An acellular vaccine contains on parts of the cells which can produce immunity in a person receiving the vaccine.
The acellular pertussis vaccine appears to greatly reduce the risk of unpleasant reactions to the vaccine, including high fever and discomfort following vaccination.
A so-called "acellular pertussis" vaccine (aP) is usually used since its release in the mid-1990s.
The vaccine used in the United States is actually multiple diphtheria and tetanus toxoids combined with acellular pertussis (DTaP).
Diphtheria and tetanus toxoids and acellular pertussis, taken together, provides immunity against diphtheria, tetanus, and whooping cough.