The Introduction of Diphtheria-Tetanus-Pertussis and Oral Polio Vaccine Among Young Infants in an Urban African Community: A Natural ExperimentOpen Access
Publication HistoryPublished online:January 31, 2017
Accepted:January 29, 2017
Received in revised form:January 21, 2017
Received:June 4, 2016
•When DTP and OPV were introduced in Guinea-Bissau in 1981, allocation by birthday resulted in a natural experiment of being vaccinated early or late.
•Between 3 and 5 months of age, children who received DTP and OPV early had 5-fold higher mortality than still unvaccinated children.
•In the only two studies of the introduction of DTP and OPV, co-administration of OPV with DTP may have reduced the negative effects of DTP.
Few studies have examined what happened to child survival when DTP and OPV were introduced in low-income countries. These vaccines were introduced in 1981 in an urban community in Guinea-Bissau from 3 months of age in connection with 3-monthly weighing sessions. Children were therefore allocated by birthday to receive vaccines early or late between 3 and 5 months of age. In this natural experiment vaccinated children had 5-fold higher mortality than not-yet-DTP-vaccinated children. DTP-only vaccinations were associated with higher mortality than DTP + OPV vaccinations. Hence, DTP may be associated with a negative effect on child survival.
We examined the introduction of diphtheria-tetanus-pertussis (DTP) and oral polio vaccine (OPV) in an urban community in Guinea-Bissau in the early 1980s.
The child population had been followed with 3-monthly nutritional weighing sessions since 1978. From June 1981 DTP and OPV were offered from 3 months of age at these sessions. Due to the 3-monthly intervals between sessions, the children were allocated by birthday in a ‘natural experiment’ to receive vaccinations early or late between 3 and 5 months of age. We included children who were
Among 3–5-month-old children, having received DTP (±OPV) was associated with a mortality hazard ratio (HR) of 5.00 (95% CI 1.53–16.3) compared with not-yet-DTP-vaccinated children. Differences in background factors did not explain the effect. The negative effect was particularly strong for children who had received DTP-only and no OPV (HR = 10.0 (2.61–38.6)). All-cause infant mortality after 3 months of age increased after the introduction of these vaccines (HR = 2.12 (1.07–4.19)).
DTP was associated with increased mortality; OPV may modify the effect of DTP.