To the Editors:
The recent paper on association of 2009 pandemic influenza A (H1N1) infection with parapneumonic empyema in children in Utah1 is further evidence that pneumonia often follows influenza infection. The United States Public Health Service conducted rather thorough surveys of case-fatality rates from the 1918 influenza pandemic A (H1N1) in 12 communities.2 Case-fatality rates varied from 0.78 per 100 in San Antonio, TX, to 3.14 per 100 in New London, CT. Most of the deaths were attributed to pneumonia, and deaths generally occurred about 10 days after influenza infection. The cytokine storm that often accompanies influenza infection leads to disruption of the epithelial lining of the lung, permitting the often present Streptococcus pneumoniae and Streptococcus pyogenes bacteria to invade, leading to pneumonia. In an ecologic study using indices for solar ultraviolet B (UVB) in summer and winter, it was found that summertime UVB explained 46% of the variance.3 Two explanations were provided for this finding: reduced proinflammatory cytokine production and the antibacterial actions of cathelicidin, induced by 1,25-dihydroxyvitamin D. A paper published subsequently provided more support for the role of solar UVB and vitamin D in reducing the risk of invasive pneumococcal disease risk in Philadelphia, Pennsylvania.4
Vitamin D can also reduce the risk of influenza A infection. A recent randomized controlled trial of school children in Japan taking 1200 IU/d or 200 IU/d of vitamin D3 reported a relative risk of developing influenza A infection of 0.36 (95% confidence interval, 0.17–0.79) for those not taking additional vitamin D.5 Although outside the scope of this letter, it is noted that the groups of people who had the most serious complications from the recent A (H1N1) influenza tended to have low serum 25-hydroxyvitamin D [25(OH)D] levels: pregnant women, Australia Aborigines, Canadian First Nation people, patients with diabetes, obese, and children with neurologic diseases.
Thus, during the influenza season, people would be well advised to take steps to increase their serum 25(OH)D concentrations to above 40 ng/mL. In winter, serum 25(OH)D values are generally near 20 ng/mL. Each 1000 IU/d of vitamin D3 raises serum 25(OH)D values by about 10 ng/mL for the average sized person. People of all ages can safely take 5000 to 10,000 IU/d of vitamin D3 for an extended time unless they have granulomatous diseases, in which case smaller doses are advised. Those diagnosed with either seasonal or pandemic influenza should be advised to take higher doses for the duration of the infection.
William B. Grant, PhD
Sunlight, Nutrition, and Health Research
San Francisco, CA
1. Ampofo K, Herbener A, Blaschke AJ, et al. Association of 2009 pandemic influenza A (H1N1) infection and increased hospitalization with parapneumonic empyema in children in Utah. Pediatr Infect Dis J.
2. Britten RH. The incidence of epidemic influenza, 1918–19. Public Health Rep
3. Grant WB, Giovannucci D. The possible roles of solar ultraviolet-B radiation and vitamin D in reducing case-fatality rates from the 1918–1919 influenza pandemic in the United States. Dermatoendocrinol
4. White AN, Ng V, Spain CV, et al. Let the sun shine in: effects of ultraviolet radiation on invasive pneumococcal disease risk in Philadelphia, Pennsylvania. BMC Infect Dis
5. Urashima M, Segawa T, Okazaki M, et al. Randomized trial of vitamin D supplementation to prevent seasonal influenza A in schoolchildren. Am J Clin Nutr