Timeliness of Childhood Primary Immunization and Risk Factors Related with Delays: Evidence from the 2014 Zhejiang Provincial Vaccination Coverage Survey.

Yu Hu,Qian Li,Yaping Chen

doi:10.3390/ijerph14091086

Abstract

Background: this study aimed to assess both immunization coverage and timeliness, as well as reasons for non-vaccination, and identity the risk factors of delayed immunization, for the vaccines scheduled during the first year of life, in Zhejiang province, east China. Methods: A cluster survey among children aged 24–35 months was conducted. Demographic information and socio-economic characteristics of the selected child, the mother, and the household were collected. Immunization data were transcribed from immunization cards. Timeliness was assessed with Kaplan–Meier analysis for each vaccine given before 12 months of age, based on the time frame stipulated by the expanded program on immunization of China. Cox proportional hazard regression was applied to identify risk factors of delayed immunization. Results: A total of 2772 eligible children were surveyed. The age-appropriate coverage ranged from 25.4% (95% CI: 23.7–27.0%) for Bacillus Calmette–Guerin (BCG) to 91.3% (95% CI: 90.2–92.3%) for the first dose of oral poliomyelitis vaccine (OPV1). The most frequent reason for non-vaccination was parent’s fear of adverse events of immunization. Delayed immunizations were associated with mother having a lower education level, mother having a job, delivery at home, increasing number of children per household, and having a lower household income. Conclusions: Although the timeliness of immunization has improved since 2011, necessary steps are still needed to achieve further improvement. Timeliness of immunization should be considered as another important indicator of expanded program on immunization (EPI) performance. Future interventions on vaccination coverage should take into consideration demographic and socio-economic risk factors identified in this study. The importance of adhering to the recommended schedule should be explained to parents.

Highlights

To achieve effective control of vaccine preventable diseases (VPDs), a high coverage with efficacious vaccines is required
Over 95% of the surveyed children received all primary immunizations before 12 months of age, but few were immunized with these vaccines at the recommended age
A coverage rate of 90% at a later age may not be sufficient to assure the adequate protection of children, especially for the VPDs with high basic reproduction numbers, it has been indicated that rising immunization coverage would increase the timeliness of vaccination simultaneously [17]

Summary

Introduction

To achieve effective control of vaccine preventable diseases (VPDs), a high coverage with efficacious vaccines is required. The goal of the World Health Organization (WHO) for childhood immunization coverage is 90% [1,2]. In addition to high coverage, timeliness of vaccination is important for the success of the expanded program on immunization (EPI), especially a timely start of immunization for the first year of life, as the maternal antibody declines rapidly [3]. Delayed vaccination increased the risk time between the loss of maternal antibodies and the protection from vaccine-induced immunity, which negatively affects the herd immunity and contributes to the outbreaks of VPDs [6]. Public Health 2017, 14, 1086; doi:10.3390/ijerph14091086 www.mdpi.com/journal/ijerph

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