The rise in pertussis cases urges replacement of chemically-inactivated with genetically-inactivated toxoid for DTP

The number of pertussis cases reported to the CDC increased from 5158 in 1995 to 21,503 in 2005. Most of the increase was in individuals greater than 10 years of age. This increase occurred also in other developed nations despite high coverage of infants and young children with the acellular pertussis vaccine. In Goteborg Sweden, virtual elimination of pertussis occurred following immunization of 70% of the children less than 10 years old with monocomponent pertussis toxoid (PTx). Immunity following disease or vaccination with either the cellular or acellular pertussis vaccine wanes gradually so that older children and adults may again become susceptible. Currently, PTx is made from chemically-inactivated pertussis toxin (PT). The most immunogenic PTx is made from genetically-inactivated mutant PT that induces higher levels of IgG anti-PT at all ages. Because of its greater immunogenicity, the genetically-inactivated PTx can be expected to be more protective on an individual and on a community basis for a longer duration than the current product. Manufacturers have declined to produce the genetically-inactivated PTx because of the expense required to change to the improved vaccine and not because of scientific issues.