Children under age 10 would need two doses of the A/H1N1 vaccine while children ages 10 and older would need just one shot, a U.S. health official said Monday.

Early trials show that younger children are not having a robust immune reaction to the A/H1N1 flu vaccine, and that they would likely need to have their doses 21 days apart, Dr. Anthony Fauci, director of the National Institute of Allergy and Infectious Diseases, told reporters in a telephone briefing.

Protection kicks in for older children within eight to 10 days of the shot, just like it does for adults, Fauci said. These results were similar to those recently reported in the clinical trials of healthy adults.

"This is very encouraging news," Fauci announced. "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 A/H1N1 flu vaccine will require just one 15-microgram dose for children 10 to 17 years of age, he added.

Fauci said these were welcome results, as the A/H1N1 flu was causing widespread infections among children.

The vaccine being tested in this trial is manufactured by Sanofi Pasteur Inc. Like inactivated seasonal flu vaccines, the vaccine contains a purified part of a killed virus and cannot cause flu.

The U.S. Food and Drug Administration approved four vaccines against the A/H1N1 flu virus on Sept. 15. The vaccines are made by CSL Ltd., MedImmune LLC, Novartis Vaccines and Diagnostics Ltd., and Sanofi Pasteur Inc. All four firms produce the vaccines using the same process, and have a long record of producing safe seasonal influenza vaccines.

The U.S. government has ordered 195 million doses of A/H1N1 vaccine from the five drug makers.

Source: Xinhua