Swine flu milder than seasonal flu, vitamin D helps prevent both
A new study in the September 8 issue of Journal of American Medical Association suggests that the 2009 pandemic swine flu virus H1N1 had lower risk of most serious complications compared to recent seasonal flu strains. Another study suggests vitamin D can be better than influenza vaccine at preventing flu.
Edward A. Belongia, M.D., of the Marshfield Clinic Research Foundation, Marshfield, Wisc., and colleagues compared the characteristics of pandemic and seasonal flu A infections occurring in a defined population and found the 2009 pandemic H1N1 did not cause more hospitalizations and pneumonia, which are severe complications of influenza.
The analysis was based on data from 6,874 children and adults living in a 14-zip code area in Wisconsin, who had subjective fever, chills, or cough of fewer than eight days. These patients were interviewed and tested for influenza A during the 2007 - 2008 and 2008 - 2009 flu season and from May to Nov 2009.
Of the patients, 545 got infected with swine flu or 2009 pandemic H1N1 flu, 221 seasonal H1N1 and 632 patients with H3N2 virus.
Here is what the researchers found, according to a press release by the medical journal:
In children, 2009 H1N1 infection was not associated with either hospital admission or pneumonia compared with seasonal H1N1 or H3N2. Hospital admission occurred within 30 days for 6 of 395 children with 2009 H1N1 (1.5 percent), 5 of 135 with seasonal H1N1 (3.7 percent), and 8 of 255 with H3N2 (3.1 percent). Among adults, hospital admission occurred in 6 of 150 with 2009 H1N1 (4.0 percent), 2 of 86 with seasonal H1N1 (2.3 percent), and 17 of 377 with H3N2 (4.5 percent).
Among adults, pneumonia occurred in 4.0 percent of those with 2009 H1N1 infection; 2.3 percent of patients with seasonal H1N1; and 1.1 percent of those with H3N2 infection. Pneumonia occurred in 2.5 percent of children with 2009 H1N1; 1.5 percent of children with seasonal H1N1; and 2.0 percent with H3N2. There were no significant differences by strain in the proportion of children or adults with any serious outcome (pneumonia or hospital admission) during the 30 days after onset.
The researchers concluded that "the clinical manifestations and risk of hospital admission are similar for 2009 H1N1 and other seasonal influenza A strains among those presenting for medical care and documented to have influenza infection."
They also say in their report "children were disproportionately affected by 2009 H1N1 infection, but the perceived severity of symptoms and risk of serious outcomes (pneumonia or hospital admission) were not increased in children with 2009 H1N1 infection relative to seasonal influenza A viruses."
The Centers for Disease Control and Prevention (CDC) estimated that 43 million to 89 million pandemic 2009 influenza A(H1N1) infections occurred in the United States from April 2009 through April 10,2010 resulting in 274,000 H1N1 related hospitalizations and 12,470 deaths in the U.S., according to the background information in the study report.
Early media reports suggest that children with vitamin D deficiency or certain health conditions related to Vitamin D deficiency are at higher risk for severe complications induced by the 2009 pandemic flu virus H1N1 or swine flu.
Observations by two physicians, one in Wisconsin and another in Georgia suggest that taking high doses of vitamin D can highly effective in preventing swine flu and seasonal flu. Dr. John Cannell has reported what the physicians observed in his newsletter released earlier.
The CDC says that swine flu vaccine will be combined this year with the seasonal flu vaccine for the coming flu season. That means that one flu shot will be used to prevent both swine flu and seasonal flu. Unfortunately, the efficacy of influenza vaccine is often notoriously low because the virus used to construct the vaccine often does not match the circulating strains well.
Urashima M. and colleagues from Jikei University School of Medicine in Tokyo Japan conducted a clinical trial and found that vitamin D supplementation almost halved incidence of seasonal flu or influenza A among school children.
The randomized, double-blind, placebo-controlled trial was conducted between Dec 2008 and March 2009, during which school children were given 1200 International Units per day and cases of influenza A were counted.
During the trial, 10.8 percent of children who took vitamin d supplements got infected with influenza A compared to 18.6 percent among the children who did not get vitamin D. The risk of influenza A was reduced by 42 percent.
Among those who had not been taking other vitamin D supplements and those who started nursery school after three years, the risk was reduced by 67 percent.
Among children who were previously diagnosed with asthma, asthma attacks occurred to 2 children who took vitamin D supplements compared to 12 who did not get vitamin D.
They reported their findings in the May 2010 issue of American Journal of Clinical Nutrition.
This study along with the observations reported by physicians suggests that it is important for children and adults regardless of their vaccination status to get sufficient vitamin D either through exposure to sunshine or taking vitamin D supplements.
One study published early in Nature proved that vitamin D is protective against flu infection invlufing swine flu by boosting human innate immunity.
By David Liu
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