Overall, filibustering and U.S. policies seem to have hindered more than helped U.S. attempts at territorial expansion in this time period. The Gadsden Purchase was the only official territorial acquisition during the 1850s.
Acellular pertussis vaccines were introduced nation-wide in Sweden in 1996, 17 years after the withdrawal of whole-cell pertussis vaccine from the childhood immunisation schedule.he annual incidence of culture-confirmed B. pertussis was 89-150 per 100,000 before introduction of acellular pertussis vaccines and has dropped to 17-26 per 100,000. The data suggest that unimmunised infants and children who have received only one dose of pertussis vaccine were provided some protection.
The bacterium responsible for the infection, Bordetella pertussis, was not identified until 1906. In the pre-vaccination era (during the 1920s and '30s), there were over 250,000 cases of whooping cough per year in the U.S., with up to 9,000 deaths. In the 1940s, the pertussis vaccine, combined with diphtheria and tetanus toxoids (DTP), was introduced. By 1976, the incidence of whooping cough in the U.S. had decreased by over 99%.