Effectiveness of pertussis vaccine decreases from 1996-2001 in Poland.

2004 MAY 5 - (NewsRx.com & NewsRx.net) -- The effectiveness of vaccination with a whole-cell pertussis vaccine decreased in Poland from 1996 to 2001.

According to recent research published in the Scandinavian Journal of Infectious Diseases, "Recurrence of pertussis in highly vaccinated populations has been observed in many countries. Two mechanisms have been proposed to explain it: a shift in incidence towards older age groups in which the protective effect of vaccination is diminished; and vaccine-induced changes in genomic and immunological characteristics of circulating strains of Bordetella pertussis, which become different from vaccine strains, thereby reducing vaccine efficacy.

"Marked increase in the incidence of pertussis has been observed in Poland since 1997, following a decade of stability at a low level," said Andrzej Zielinski and colleagues at the National Institute of Hygiene in Warsaw. "As previously shown, the immunization calendar in Poland does not ensure sufficient protection among children older than 9 years. The decrease in the protective effect becomes noticeable after the age of 5. In this paper we examine changes in the effectiveness of pertussis vaccination in four age groups during 1996-2001, using surveillance data.

"We find that over that period a decrease ...