Impact of H1N1 on socially disadvantaged populations: systematic review

Abstract

Background: The burden of H1N1 among socially disadvantaged populations is unclear. We aimed to synthesize hospitalization, severe illness, and mortality data associated with pandemic A/H1N1/2009 among socially disadvantaged populations.

Methods/principal findings: Studies were identified through searching MEDLINE, EMBASE, scanning reference lists, and contacting experts. Studies reporting hospitalization, severe illness, and mortality attributable to laboratory-confirmed 2009 H1N1 pandemic among socially disadvantaged populations (e.g., ethnic minorities, low-income or lower-middle-income economy countries [LIC/LMIC]) were included. Two independent reviewers conducted screening, data abstraction, and quality appraisal (Newcastle Ottawa Scale). Random effects meta-analysis was conducted using SAS and Review Manager.

Conclusions/significance: Sixty-two studies including 44,777 patients were included after screening 787 citations and 164 full-text articles. The prevalence of hospitalization for H1N1 ranged from 17-87% in high-income economy countries (HIC) and 11-45% in LIC/LMIC. Of those hospitalized, the prevalence of intensive care unit (ICU) admission and mortality was 6-76% and 1-25% in HIC; and 30% and 8-15%, in LIC/LMIC, respectively. There were significantly more hospitalizations among ethnic minorities versus non-ethnic minorities in two studies conducted in North America (1,313 patients, OR 2.26 [95% CI: 1.53-3.32]). There were no differences in ICU admissions (n = 8 studies, 15,352 patients, OR 0.84 [0.69-1.02]) or deaths (n = 6 studies, 14,757 patients, OR 0.85 [95% CI: 0.73-1.01]) among hospitalized patients in HIC. Sub-group analysis indicated that the meta-analysis results were not likely affected by confounding. Overall, the prevalence of hospitalization, severe illness, and mortality due to H1N1 was high for ethnic minorities in HIC and individuals from LIC/LMIC. However, our results suggest that there were little differences in the proportion of hospitalization, severe illness, and mortality between ethnic minorities and non-ethnic minorities living in HIC.

Figure 1. Study flow.

This is the flow of citations and articles that were screened for the systematic review.

Figure 2. Meta-analysis of hospitalizations among ethnic minorities versus non-ethnic minorities in North America.

Favours ethnic minority means that ethnic minorities experienced a lower proportion of H1N1 hospitalizations compared to non-ethnic minorities. Favours non-ethnic minorities means that non-ethnic minorities experienced a lower proportion of H1N1 hospitalizations compared to ethnic minorities.

Figure 3. Meta-analysis of ICU admissions among ethnic minorities versus non-ethnic minorities.

Favours ethnic minority means that ethnic minorities experienced a lower proportion of intensive care unit (ICU) admissions due to H1N1 compared to non-ethnic minorities. Favours non-ethnic minorities means that non-ethnic minorities experienced a lower proportion of ICU admissions due to H1N1 compared to ethnic minorities.

Figure 4. Meta-analysis of mortality among hospitalized ethnic minorities versus hospitalized non-ethnic minorities.

Favours ethnic minority means that ethnic minorities experienced a lower proportion of deaths due to H1N1 among hospitalized patients compared to non-ethnic minorities. Favours non-ethnic minorities means that non-ethnic minorities experienced a lower proportion of deaths due to H1N1 among hospitalized patients compared to ethnic minorities.