Soon, nasal spray flu vaccine for infants, elderly?

US researchers claim to have developed a method that could make a nasal spray flu vaccine effective for infants under the age of two and those over 49 - two groups for which the vaccine is not approved.
By studying the weakened flu virus that is the basis for the nasal spray vaccine in cells from human nasal and sinus cavities, the researchers said they have determined that the virus can be weakened (for young children) or strengthened (in older people) enough to create an appropriate immune response in people of all ages.
"We think we can use our molecular, rational design approaches to make a better flu vaccine for people who really need it," said study leader Andrew Pekosz at the Johns Hopkins Bloomberg School of Public Health.

Pekosz said he is particularly excited about being able to produce a better vaccine for older people since flu vaccines are less effective in people as they age and because those over the age of 60 are more likely to get the flu and more likely to suffer serious complications.
"We don't have a really good effective vaccine in the elderly. Even the injectable version doesn't work as well in that population. And they're the ones who need it the most," Pekosz said.
Children ages six months to two years can receive an injectable flu vaccine, but the nasal spray vaccine is recommended in kids between the ages of two and eight because it is believed to give better protection than the shot.

Pekosz used human nasal tract cells to study the weakened strain of the flu virus that is used in the nasal spray vaccine and compared its behaviour with that of the flu virus.

Using these nasal tract cells allowed the researchers to determine that the weakened flu virus behaved differently than previous research had suggested.
At the end of the life cycle of the weakened virus, virus-infected cells send out harmless, non-infectious particles that immune cells pick up and attack to create antibodies against an actual flu virus that could attempt to infect the body later.
This response, however, was not as robust as the researchers imagined.

To create the weakened flu strain contained in FluMist, the brand name of the nasal spray vaccine, nine mutations in the flu virus were made.
Researchers previously believed that only five of them were relevant to creating the spray's immune response, but Pekosz said his new research suggests that all nine may be important.
By making adjustments to those mutations, Pekosz believes that a stronger vaccine can be made without an increase in side effects. He said that a weaker one can also be made - one that still protects from flu - for children under two.
Pekosz's team is currently collaborating with MedImmune, the makers of the FluMist, to help develop a better vaccine based on these findings.

He said if all goes well, there could be a new vaccine to test within six to 12 months for both the oldest and youngest.