Wednesday, September 23, 2009

Preliminary Results for Pandemic H1N1 Vaccine Trials in Children

Since mid-August, the National Institute of Allergy and Infectious Disease (NIAID), has sponsored a trial testing a 2009 H1N1 influenza vaccine in children provided by the drug manufacturer Sanofi Pasteur in Swiftwater, Pennsylvania.

Preliminary analysis of blood samples from a small group of trial participants shows that a single 15-microgram dose of a non-adjuvanted 2009 H1N1 influenza vaccine – the same dose that is in the seasonal flu vaccine – generates an immune response that is expected to be protective against 2009 H1N1 influenza virus in the majority of 10 to 17 year olds, eight to 10 days following vaccination. These results are similar to those recently reported in clinical trials of healthy adults. Younger children under the age of 10 however, generally had a less robust early response to the vaccine.

The trial is assessing the safety and immune responses to one and two doses of either 15 micrograms or 30 micrograms of vaccine. Data from the trial is being compared for three age groups: children 6 months to 35 months old; 3 to 9 years old; and 10 to 17 years old.

The preliminary results are based on blood samples taken 8 to 10 days after the first vaccination. Results were most impressive among children in the 10 to 17 age group; of 25 volunteers who received one 15-microgram dose of vaccine, 76% showed a high immune response. The immune responses in children nine years old 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 micrograms of vaccine, while in the youngest group of 20 children between 6 months to 35 months old, a single 15-microgram dose of vaccine produced a strong immune response in only 25% of recipients.

Study investigators are also collecting blood samples from the volunteers approximately three 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, says NIAID Director Dr. Anthony S. Fauci MD.

The news that a single-dose H1N1 vaccine may be extremely effective, as opposed to a two-dose regimen, could have significant implications for leaders in countries that will have surplus vaccines, and for low-income countries that may have difficulty meeting the demands for the vaccine. According to a Reuters report, some European states have begun exploring how they will divvy up excess stocks of the vaccine. "The European Union's executive arm said it would encourage 'a common approach to cross-border sharing and voluntary sale within the EU,'" the news service writes, adding, "Some countries have already included a provision in contracts with manufacturers stating that unused vaccines can be sold to other countries".

To view the NIAID press release in its entirety, please visit

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