Early life exposure to a specific, live bacterial strain can reduce susceptibility to asthma. We confirmed this protective efficacy here, using the gold standard of in vivo airway hyper-reactivity. We also determined that a therapeutic Lm-vaccine based approach might provide benefit, but likely only after repeat immunization. While our findings suggested that Lm decreased a Th2 response, we here discovered that neonatal prophylactic Lm vaccination did not exacerbate the development of the Th-1/17 driven disease, HP. Together this argues that Lm immunization balances rather than biases immune ontogeny. This sets the framework to test multiple hypotheses on the mechanism of immune skewing towards or away from the development of asthma and other atopic diseases.