Pertussis re-emerges in Netherlands despite hi vax coverage

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"Adaptation of Bordetella Pertussis to Vaccination: A Cause for
Its Reemergence?"
Emerging Infectious Diseases Online (www.cdc.gov/ncid/eid)
(06/01) Vol. 17, No. 3,; Mooi, Frits R.; van Loo, Inge H.M.;
King, Audrey

Despite high vaccination coverage, pertussis has re-emerged in
the Netherlands, and researchers suggest that one possible cause
of this may be the adaptation of Bordetella pertussis to the
vaccine.  This theory was tested by characterizing B. pertussis
strains collected in the country between 1949 and 1996 using DNA
fingerprinting and sequencing genes coding for surface proteins.
There were significant differences between the populations in the
prevaccination era and after vaccination, in terms of the type
and frequency of fingerprint types.  The researchers also noted
that while there was little polymorphism in the majority of the
proteins studied, pertussis toxin and pertactin--two virulence
factors--were polymorphic and the antibodies against them were
linked with protection against disease.  Researchers found fewer
vaccine-type pertactin variants in vaccinated people compared to
unvaccinated people, "which would be expected if the vaccine
protects differentially against strains with distinct pertactin
types," the researchers said.  In conclusion, the researchers
recommend continued strain observation, particularly as
whole-cell vaccines are being replaced by acellular ones in some
countries.

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