Observational
studies indicate that vitamin D deficiency is a predisposing
factor for infections and may contribute to increased
risk of LRTI and URTI [7, 9, 18, 20]. One study reported that
vitamin D status is associated with early childhood LRTI and
interventions to improve vitamin D status can reduce the burden
of LRTI in early childhood [18]. Similarly, the authors
found that serum vitamin D levels in patients with RRI were
lower than those in the control group. Magnus et al. showed
that higher maternal mid-pregnancy 25(OH)D level was associated
with a modestly reduced risk of recurrent LRTI by
36 mo, but was not associated with current asthma at 36 mo