Text Box: MASS VACCINATION AGAINST PERTUSSIS WITH A MONOCOMPONENT PERTUSSIS TOXOID VACCINE Taranger J, Knutsson N, Trollfors B, Bergfors E, Sundh V, Lagergard T, Zackrisson G, Lind- Brandberg L The Goteborg Pertussis Vaccine Study, The Goteborg Primary Health Care System, Goteborg, Sweden Objective: To evaluate if mass vaccination with a monocomponent pertussis toxoid vaccine decreased spread of Bordetella pertussis in a population which had not used effective pertussis vaccines. From 1979 through 1995 there was no vaccination against pertussis in Sweden. Methods: Mass vaccination of children born during the 1990s started in 1995 in the Goteborg area (population 778,597) of Sweden with pertussis toxoid after efficacy had been shown in a double-blind study (point estimate of efficacy 71 %). Infants were offered three doses of pertussis toxoid combined with diphtheria and tetanus toxoids. Children aged >1 year were offered 3 doses of pertussis toxoid alone. Results: From June 1995 through February 1999, 167,810 doses of pertussis toxoid were given to 61,219 children (56 % of all children born during the 1990s). The number of Bordetella pertussis isolates declined from 1,200 to 64 per year (P<0.0001) and hospitalizations due to pertussis from 62 to 4 per year (P<0.0001). Significant decreases in B.pertussis isolates and hospitalizations occurred in all age groups including nonvaccinated infants and adults. Conclusion: Vaccination of children decreased transmission of the causative organism and gave indirect protection against pertussis to nonvaccinated individuals. 1990