Avian Flu Vaccine

Earlier, someone asked why they couldn't just make next year (or this year's) influenza vaccine include H5N1, the avian flu

As this article explains:

The H5N1 bug first emerged in Hong Kong in 1997, but early efforts to make a vaccine against it didn't work well. Researchers concluded they had used the wrong strains of the virus, partly because they couldn't get more dangerous varieties to grow in the laboratory.

To get around this problem, vaccine makers use vaccines that do grow well in the lab and use genetic engineering to replace the most important genes of the virus (from a vaccine standpoint) with their avian flu counterparts.

This is a bit risky, since you can't be as sure the vaccine will work, but even more importantly, takes time.