(Sep. 6, 2006) A vaccine being developed in China to protect humans against the H5N1 bird flu virus is safe and effective at low doses, researchers there report. However, pain, swelling, and fever were the most common side effects reported by study participants who received the vaccine.
A previous study found that 30 micrograms of the vaccine (which contains part of the H5N1 virus) given in two doses with an "adjuvant" (an additive that can increase effectiveness) produced a good immune response in humans.
However, this 30-microgram dose -- that has to be given in two doses -- means manufacturers would only be able to provide enough vaccine for 225 million people. A lower-dose vaccine may make it possible to vaccinate more people, the researchers reported Wednesday in the online edition of the journal The Lancet.
The vaccine tested in this new study contains a modified form of the whole H5N1 virus plus the adjuvant aluminum hydroxide. Vaccines created with whole viruses trigger a stronger immune response than vaccines made out of a part of the virus. However, whole-virus vaccines can cause more side effects.
This latest study included 120 people, ages 18 to 60, who received either two doses of a placebo or of the whole-virus vaccine at either 1.25, 2.5, 5, or 10 micrograms. After 56 days, all the different doses prompted the production of antibodies against the H5N1 virus. However, the best response was seen in people who received the 10-microgram dose of vaccine. (from forbes.com)