Infants’ immunisations, their timing and the risk of allergic diseases (INITIAL): an observational prospective cohort study protocol

This paper presents the protocol for the INITIAL study, a prospective observational cohort designed to investigate whether the timing, type, or number of vaccines administered in the first year of life is associated with subsequent allergic disease incidence. Allergic outcomes (asthma, atopic dermatitis, rhinoconjunctivitis, food allergy) will be assessed using the ISAAC questionnaire with mandatory physician confirmation. The authors acknowledge that a randomised controlled trial was deemed ethically unfeasible due to high vaccine recommendation rates. The study aims to adjust for multiple confounders identified from prior literature and to record parental vaccination attitudes. Limitations acknowledged by the authors include potential selection bias, performance bias from varied recruitment sources, participant dropout over the long follow-up period, possible need to redefine comparison groups if the unvaccinated group proves too small, and that the 5-year observation window may be insufficient to detect relevant allergy differences.