Using the Immunization Information System to determine vaccination coverage rates among children aged 1-7 years: a report from Zhejiang Province, China

Abstract

Background: The Zhejiang Immunization Information System (ZJIIS) was established in 2004. This study described the coverage rates of NIP vaccines in Zhejiang Province using the ZJIIS.

Methods: Children aged 1-7 years (born from 1 January 2005 to 31 December 2011) registered in ZJIIS were enrolled in this study. All immunization records were obtained from the ZJIIS on 31 December 2012. The cohort method had been used for identifying trends and patterns in vaccine administration. Immunization coverage estimates were analyzed for both individual NIP vaccines and "Fully immunized" by age group, birth cohort, immigration status, and geography area. We also examined the timeliness vaccination for the 2010 birth cohort.

Results: A total of 3,579,896 children were registered in ZJIIS. All the vaccines and doses which scheduled to be given at ≤ 12 months of age exceeded 90%. There was substantial decrease trend in the vaccines scheduled at >12 months of age and most of these vaccines were below 90%. The coverage of migrant children was lower than for resident children and the coverage of WenZhou (WZ), Zhoushan (ZS) and TaiZhou (TZ) was lower than other municipalities for most of vaccines across all the birth cohorts. Nearly 20%-30% of children of 2010 birth cohort delayed for the primary series vaccination scheduled at ≤ 12 months of age, especially among migrant children.

Conclusions: The ZJIIS is useful in tracking vaccine coverage of children aged 1-7 years and the data provided by ZJIIS reflected the fact that NIP delivery was improving in Zhejiang Province, while identifying some areas for improvement. We recommend continuing surveillance to estimate of vaccine coverage through ZJIIS. Immunization strategies such as Assessment, Feedback, Incentives, and Exchange program, reminder/recall activity, home visits, school entry requirements and school-based clinics could be used to reach a higher coverage of the population.

Figure 1

Trends in vaccination coverage estimates for individual vaccines at 12 months of age (≥3 dose of Hep B, PV and DPT, ≥1 dose of BCG, MCV, JEV, “Fully immunized”), by 3-month birth cohorts born between 1 January 2005 to 31 December 2011. Coverage assessment date was 12 months after the last birth date of each cohort.

Figure 2

Trends in vaccination coverage estimates for individual vaccines at 24 months of age (≥4 doses of DPT, ≥3 dose of Hep B and PV, ≥2 dose of MCV and MPV-A, ≥1 dose of BCG, JEV, Hep A, “Fully immunized”), by 3-month birth cohorts born between 1 January 2005 to 31 December 2010. Coverage assessment date was 12 months after the last birth date of each cohort.

Figure 3

Timeliness of Hep B₃, PV₃, DPT₃ and MCV₁ by immigration status- cohort born in 2010. Percentage coverage = number of children who received vaccine dose at particular ages/the total number of children who received the vaccine dose (doses never administered or recorded were excluded.