Peer-reviewed article
Zero-dose children and the immunisation cascade: Understanding immunisation pathways in low and middle-income countries
Bianca O. Cata-Preta, Thiago Melo Santos, Tewodaj Mengistu, Daniel R. Hogan, Aluísio J. D. Barros et al. ·
Summary
Written by AI, not yet AICS's view · claude-haiku-4-5-20251001This study examined immunisation coverage patterns in 92 low- and middle-income countries, tracking how children progress from receiving no vaccines (zero-dose) to full immunisation. About 8% of children aged 12 to 23 months received no vaccines, while 71% received all four basic infant vaccines (BCG, polio, DPT, MCV). Children who received their first vaccine were highly likely to complete the full schedule. Significant inequalities were found by household wealth, with the poorest families having nearly four times higher zero-dose rates than the wealthiest.
Key points
- 7.7% of children in 92 LMICs were zero-dose (received no routine vaccinations)
- 70.9% of children aged 12-23 months received all four basic vaccine types
- 76.8% of children who received the first vaccine subsequently received all four vaccine types
- Zero-dose prevalence ranged from 12.5% in the poorest wealth quintile to 3.4% in the wealthiest, showing sharp inequalities
- Dropout rates between vaccines were relatively low: 4% after BCG, 14% between DPT1 and DPT3, and 9% between DPT3 and MCV
Limitations
The study uses survey data from different countries and time periods (since 2010), so methodological consistency and temporal comparability may vary. The analysis does not examine reasons for zero-dose status or identify specific barriers to immunisation access beyond wealth-related factors.
Abstract
INTRODUCTION: Zero-dose prevalence refers to children who failed to receive any routine vaccination. Little is known about the "immunisation cascade" in low- and middle-income countries (LMICs), defined as how children move from zero dose to full immunisation. METHODS: Using data from national surveys carried out in 92 LMICs since 2010 and focusing on the four basic vaccines delivered in infancy (BCG, polio, DPT and MCV), we describe zero-dose prevalence and the immunisation cascade in children aged 12 to 23 months. We also describe the most frequent combinations of vaccines (or co-coverage) among children who are partially immunized. Analyses are stratified by country income groups, household wealth quintiles derived from asset indices, sex of the child and area of residence. Results were pooled across countries using child populations as weights. RESULTS: In the 92 countries, 7.7% were in the zero-dose group, and 3.3%, 3.4% and 14.6% received one, two or three vaccines, respectively; 70.9% received the four types and 59.9% of the total were fully immunised with all doses of the four vaccines. Three quarters (76.8%) of children who received the first vaccine received all four types. Among children with a single vaccine, polio was the most common in low- and lower-middle income countries, and BCG in upper-middle income countries. There were sharp inequalities according to household wealth, with zero-dose prevalence ranging from 12.5% in the poorest to 3.4% in the wealthiest quintile across all countries. The cascades were similar for boys and girls. In terms of dropout, 4% of children receiving BCG did not receive DPT1, 14% receiving DPT1 did not receive DPT3, and 9% receiving DPT3 did not progress to receive MCV. INTERPRETATION: Focusing on zero-dose children is particularly important because those who are reached with the first vaccine are highly likely to also receive remaining vaccines.