VACCINES TO PREVENT CHILDHOOD EAR INFECTIONS UNDER DEVELOPMENT

COLUMBUS, Ohio -- Researchers studying ways to prevent middle ear infections in children have developed some promising candidate vaccines, according to an Ohio State University expert.

"Earlier vaccines proved ineffective against acute middle ear infections. However, newer vaccines have been shown to be possibly effective," said Lauren O. Bakaletz, associate professor of otolaryngology at Ohio State.

"The newer vaccines have much better prospects for success in clinical trials."

Bakaletz co-authored a recent review article on the prospects for a childhood vaccine against middle ear infections -- medically known as otitis media.

Although progress has been made in developing vaccines, parents should not expect a breakthrough in the immediate future, Bakaletz said. "Parents looking for some relief are going to be suffering with the antibiotics and ear tubes for a while longer," she said. "However, the science right now is encouraging. These

things can sometimes turn around quite quickly."

Middle ear infections are the leading reason for children under age 6 to visit a physician, Bakaletz said. In fact, she said, a study published last year found that virtually all American children will develop otitis media in their first year of life.

"In 1990, there were about 24.5 million cases of otitis media in the United States alone, and that reflected a 258 percent increase since 1977," Bakaletz said. "The cost in medical treatment and lost wages for parents is estimated at $6 billion per year. It's an enormous problem."

Bakaletz' co-authors on the review article are Pekka H. Karma, professor of otorhinolaryngology at Helsinki University Hospital (Finland); G. Scott Giebink, professor of pediatrics and otolaryngology at the University of Minnesota; Goro Mogi, professor of otolaryngology at Oita Medical University (Japan); and Britta Rynnel-Dagoo, professor of otorhinolaryngology at Huddinge University Hospital (Sweden). The group's article appeared in a recent issue of the International Journal of Pediatric Otorhinolaryngology.

Otitis media occurs when bacteria living in the nose and throat migrate to the middle ear through the Eustachian tube. Respiratory viruses, which compromise the Eustachian tube's ability to move bacteria and debris away from the middle ear, are a predisposing factor for the illness, Bakaletz said. Symptoms of otitis media may include a sense of fullness in the ears, pulling at the ears, impaired hearing, pain and fever.

Currently, there are two treatment options for children with middle ear infections -- placing them on antibiotics or placing pressure-relieving tubes in their ears. However, Bakaletz said, both options have shortcomings.

In some cases, antibiotic treatment for middle ear infection is only marginally effective, she said. "Physicians give kids antibiotics because they have few alternatives; studies have shown that antibiotics can be helpful in certain cases. However, once the middle ear gets infected, it can become a closed system. Antibiotics have a very hard time getting in there." Giving children more powerful, broader spectrum antibiotics heightens the chances of inducing antibiotic resistance, Bakaletz added.

The surgical option is equally problematic, she said. "Putting tubes in the ears involves putting a young child under general anesthesia. Plus, it's rather expensive."

These shortcomings -- and the fact that cases of otitis media peak when children are at their weakest immunologically -- motivated researchers to pursue the vaccine option.

"Peak incidence of middle ear infection occurs between age six to 12 months," she said. At this same age, a child's antibody levels are at their lowest. This suggests that, in addition to other factors, immunity may play a major role in the development of otitis media."

In the 1970s, researchers tested pneumococcal vaccines for effectiveness against otitis media in children. Streptococcus pneumoniae bacteria are thought to cause 50 to 60 percent of cases of otitis media. These vaccines worked relatively well with adults and older children, but were ineffective in preventing middle ear infections in infants.

Bakaletz says the failure of these vaccines lies in the fact that they contained only polysaccharide bacterial components -- components the infant immune system could not recognize.

Today's candidate pneumococcal vaccines against otitis media are what scientists call "conjugate" vaccines -- they have a polysaccharide component linked to a protein component the infant immune system can recognize.

These pneumococcal conjugate vaccines have been shown to protect chinchillas from middle ear infections, Bakaletz said. They've also been shown to be safe in adults, children and infants. "These vaccines are promising candidates for clinical trials against otitis media in infants," she said.

Vaccines targeting the other types of bacteria known to cause middle ear infections -- non-typable Haemophilus influenzae (NTHI) and Moraxella catarrhalis -- are being developed. However, these are not as likely to be tested in clinical trials in the near future, Bakaletz said. The pathogenic and immunologic properties of these bacterial species are not well understood, she said.

Vaccines to prevent the viral infections that predispose children to middle ear infections are also being developed. However, these, too, will take time to perfect. Viruses can change their surfaces, which stimulates the immune system to produce antibodies that are no longer effective, Bakaletz said.

Contact: Lauren O. Bakaletz, (614) 293-8103; Bakaletz.1@osu.edu

Written by Kelly McConaghy Kershner, (614) 292-8308;

Kershner.4@osu.edu


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