Kiwako Yamamoto-Hanada et al.

Adjuvants used in inactivated vaccines often upregulate type 2 immunity, which is dominant in allergic diseases. We hypothesised that cumulative adjuvant exposure in infancy may influence the development of allergies later in life by changing the balance of type 1/type 2 immunity. We examined the relationship between immunisation with different vaccine types and later allergic disease development.

… The prevalence of wheeze, eczema and physician- diagnosed asthma at 1 year of age for the entire cohort of study participants was 19.9%, 18.4–18.7% and 2.5– 2.6%, respectively.

… Because inactivated vaccines generally contain adjuvants, our finding that initial immunisation with more types of inactivated vaccines is associated with the development of asthma or eczema at 12 months of age may implicate adjuvant exposure as a potential risk factor for the development of allergic diseases.

… Aluminium is the most commonly used adjuvant in human inactivated vaccines because this adjuvant stimulates type 2 immune responses … Although we were unable to identify the mechanism of how inactivated vaccines alter immunity because our study was epidemiological, we speculate that it involved the induction of type 2 responses.

… Although we recognise that immunisation is indispensable for the global elimination of various diseases, this large-scale birth cohort study demonstrated that the prevalence of asthma, wheeze and eczema in children at 12 months of age was associated with the administration of a larger number of types of inactivated vaccines at the initial immunisation before 6 months of age.