Abstract

Vitamin D deficiency has been implicated in risk of respiratory illness. We determined whether serum vitamin D levels are related to influenza vaccine response measured by hemagglutinin antibody inhibition (HAI) titer in adults aged ≥50 years old. The study was a prospective cohort study conducted over two influenza seasons (fall 2008–spring 2009 and fall 2009–spring 2010) in Marshfield, WI and Nashville, TN including 1103 community-dwelling adult volunteers ≥50 years of age. Pre-vaccination levels of serum vitamin D and HAI titer levels pre- and 21–28 days post-influenza vaccination were measured. Seroprotection was defined as HAI ≥40; seroconversion was defined as ≥4-fold rise in HAI titers from pre- to post-vaccination. More than 25% of participants were vitamin D deficient (<25 ng/mL). Vitamin D measured as a continuous variable was not related to pre- or post-vaccination seroprotection or seroconversion for any vaccine strain in any year. Vitamin D deficiency was associated with a greater frequency of post-vaccination seroprotection for seasonal H1N1 in the first year of the study, but was not related to seroprotection or seroconversion for any other strain in either year. No consistent association was found between vitamin D levels or vitamin D deficiency and serologic response to influenza vaccination in older adults. Cell-mediated immune parameters should also be explored in order to further investigate possible relationships between micronutrient status and influenza vaccine response.