Prevalence, geographical distribution and factors associated with pentavalent vaccine zero dose status among children in Sindh, Pakistan: analysis of data from the 2017 and 2018 birth cohorts enrolled in the provincial electronic immunisation registry

Abstract

Objectives: To estimate the prevalence of zero dose children (who have not received any dose of pentavalent (diphtheria, tetanus, pertussis, Haemophilus influenzae type B and hepatitis B) vaccine by their first birthday) among those who interacted with the immunisation system in Sindh, Pakistan along with their sociodemographic characteristics and risk factors.

Design and participants: We conducted a descriptive analysis of child-level longitudinal immunisation records of 1 467 975 0-23 months children from the Sindh's Zindagi Mehfooz (Safe Life) Electronic Immunisation Registry (ZM-EIR), for the birth cohorts of 2017 and 2018.

Setting: Sindh province, Pakistan which has a population of 47.9 million people and an annual birth cohort of 1.7 million.

Primary and secondary outcome measures: The primary outcome measure was zero dose status among enrolled children. Logistic regression was performed to identify the risk factors associated with the zero dose status.

Results: Out of 1 467 975 children enrolled in the ZM-EIR in Sindh, 10.6% (154 881/1 467 975) were zero dose. There were sharp inequities across the 27 districts. Zero dose children had a lower proportion of hospital births (28.5% vs 34.0%; difference 5.5 percentage points (pp) (95% CI 5.26 to 5.74); p<0.001) and higher prevalence from slums (49.5% vs 42.3%; difference 7.2 pp (95% CI 6.93 to 7.46); p<0.001), compared with non-zero dose children. Children residing in urban compared with rural areas were at a higher risk (relative risk (RR): 1.20; p<0.001; 95% CI 1.18 to 1.22), while children with educated compared with uneducated mothers were at a lower risk of being zero dose (RR: 0.47-0.96; p<0.001; 95% CI 0.45 to 0.98).

Conclusions: Despite interacting with the immunisation system, 1 out of 10 children enrolled in the ZM-EIR in Sindh were zero dose. It is crucial to monitor the prevalence of zero dose children and investigate their characteristics and risk factors to effectively reach and follow-up with them.

Keywords: community child health; paediatric infectious disease & immunisation; public health.

Figure 1

Crude male-to-female (M:F) ratio among zero dose, non-zero dose, covered zero dose and not covered zero dose children from 2017 and 2018 birth cohorts enrolled in Zindagi Mehfooz (Safe Life) Electronic Immunisation Registry in Sindh province, by district (n=1 467 975).

Figure 2

Up-to-date vaccination coverage at 24 months among zero dose and non-zero dose children from 2017 and 2018 birth cohorts enrolled in Zindagi Mehfooz (Safe Life) Electronic Immunisation Registry in Sindh province (n=1 467 975). IPV, inactivated polio vaccine; OPV, oral polio vaccine; PCV, pneumococcal conjugate vaccine; Penta, pentavalent.

Figure 3

Enrolment locations of zero dose and non-zero dose children from 2017 and 2018 birth cohorts enrolled in Zindagi Mehfooz (Safe Life) Electronic Immunisation Registry through routine and enhanced outreach and their displacement distance to the nearest Expanded Programme on Immunisation fixed sites (in km) in Karachi and Union Council Gujjro, Karachi.