"Prevnar has done a remarkable job. Over the last seven years, it's prevented thousands and thousands of infections," not just in vaccinated kids but also in unvaccinated family members, said the CDC's Whitney.But it is a unique vaccine because it covers only seven of the 90-odd strains of the germ. By contrast, measles is caused by one type of virus. Booster shots are needed for chickenpox, mumps and measles because immunity wanes, not because the germ changed.Prevnar, however, is losing its punch because strains not covered by the vaccine are filling the biological niche that the vaccine strains used to occupy, and they are causing disease.
One strain in particular, called 19A, is big trouble. A new subtype of it caused ear infections in the nine Rochester children, ages 6 months to 18 months, that were resistant to all pediatric medications, said Dr. Michael Pichichero, a microbiologist at the University of Rochester Medical Center.The children had been unsuccessfully treated with two or more antibiotics, including high-dose amoxicillin and multiple shots of another drug. Many needed surgery to place ear tubes to drain the infection, and some recovered only after treatment with a newer, powerful antibiotic whose safety in children has not been established.Pichichero refused further comment because he has submitted a report to a medical journal. His work was paid for by antibiotic maker Abbott Laboratories and the Thrasher Foundation, which funds projects related to child health.All 19A strep subtypes tend to be resistant to some drugs and have been growing in prevalence:
—Scientists from a drug company and two labs analyzed more than 21,000 bacterial samples from around the nation and found 19A increasing. Among children 2 and under, the portion of samples that were this strain rose to 15 percent in 2005-2006, from 4 percent in the previous three years.
—A British lab tracking respiratory infections in U.S. kids found that the 19A strain accounted for 40 percent of drug-resistant cases.
—University of Iowa researchers found 19A accounted for 35 percent of penicillin-resistant infections in 2004-05, compared with less than 2 percent the year before the new vaccine came out.
Because these bacteria easily swap gene components to become even more hardy, "new types may emerge that can both escape containment by vaccine and spread throughout the world," Dr. Daniel Musher of Baylor College of Medicine wrote in the New England Journal of Medicine last year.Some think Prevnar might be destined to be like flu shots that must be periodically updated to reflect new strains causing illness. But each tweak requires new safety studies and more expense.Wyeth expects to finish testing its updated vaccine next year and to seek federal approval in early 2009. Review can take a year or more, Paradiso said.British-based GlaxoSmithKline has a similar vaccine in final-phase testing that targets 10 strains common in Europe and other regions.
As in the days of Noah...