11.   The so-called acellular pertussis vaccines use only a piece of the pertussis bacteria, thereby gaining the benefit of immunization without as many side effects.

12.   The two companies say they hope to supplant their whole-cell pertussis infant vaccine with their new versions.

13.   When I have a burning question on acellular pertussis vaccine, I turn to them for an update.

14.   Another type of pertussis vaccine is used after that age, she said.

15.   The controversy prompted National Institutes of Health scientists to develop a pertussis vaccine that protected against the disease without the danger of side effects.