Vaccines delivered via droplets rubbed into the skin appear to protect against ear infections, say researchers who tested the method on

chinchillas.If this approach proves effective in humans, it could provide a simple, inexpensive way of preventing ear infections, the researchers noted.

Three groups of chinchillas had droplets of the vaccines rubbed into the skin of their ears once a week for three weeks. A fourth group received a placebo. After receiving the vaccines or placebo, the animals were infected with nontypeable haemophilus influenzae (NTHi), one of the three main bacterial causes of otitis media, an infection/inflammation of the middle ear.

The chinchillas that received the vaccines were able to very rapidly reduce, or eliminate NTHi from their nose and ears, but this wasn't the case in the animals that received the placebo. The findings were presented May 21 at the American Society for Microbiology annual meeting, in Philadelphia.

"Our data are the first to show that transcutaneous immunization is an effective way to prevent experimental ear infections and lays the foundation for an effective, yet simple, inexpensive -- and potentially transformative -- way to deliver vaccines," Laura Novotny, of the Research Institute at Nationwide Children's Hospital in Columbus, Ohio, said in a news release.

"We have designed several vaccine candidates which target proteins on the outer surface of this bacterium [NTHi]. Previous work in our lab showed that after immunization by injection, each of the three vaccine candidates prevented experimental ear infections caused by NTHi. In this study, we now wanted to test an alternative but potentially equally effective method to deliver a vaccine," Novotny said.

It is estimated that up to 83 percent of children in the United States will have at least one ear infection by the time they're 3, according to the news release.