A Harvard physician has developed a vaccine that could prevent thousands of babies each year from acquiring Group B streptococcus, a potentially deadly infection.

Group B streptococcus is a bacterium present in many women's bodies.

It is harmless, but can be fatal or brain-damaging if passed to infants in the birth canal.

"We know exactly what the vaccine should look like and how to make it," Channing Professor of Medicine Dennis Kasper told the Associated Press. "Now it's a matter of going through the testing...so it can save babies' lives."

The National Institutes of Health (NIH) will test the new vaccine during the next year to prove that it is safe enough and works well enough to administer.

Approximately 30 percent of American women have Group B strep. Of the 4 million babies born each year, about one in 500 are infected with Group B strep.

It is fatal about 10 percent of the time, and nearly 50 percent of Group B strep infants suffer long-term damage ranging from seizures to mental retardation as a result of the infection.

Dozens of other babies catch a slightly less fatal "late-onset" form of Group B strep from less intimate contact with infected adults when they're several weeks old.

Last spring, the Centers for Disease Control and Prevention (CDC) advised obstetricians to give penicillin to all women at risk for strep when they give birth.

More than 1 million women may get treated every year, but the treatment is effective only about 85 percent of the time, according to the CDC.

The vaccine developed by Kasper prompts the mothers' immune systems to send antibodies across the placenta and provide newborns with strep protection for a few months until the babies' own immune systems begin functioning.

Kasper created the vaccine using the sugar coating that encapsulates Group B strep, enabling the body to recognize the bacteria without developing the disease.

The first attempt at the vaccine proved safe but was too weak to prevent strep. Kasper then added a version of the tetanus vaccine to his initial strep vaccine to boost its effectiveness.

In a study in this month's Journal of Clinical Investigation, Kasper gave 100 Houston women who were not pregnant either the strengthened vaccine or the old, weaker one.

More than 90 percent of women who received the new vaccine produced significant antibodies against strep while only about 60 percent of women who received the old vaccine did.