When not treated, strep can cause rheumatic fever, a mysterious illness that occurs in as many as three out of 100 untreated strep cases.
The fever often damages the heart, which typically fails when victims are in their 20s or 30s. An estimated 16 million to 20 million people around the world have rheumatic heart disease, and a half-million people die annually, according to the World Health Organization.
"It's a nasty, nasty bug. Strep is a devastating organism," said microbiologist Vincent Fischetti, a professor at Rockefeller University in New York City. "It's always been everyone's dream to get a vaccine."
While he praised Dale's work, Fischetti also expressed concern that the vaccine might not work for all strains of the bacteria.
Other strains of strep
The latest version of Dale's vaccine targets the 26 most prevalent M proteins. But there are more than 150 overall, and Fischetti suspects that Dale's vaccine could leave many people unprotected, particularly outside the United States. Foreign strains of the bacteria are not as well understood and might be able to circumvent the vaccine.
Some other experts agreed. Dale's vaccine "will not protect against every strain and probably won't come close to that," said University of Minnesota microbiologist Patrick Cleary.
Fischetti and Cleary are working on vaccines of their own, taking different approaches. NIAID is also funding their work; Rubin, the program officer, said all three are promising strategies.
For her part, Kotloff preferred to focus on the positive results of the new study.
"I'm excited," she said. "We've opened a door that had been closed for many years."