Background: Vaccinations are often delayed until well after the recommended ages, leaving many children exposed for longer than they should be. We estimated vaccination coverage at different ages, and delays in administration, in 45 low-income and middle-income countries.
Methods: We used data for 217 706 children from Demographic and Health Surveys between 1996 and 2005 (median 2002), which provided data for vaccination of children on the basis of events recorded on vaccination cards and interviews with mothers, with imputation of missing values and survival analysis. We devised an index combining coverage and delay.
Findings: For vaccinated children, the median of the median delays in the 45 countries was 2.3 weeks (IQR 1.4-4.6) for bacille Calmette-Guérin (BCG); 2.4 weeks (1.2-3.3) for diphtheria, tetanus, and pertussis (DTP1); 2.7 weeks (1.7-3.1) for measles-containing vaccine (MCV1); and 6.2 weeks (3.5-8.5) for DTP3. However, in the 12 countries with the longest delays for each vaccination, at least 25% of the children vaccinated were more than 10 weeks late for BCG, 8 weeks for DTP1, 11 weeks for MCV1, and 19 weeks for DTP3. Variation within countries was substantial: the median of the IQRs in the 45 countries for delay in DTP3 was 10.9 weeks, 7.9 weeks for MCV1, 5.4 weeks for BCG, and 5.3 weeks for DTP1. The median of the national coverage rates for DTP1 increased from 57% in children aged 12 weeks to 88% at 12 months, and for DTP3 from 65% at 12 months to 76% at 3 years.
Interpretation: The timeliness of children's vaccination varies widely between and particularly within countries, and published yearly estimates of national coverage do not capture these variations. Delayed vaccination could have important implications for the effect of new and established vaccines on the burden of disease.
Funding: WHO's Initiative for Vaccine Research.