Are Higher Vitamin D Levels Associated with Improved Influenza Vaccine Immunogenicity and Fewer Healthcare Encounters for Respiratory Infections among Young Adults?

BACKGROUND: Influenza continues to cause significant morbidity and mortality each year. Vaccination is the primary prevention; however, its effectiveness may be limited even among young, healthy adults. Vitamin D deficiency is highly prevalent and may be associated with poor vaccine immunogenicity and an increased risk for respiratory infections. METHODS: We conducted a retrospective cross-sectional study among young, healthy military personnel to evaluate the associations between 25(OH)D levels with post-influenza vaccination antibody titers (seroprotection defined as a titer of ≥1:40 post-vaccination) and healthcare encounters for respiratory infections during the 2009–2010 influenza season. 25(OH)D levels were analyzed as continuous and categorical [normal (>30 ng/mL), insufficient (20–30 ng/mL), and deficient (<20 ng/mL)] variables. Separate univariate and multivariable logistic regression models were utilized to determine the associations between 25(OH)D levels with antibody responses and respiratory conditions adjusting for possible confounders. RESULTS: A total of 437 subjects were evaluated. Most participants were young adults (91% were 18–39 years of age), 50% were male, and 56% resided in the southern U.S. Overall, 152 (35%) were vitamin D deficient, 167 (38%) insufficient, and 118 (27%) had normal 25(OH)D levels. There were no demographic differences by 25(OH)3 category. Only 224 (51%) demonstrated a seroprotective anti-influenza post-vaccination titer, which did not vary by categorical 25(OH)D levels [vitamin D deficient vs. normal: OR 1.10 (0.68–1.78) and insufficient vs. normal: OR 1.25 (0.78–2.01)] or continuous vitamin D levels [OR 0.98 (0.84–1.15)]. There were no associations with respiratory diagnoses between the vitamin D groups. CONCLUSION: Vitamin D insufficiency and deficiency were highly prevalent despite evaluating a young, healthy adult population. There were no significant associations between 25(OH)D levels and post-vaccination antibody titers or respiratory infections. Strategies for improving influenza vaccine responses are needed since only one-half of vaccinees demonstrated seroprotective anti-influenza titers. DISCLOSURES: All authors: No reported disclosures.