To produce the new vaccine, the scientists used a mutated common cold virus, known as an adenovirus, as a delivery system for important genes from two types of the H5N1 avian influenza. The adenovirus is incapable of multiplying and so cannot cause illness to people. By using the adenovirus vector technology, a couple of problems with existing vaccines used to fight annual flu outbreaks are solved.
Problems with current influenza vaccines include that they are made from eggs, a process that can take as long as six months. The vaccine Mittal and his research team has developed isn't grown in eggs, making vaccine production much faster.
Additionally it would be difficult under normal conditions to produce the hundreds of millions of doses needed to protect everyone at risk for highly pathogenic forms of bird flu. With the beginning of a pandemic, since H5N1 decimates poultry populations, the egg supply needed to produce vaccines would be drastically cut.
The new vaccine uses an adjuvant, molecules added to the vaccine that stimulate the body's immune system, so that lower doses of the vaccine can be used. The adjuvant also allows the vaccine to be stockpiled so more people can be vaccinated, and it helps the vaccine protect against variant forms of the H5N1. The only FDA-approved H5N1 vaccine protects against only that specific strain of flu and only works in about 60 percent of those immunized with a high dose.
"Adenoviral vector-based pandemic vaccines are an attractive option for developing countries where egg-independent cell-based vaccine technologies for other vaccines already are available," Sambhara said. "Since this process is already in place, our vaccine could be produced locally at an affordable price."
Since H5N1 has been known, it has changed so that there are now two main subgroups, called clades. Within one of the clades, five subcl
|Contact: Susan A. Steeves|