Statistical analysis plan for the OPTIMUM study: optimising immunisation using mixed schedules, an adaptive randomised controlled trial of a mixed whole-cell/acellular pertussis vaccine schedule

Infant Whole-Cell Versus Acellular Pertussis Vaccination in 1997 to 1999 and Risk of Childhood Hospitalization for Food-Induced Anaphylaxis: Linked Administrative Databases Cohort Study

BACKGROUND

Evidence suggests that children who had received an initial priming dose of whole-cell pertussis (wP) vaccine, rather than acellular pertussis (aP) vaccine, had a lower risk of developing IgE-mediated food allergy, the most common cause of anaphylaxis-related hospital presentations of childhood.

OBJECTIVE

To assess the association between wP versus aP vaccination in infancy and subsequent hospital presentations for anaphylaxis.

METHODS

This study was preregistered under PMID 34874968. Perinatal records for a cohort of New South Wales-born children (1997-1999) receiving their first dose of pertussis-containing vaccine before age 4 months were probabilistically linked to hospital and immunization records. We used adjusted Cox models to estimate hazard ratios (aHRs) and 95% CIs for anaphylaxis-coded hospitalizations.

RESULTS

There were 218,093 New South Wales-born children who received a first dose of wP or aP before age 4 months. Among these children, 86 experienced at least one hospitalization for food-induced anaphylaxis at age 5-15 years (range of events per patient, one to three). The person-time of follow-up was 1,476,969 years, and 665,519 years for children vaccinated with wP as a first dose (wP-1 children) and aP as a first dose (aP-1 children), respectively. The incidence rates for first hospitalization for food anaphylaxis were 3.5 (95% CI, 2.6-4.6) and 5.1 (95% CI, 3.5-7.1) per 100,000 child-years among wP-1 children and aP-1 children, respectively (aHR for wP vs aP = 0.47; 95% CI, 0.26-0.83). For first admission for venom anaphylaxis, the incidence rate was 4.9 (95% CI, 3.9-6.2) per 100,000 child-years among wP-1 children and 5.1 (95% CI, 3.5-7.1) per 100,000 child-years among aP-1 children (aHR for wP vs aP = 0.92; 95% CI, 0.53-1.60), and for all-cause anaphylaxis, the incidence rate was 10.6 (95% CI, 9.0-12.4) per 100,000 child-years among wP-1 children and 12.8 (95% CI, 10.2-15.8) per 100,000 child-years among aP-1 children (aHR for wP vs aP = 0.92; 95% CI, 0.53-1.60).

CONCLUSION

Vaccination with wP in infancy was associated with a lower risk of hospitalizations for food-induced anaphylaxis (and therefore severe IgE-mediated food allergy) occurring in childhood.