In many countries, the prevalent serotypes of Bordetella pertussis have changed from a mixture of types 1,2,3 and 1,2 (organisms possessing antigen 2) to a predominance of type 1,3. The timing of the change in different countries is shown to be related to the introduction of mass-vaccination with material rich in antigens 1 and 2 but weak in, or devoid of, antigen 3. In several parts of the world, there have been outbreaks of type 1,3 infection in fully vaccinated children.
Non-vaccinated communities in various parts of the world still show the pattern of serotypes which existed elsewhere before mass-vaccination.
In order to avoid the disappointments experienced in the past, it is essential that pertussis vaccine for use in previously non-vaccinated communities, like that for any other country, should be rich in each of the three antigens.