps, and rubella (MMR) vaccination and local vaccination rates would impact concern about their child's risk of measles and risk of a measles outbreak. We conducted an electronic survey among Minnesota parents of children aged 6-18 years in August 2016. We assessed baseline knowledge of herd immunity, asked participants to estimate MMR vaccination coverage in their county, and asked participants to estimate the minimum coverage needed to prevent measles outbreaks. We then delivered a short, educational intervention via the survey to inform participants about the benefits of herd immunity, the actual MMR vaccination coverage in their county, and that at least 95% MMR vaccination coverage is needed to prevent measles outbreaks. Pre- and post-intervention, participants were asked to report how concerned they were that their child might get measles. We used logistic regression models to assess factors associated with awareness of herd immunity, change in concern about one's child's measles risk, and overall concern for a measles outbreak. Among 493 participants, 67.8% were aware of herd immunity at baseline. Post-intervention, 40.2% (n = 198) of parents learned that MMR vaccination rates in their county were higher than they expected. All participants found out that their county MMR rates were lower than the measles herd immunity threshold of 95%. Overall, 27.0% (n = 133) of participants reported an increase in concern that their child might get measles after learning about local vaccination coverage and the coverage needed to achieve herd immunity. We found that our short, educational intervention aimed to increase awareness about herd immunity and local vaccination led to an increase in concern about disease risk among less than a third of parents.

Keywords: Herd immunity; Indirect protection; MMR vaccination; Measles; Vaccination coverage.

Fig. 1.

Summary of the survey intervention designed to address the aims of this study and the timing at which they were delivered during the survey. Participants were asked questions and then provided with educational information to increase knowledge about the concept of herd immunity, the MMR vaccination coverage in their county, and the herd immunity threshold for measles.

Fig. 2.

Adjusted odds ratio and 95% confidence intervals for the association between each demographic covariate, perception of concern about measles, and awareness of herd immunity as estimated from a multivariate logistic regression model.

Fig. 3.

Adjusted odds ratio and 95% confidence intervals for the association between each demographic covariate, awareness of herd immunity, perception of concern about measles, and increase in concern about one’s child’s risk of measles post-intervention as estimated from a multivariate logistic regression model.

Fig. 4.

Adjusted odds ratio and 95% confidence intervals for the association between each covariate, awareness of herd immunity, perception of concern about measles, and an individual’s concern that their county is at risk for a measles outbreak as estimated from a multivariate logistic regression model.

Fig. 5.

The dark grey bars represent the proportion of participants who underestimated MMR vaccine coverage in their county of residence, the grey bars represent the proportion of participant who correctly estimated the MMR vaccine coverage in their county of residence, within five percentage points, and the light grey bars represent the proportion of participants who overestimated MMR coverage in their county of residence. Comparisons of MMR coverage per county were made based on the MDH MIIC report as of January 1, 2016. Only those counties that comprised more than 80% of the sample are displayed.

Fig. 6.

Sankey plots depicting the proportion of respondents reporting each degree of concern that their child’s measles risk (colored lines), both before receiving any information regarding the local MMR vaccine coverage or the herd immunity threshold (“Pre %”) and after receiving this information (“Post %”).