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| |  Two Doses of H1N1 Vaccine May Be Required for Younger Children BETHESDA, Md -- September 21, 2009 -- Early results from a trial testing a 2009 influenza A(H1N1) vaccine in children looks promising, according to the National Institute of Allergy and Infectious Diseases (NIAID), part of the National Institutes of Health, Bethesda, Maryland. Preliminary analysis of blood samples from a small group of trial participants shows that a single 15-mcg dose of a non-adjuvanted 2009 H1N1 vaccine (the same dose that is in the seasonal flu vaccine) generates an immune response that is expected to be protective against the 2009 H1N1 influenza virus in the majority of children aged 10 to 17 years 8 to 10 days following vaccination. These results are similar to those recently reported in clinical trials of healthy adults. Younger children generally had a less robust early response to the vaccine. “This is very encouraging news,” said Anthony S. Fauci, MD, NIAID. “As we had hoped, responses to the 2009 H1N1 influenza vaccine are very similar to what we see with routinely used seasonal influenza vaccines made in the same way. It seems likely that the H1N1 flu vaccine will require just one 15-mcg dose for children 10 to 17 years of age. The 2009 H1N1 influenza virus is causing widespread infections among children, so these are welcome results.” The ongoing trial began in mid-August at 5 sites nationwide. The trial is assessing the safety and immune responses to 1 and 2 doses of either 15 mcg or 30 mcg of vaccine. Data from the trial is being compared for 3 age groups: children aged 6 to 35 months; children aged 3 to 9 years; and children aged 10 to 17 years. The preliminary results are based on blood samples taken 8 to 10 days after the first vaccination. Immune responses were strongest among the oldest children; those aged 10 to 17 years. In this group of 25 children, a strong immune response was seen in 76% who received one 15-mcg dose of vaccine. The immune responses in children aged 9 years and younger were not as strong. Among 25 volunteers aged 3 to 9 years old, a strong immune response was seen in 36% of those given 15 mcg of vaccine. In the youngest group, 20 children aged 6 to 35 months old, a single 15-mcg dose of vaccine produced a strong immune response in 25% of recipients. “These results are not unexpected and are both similar to what is seen with seasonal influenza vaccines and consistent with what we and our colleagues at the US Food and Drug Administration anticipated,” noted Dr. Fauci. Study investigators are also collecting blood samples from the volunteers approximately 3 weeks after both the first and second injections. It is anticipated that the immune response to the 2009 H1N1 influenza vaccine will be similar to that of seasonal influenza vaccination and will continue to rise for several weeks following vaccination, said Dr. Fauci. The study is being closely monitored by the trial physicians and staff as well as by an independent safety monitoring committee. SOURCE: National Institutes of Health
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