Chicago ? A vaccine that has dramatically curbed pneumonia and other serious illnesses in children is having an unfortunate effect: promoting new superbugs that cause ear infections.

On Monday, doctors reported discovering the first such germ that is resistant to all drugs approved to treat childhood ear infections. Nine toddlers in Rochester, N.Y., have had the germ, and researchers say it may be turning up elsewhere, too.

It is a strain of strep bacteria not included in pneumococcal vaccine, Wyeth’s Prevnar, which came on the market in 2000. It is recommended for children under age 2.

Doctors say parents should continue to have their toddlers get the shots because the vaccine prevents serious illness and even saves lives. But the new resistant strep is a worry.

“The best way to prevent these resistant infections from spreading is to be careful about how we use antibiotics,” said Dr. Cynthia Whitney, chief of respiratory diseases at the federal Centers for Disease Control and Prevention.

Avoiding antibiotics when they are not needed is the best way to ensure they will work when they are, she said.

Prevnar prevents seven strains responsible for most cases of pneumonia, meningitis and deadly bloodstream infections. But dozens more strep strains exist, and some have flourished and become impervious to antibiotics since the vaccine combats the more common strains.

If the new strains continue to spread, “it tells us the vaccine is becoming less effective” and needs to be revised, said Dr. Dennis Maki, infectious diseases chief at the University of Wisconsin-Madison Hospitals and Clinics.

Wyeth anticipated this and is testing a second-generation vaccine. But it is at least two years from reaching the market, and the new strains could become a public health problem in the meantime if they spread hard-to-treat infections through day care centers and schools.

“I don’t think the new strains are moving fast enough to call it a race, but the fact is that certain strains are increasing,” said Peter Paradiso, a scientist at Wyeth Vaccines, the Collegeville, Pa., division that makes Prevnar.

“It is very worrying,” said Dr. Keith Klugman, an infectious diseases specialist at Emory University. “With the eradication of all the other types in the vaccine, this one is emerging.”

Several research teams reported on the situation Monday at microbiologists meeting.

A different pneumonia vaccine has long been available for adults but it doesn’t work in children, so Prevnar was hailed as a breakthrough. It is used in dozens of countries and had sales of more than $1.5 billion last year. In the United States, it is given as four shots between 2 months and 15 months.