Health officals announced this week that an H5N1 vaccine had been developed at St. Jude Children's Research Hospital. Researchers have been working on a vaccine since 2000, using a technique called reverse genetics, and the current clinical trials started last spring. The New York Times Sunday edition featured an article on the vaccine with graphics. The gist of the study is that an increasing dose of the vaccine produced a commensurate antibody response in data from about a quarter of the clinical trials 452 subjects.
Although the study provides some proof of concept, researchers who were told about the results caution about being overly optimistic for a couple of reasons. The first is that like other viruses (flu and HIV), H5N1 mutates rapidly, so that the strain that the vaccine is derived from may not match an epidemic strain, meaning the vaccine wouldn't protect against all strains necessarily. In fact the strain used to make this vaccine is significantly less virulent then the strain that is currently active in Asia.
The second reason, according to the article, is that the dose needed for a vaccination in these trials is many times what is usually needed for a flu vaccine - two doses of approximately 90 micrograms given 4 weeks apart. Typical flu vaccines use two doses of 15 micrograms, which means that stockpiles would have to be significantly larger then they are now.
An interesting feature of these reports was that they were announced by Anthony Fauci, director of the National Institute of Allergy and Infectious Diseases in newspaper interviews ahead of the full study results- perhaps because of the mounting fears about the spread of the disease in Asia. Usually research results are peer reviewed ahead of general news publication.
