ArticleInternational journal for equity in health2025
Independent and joint associations of sex and birth order with non‑national immunization program vaccine coverage among Chinese children: a cross-sectional analysis.
Article in International journal for equity in health, 2025. The graph could read no effect estimate from its abstract, so it casts no vote on the map. Cited by 1 paper.
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1 citing paper in PubMed.
- From midlife emergence to old-age divergence: an empirical study on structural gendered ageism in health service utilization in Tibet.International journal for equity in health · 2025Article
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Abstract
backgroundIn response to declining fertility rates, China implemented universal two- and three-child policies, leading to an increase of multi-child families. However, little is known whether and how these policy changes influenced the uptake of non-National Immunization Program (non-NIP) vaccines. We evaluated associations of sex and birth order with non-NIP vaccine coverage in 1-6-year-old children in China.
methodsOur study was a cross-sectional survey of caregivers of 1-6-year-old children in Zhejiang and Henan Provinces in 2022. We obtained information on sex, birth order, vaccination history, and family socio-demographics and determined uptake of five commonly-used non-NIP vaccines for infants [Haemophilus influenza b (Hib), varicella, rotavirus, enterovirus 71 (EV71), and 13-valent pneumococcal (PCV13) vaccines]. Children were considered vaccinated if they received the first dose of at least three of these vaccines. Log-binomial regression models were used to estimate prevalence ratios (PRs) and 95% confidence intervals (CIs) for independent and joint associations of sex and birth order with non-NIP vaccine coverage, and multiplicative and additive interactions of sex and birth order.
resultsA total of 1611 children with accompanying parents/guardians were included in the survey; 48.0% (n = 773) were girls; the median age was 3.3 years (interquartile range 2.0-4.8); and 824 (51.1%) were first-born children, 578 (35.9%) were second-born children, and 209 (13.0%) were third-or-later born children. Coverage of non-NIP vaccines varied by sex and birth order, ranging from 58.2% for first-born boys to 28.4% for third-or-later born girls. Coverage among girls was less than among boys (PR: 0.91, 95% CI: 0.82-1.00), but the sex differences were not significant after adjusting for sociodemographic factors (PR: 0.94, 95% CI: 0.86-1.03). Compared with first-born children, coverage PRs were 0.85 (0.76-0.93) for second-born children and 0.82 (0.65-1.00) for third-or-later born children (p for trend < 0.001). Sex and birth order had joint effects on coverage, with the lowest coverage PRs in the third-or-later born girls (0.71, 95% CI: 0.49-0.97), compared to first-born boys. Multiplicative interactions of sex and birth order were significant (PR: 0.86, 95% CI: 0.75-0.98 in second-born girls).
conclusionsBirth order of children was independently associated with non-NIP vaccines coverage, whereas sex showed no significant. However, sex and birth order were jointly associated with receipt of non-NIP vaccines, with later born children and girls having significantly lower coverage than first-born boys. In the context of the three-child policy in China, interventions to promote non-NIP vaccine equity should consider children's sex and birth order.
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