1.   In contrast to the old vaccines, which used a killed whole cell of pertussis bacteria, the new so-called acellular vaccines use only pieces of the cell.

2.   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.

3.   This vaccine uses a whole cell of pertussis bacteria that is inactivated, usually with heat.

4.   Recent studies have suggested that the varieties of the pertussis bacteria in circulation today are different than they were in the past.

5.   The new vaccine is based on a protein made by the pertussis bacteria that usually causes toxic symptoms -- the classic coughing and fever of whooping cough.

6.   The new vaccine uses only parts of the pertussis bacteria to prompt the body to become immune.

7.   Blood tests confirmed the presence of the pertussis bacterium in those with coughs that lasted at least two weeks.