Neighborhood determinants of 2009 pandemic A/H1N1 influenza vaccination in Montreal, Quebec, Canada

Abstract

Neighborhood-level analyses of influenza vaccination can identify the characteristics of vulnerable neighborhoods, which can inform public health strategy for future pandemics. In this study, the authors analyzed rates of 2009 pandemic A/H1N1 influenza vaccination in Montreal, Quebec, Canada, using individual-level vaccination records from a vaccination registry with census, survey, and administrative data to estimate the population at risk. The neighborhood socioeconomic and demographic determinants of vaccination were identified using Bayesian ecologic logistic regression, with random effects to account for spatial autocorrelation. A total of 918,773 (49.9%) Montreal residents were vaccinated against pandemic A/H1N1 influenza from October 22, 2009, through April 8, 2010. Coverage was greatest among females, children under age 5 years, and health-care workers. Neighborhood vaccine coverage ranged from 33.6% to 71.0%. Neighborhoods with high percentages of immigrants (per 5% increase, odds ratio = 0.90, 95% credible interval: 0.86, 0.95) and material deprivation (per 1-unit increase in deprivation score, odds ratio = 0.93, 95% credible interval: 0.88, 0.98) had lower vaccine coverage. Half of the Montreal population was vaccinated; however, considerable heterogeneity in coverage was observed between neighborhoods and subgroups. In future vaccination campaigns, neighborhoods that are materially deprived or have high percentages of immigrants may benefit from focused interventions.

Figure 1.

Distribution of vaccinations in Montreal, Quebec, Canada, during the 2009 pandemic A/H1N1 influenza outbreak, and vaccinations among Montreal residents included in the current study, October 2009–April 2010.

Figure 2.

Cumulative pandemic A/H1N1 influenza vaccine coverage in Montreal, Quebec, Canada, from October 22, 2009, to December 31, 2009, among A) designated priority groups and B) different age groups, by date of vaccination. Vertical bars indicate vaccination eligibility dates (see Web Table 1). Part A (priority groups): long-dashed line, health-care workers; solid line, pregnant women; medium-dashed line, chronically ill persons aged <65 years. Part B (age groups): long-dashed line, age 6 months–4 years; short-dashed line, age 5–19 years; solid line, age 20–64 years; medium-dashed line, age ≥65 years.

Figure 3.

Box plots of neighborhood (n = 111) pandemic A/H1N1 influenza vaccine coverage in Montreal, Quebec, Canada, by characteristic, October 2009–April 2010. Neighborhoods with greater than 100% coverage (1 neighborhood for 5- to 19-year-olds, 1 neighborhood for pregnant women, and 5 neighborhoods for health-care workers) were coded as having 100% coverage. The lines of the box represent the first quartile (Q1), the median value (Q2), and the third quartile (Q3). The box spans the interquartile range (IQR; Q3 − Q1). The whiskers (the 2 outermost horizontal lines) represent the lower bound (1.5(IQR) − Q1) and the upper bound (1.5(IQR) + Q3). The dots are outliers (data points outside the upper/lower bounds).

Figure 4.

Choropleth maps of neighborhood pandemic A/H1N1 influenza vaccine coverage in Montreal, Quebec, Canada, among A) the total population, B) pregnant women, C) chronically ill persons under age 65 years, and D) health-care workers, October 2009–April 2010. Neighborhoods with greater than 100% coverage (1 neighborhood for pregnant women and 5 neighborhoods for health-care workers) were coded as having 100% coverage.

Figure 5.

Choropleth maps of neighborhood variables included in an analysis of pandemic A/H1N1 influenza vaccination in Montreal, Quebec, Canada, 2006. A) Material deprivation; B) social deprivation; C) percentage of immigrants. For indices of deprivation, see Pampalon and Raymond (43).