This may be because of improved vaccine technology and using only portions of the organism rather than the entire bacterium. (shirleys-wellness-cafe.com)
These individuals are particularly susceptible to the more serious effects of influenza infection, so improving vaccine efficacy in these people would be a real plus. (sciencemediacentre.org)
In hope of further improving the vaccine, the researchers are now examining why it works in only about half of the vaccinated monkeys. (nih.gov)