Complete and on-time routine childhood immunisation: determinants and association with severe morbidity in urban informal settlements, Nairobi, Kenya

Abstract

Background: Completion of the full series of childhood vaccines on-time is crucial to ensuring greater protection against vaccine-preventable diseases.

Aim: To examine determinants of complete and on-time vaccination and evaluate the relationship between vaccination patterns and severe morbidity outcomes.

Subjects and methods: Vaccination information from infants in Nairobi Urban Health and Demographic Surveillance System was used to evaluate full and on-time vaccination coverage of routine immunisation. Logistic regression was used to identify determinants of full and on-time vaccination coverage. Cox regression model was used to evaluate the relationship between vaccination status and subsequent severe morbidity. A shared frailty cox model was fitted to account for the heterogeneity in hospitalisation episodes.

Results: Maternal age, post-natal care, parity, ethnicity, and residence place were identified as determinants of vaccination completion. Institutional deliveries and residence place were identified as the determinants of on-time vaccination. A significant 58% (confidence interval [CI]: 15–79%) (p = .017) lower mortality was observed among fully immunised children compared with not fully immunised. Lower mortality was observed among on-time immunised children, 64% (CI: 20–84%) compared to those with delays.

Conclusions: Improving vaccination timeliness and completion schedule is critical for protection against vaccine preventable diseases and may potentially provide protection beyond these targets.

Keywords:

• Health and Demographic Surveillance System
• fully immunised child
• vaccination delays
• childhood mortality
• longitudinal study
• non-specific effects of vaccines
• urban slums Kenya

Acknowledgements

The authors are highly indebted to the data collection team and the study participants.

Author contributions

MK: Participated in the overall conceptualization and inception of the idea of this manuscript, with lead roles in conducting literature review, data analysis, writing the results and discussion sections. SFM: assisted in conceptualization and writing the background and discussion section. EK-M: assisted in the conceptualization and writing the discussion section. HR: assisted in conceptualization and writing the methods section. PA: assisted in conceptualization and reviewing the discussion. ABF: assisted in conceptualization and reviewing the paper. EE: assisted in conceptualization and reviewing all sections of the paper. CBJ: provided stylistic and technical review of all sections of the paper. LK: reviewed the introduction and discussion sections of the paper. All the authors read and approved the final manuscript.

Disclosure statement

The authors declare that they have no competing interests.

Additional information

Funding

Projects which contributed data; Urbanisation, Poverty, and Health Dynamics (UPHD) research project funded by the Wellcome Trust [Grant Number GR 07830 M] and Monitoring and assessing the impact of vaccinations and other childhood interventions for both boys and girls, an INDEPTH Network collaboration project funded by the Danish Development Agency (DANIDA) [DFC Project no 09–09-105SSI]. GAVI, the Vaccine Alliance also funded several INDEPTH demographic surveillance system sites to analyse the determinants of children being fully immunised and the association with child survival. This research was also made possible through the generous core funding for the NUHDSS by the Bill and Melinda Gates Foundation [Grant# OPP1021893] and core funding for APHRC by The William and Flora Hewlett Foundation [Grant# 2009–40510], and the Swedish International Cooperation Agency (SIDA) [Grant# 2011–001578]. This study was supported by a grant from Danida Fellowship Centre and Styrelsen för Internationellt Utvecklingssamarbete.