Unintended adverse consequences of the introduction of new vaccines in Guinea-Bissau

Fisker AB, Hornshøj L, Rodrigues A, Balde I, Fernandes M, Benn CS, Aaby P. Effects of the introduction of new vaccines in Guinea-Bissau on vaccine coverage, vaccine timeliness, and child survival: an observational study (Lancet Global Health, In press) 

In 2008, the Guinean immunisation programme was modified. Diphtheria-Tetanus-Pertussis (DTP) was replaced by pentavalent vaccine (DTP-HiB-HepB), and yellow fever vaccine was added to be given together with measles vaccine at 9 months. In evaluating vaccination programmes, donors focus on vaccination coverage by 12 months of age and on vaccine wastage. Live vaccines which have to be dissolved prior to use and discarded 6 hours after dissolving, are typically produced in multi-dose vials. To reduce wastage, 10-dose measles and yellow fever vaccines are only be opened if at least 6 children have come for vaccination at the same time. Furthermore, children over 12 months of age do not count in the statistics, and hence they are no longer vaccinated.

The introduction of the new vaccines was associated with increased coverage and timeliness of DTP, but the median age of MV increased and coverage dropped. Lowering the coverage for MV is likely to have negative effects for overall child health.

A declining coverage for MV may have severe implication for child health. When vaccinations were still given to children aged >12 months in 1999-2004, 84% of children who were measles-unvaccinated by 12 months had received MV by 3 years of age. After 12 months of age, the mortality rate was 29% (10-44%) lower for measles-vaccinated than measles-unvaccinated children, the reduction being 41% (20-57%) for girls.

Read the article in Lancet Global Health