Delay in diphtheria, pertussis, tetanus vaccination is associated with a reduced risk of childhood asthma.
Level 3 - non-randomized controlled study
Retrospective longitudinal cohort study
PubMed 18207561 · doi:10.1016/j.jaci.2007.11.034
What was done
This was a retrospective longitudinal cohort study of children born in Manitoba in 1995 with complete immunization and healthcare records from birth to age 7 years. Researchers analyzed the association between the timing of whole-cell diphtheria, pertussis, tetanus (DPT) immunization and asthma diagnosis at age 7 years using multivariable logistic regression among children receiving at least 4 doses.
What was found
Among 11,531 children who received at least 4 DPT doses, delaying the first dose by more than 2 months was associated with a reduction of asthma risk to 1/2 (exact adjusted OR and CI for this specific metric were not stated in the abstract). Delays across all of the first 3 doses resulted in an adjusted odds ratio for asthma of 0.39 (95% CI, 0.18-0.86).
Why it matters
This study suggests that variation in the timing of early childhood immunizations may explain conflicting findings across prior observational studies regarding vaccine exposure and asthma risk.
Limits
The retrospective administrative database design cannot exclude residual confounding regarding why vaccines were delayed (such as early childhood illnesses or health-seeking behaviors). The study evaluated whole-cell DPT in a 1995 birth cohort, which may not generalize to modern acellular pertussis formulations.
Cited by
- supports Published scientific studies indicate that delaying certain childhood vaccines decreases the risk of asthma and eczema.