Delayed Measles Vaccination of Toddlers in Canada: Associated Socio-demographic Factors and Parental Knowledge, Attitudes and Beliefs

"Vaccine hesitancy and its contribution to vaccination delays should be further studied."

Delaying childhood vaccines extends the period of vulnerability of children to vaccine-preventable diseases (VPDs) and is a predictor for an incomplete vaccination status at a later age. This study used data from the 2013 Childhood National Immunization Coverage Survey (cNICS 2013) to examine the distribution of delays in the uptake of the first dose of measles vaccine in 2-year-old children in Canada, and to explore socio-demographic factors and knowledge, attitudes, and beliefs (KAB) associated with delayed measles vaccination in this age group. The researchers explain that associations between parental KAB and vaccination delays may indicate vaccine hesitancy.

The analyses were carried out on a sample of 3,604 two-year-old children. Logistic regression was used to examine sociodemographic factors and KAB associated with the 2 outcomes of interest: delays of 1-6 months (vaccination at 13 to 18 months of age) and delays of 7-18 months (vaccination at 19 to 23 months of age). Overall, 69% (95% confidence interval (CI) 67-71) of children received their first valid dose on time. Twenty-nine percent (95% CI 27-31) and 11% (95% CI 9-12) of children were unvaccinated before turning 13 and 16 months of age, respectively. Factors associated with delays of 1-6 months were being a girl, being born outside Canada, and the jurisdiction of residence. Being from a single-parent family, being born outside Canada, and the jurisdiction of residence were associated with delays of 7-18 months, suggesting that potential barriers might be at play.

Some KAB were associated with vaccination delays as depicted in Table 4 in the paper. Not believing that childhood vaccines are safe had the strongest and the most statistically significant association (odds ratio (OR) 0.48, 95% CI 0.26-0.87) with vaccination delays of 1-6 months. Confidence in the safety of childhood vaccines was also inversely associated with 7- to 18-month delays (OR 0.29, 95% CI 0.09-0.91). Among the factors statistically associated with these delays, agreeing with alternative practices for replacing vaccination presented the strongest association (OR 3.60, 95% CI 1.77-7.33). Parents believing that alternative practices such as homeopathy or chiropractic could replace vaccination were thus more than 3 times more likely to delay their child's measles vaccine 7-18 months, compared to parents disagreeing with these practices. This association was also found to 1- to 6-month delays (OR 1.45, 95% CI 1.03-2.05). Parents feeling they had enough information about vaccination were less susceptible to delay their child's vaccine 7-18 months compared to parents who were voicing a need for more information (OR 0.42, 95% CI 0.22-0.81). Finally, expressing concerns regarding measles, mumps, and rubella (MMR) safety was marginally associated with 7- to 18-month delays, although this association did not reach statistical significance (OR 1.82, 95% CI 0.99-3.35).

The researchers reflect on these findings, citing, for example, the "Three Cs" model proposed by a World Health Organization (WHO) working group, which states that vaccine hesitancy is influenced by factors that can be grouped into 3 broad categories: complacency, confidence, and convenience. The perceived lack of information identified as a factor associated with delays could be linked to health literacy and thus not be a facilitating element in the decision of giving one's child their vaccine.