CSU 53/2009: LATE VACCINATION IN DEVELOPING COUNTRIES

Tuesday, 8th of September 2009

CHILD SURVIVAL UPDATE 53/2009: LATE VACCINATION IN DEVELOPING COUNTRIES

Writing in The Lancet, Clark and Sanderson review data from 45 Demographic
and Health Surveys to see whether, for example children get their third DPT
at 14 weeks, and measles vaccine at 9 months. Late vaccination is common.

This study simply analyzes the survey data. To gauge the epidemiological
importance of late vaccination, one would need to compare the survey data
to age-specific incidence and mortality data.

Good reading.

Bob Davis

|------|1: Lancet. 2009 May 2;373(9674):1543-9. Epub 2009 Mar 19.
Comment in:
Lancet. 2009 May 2;373(9674):1499-500.
Timing of children's vaccinations in 45 low-income and middle-income
countries: an analysis of survey data.
Clark A, Sanderson C.
Department of Public Health and Policy, London School of Hygiene
and Tropical Medicine, London, UK.

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.