Bookmarkers beware: Bookmarks to pages other than the home page may not work after we change servers in April Editor's Choice | This Week in BMJ | Press releases BMJ No 7125 Volume 316 News Saturday 10 January 1998 Dutch whooping cough epidemic puzzles scientists Dutch scientists are struggling to identify the exact cause of an epidemic of whooping cough that has swept through the country despite vaccination rates as high as 96%. Similar problems are also being reported from Norway and Denmark. The incidence of whooping cough in the Netherlands had been relatively low, but reported cases increased from 321 in 1995 to 2,778 (18 per 100,000 population) in 1996. By the end of November last year 3,747 cases had been reported. Reports have been widespread, with no clustering in areas of low vaccination. Neither has evidence been found for a similar increase in whooping cough in Belgium near to the Dutch border. Latest figures show that the epidemic is abating, though it is feared that the underlying level is still too high.   A mutated strain of Bordetella pertussis has emerged Photo: NIBSC/SCIENCE PHOTO LIBRARY Epidemic cycles are expected every three to five years - this latest epidemic has come early. Medical microbiologist Joop Schellekens of the National Institute of Public Health and the Environment said: "We still do not know the cause. We can only speculate on likely factors." Though the incidence is still relatively low, he said: "It is the principle which worries us. We cannot understand why this happens and it may have consequences for the future." He denied reports that the epidemic was solely the result of the emergence of a mutated strain of the bacterium Bordetella pertussis. Scientists have found an increasing incidence of strains of B pertussis with a mutated surface protein, pertactin - so called B and C strains. But at present no proof exists that the mutations affect the immunity induced by the Dutch vaccine. Dr Schellekens argues that the new strains emerged in the 1980s and are likely to be found in other countries, not just the Netherlands. The Dutch ministry of health instructed the National Institute of Public Health and the Environment to check the quality of the whole cell vaccine that it produced. The institute has established that the Dutch vaccine produces a mixed antibody response to the different virulence factors, which compares unfavourably with vaccines used in Britain and France. An improved vaccine was quickly introduced in November. It is hoped that improvements in the way the Dutch vaccine is produced will broaden its immunogenicity profile. The institute is also conducting research into the possibility of introducing an additional acellular booster vaccine programme for all 4 year olds. Dr Schellekens said that the epidemic has shown that "even in a highly vaccinated population, pertussis keeps on circulating, which opens the possibility of long term antigenic changes." This was not yet "an established fact but needs to be monitored." Meanwhile Norway's National Institute of Public Health has reported a "dramatic increase" in notifications despite vaccination coverage of 85-90%. The incidence of whooping cough increased from 2.1 per 100,000 population in 1996 to 26.8 by the last week of 1997, a total of 1,158 cases. In addition, figures from Denmark's Statens Serum Institute, in Copenhagen, show 70 notifications in the first half of 1997, compared with 25 for the same period in 1996. Tony Sheldon Utrecht Home | Current issue | Past issues | Classified ads | Career Focus | Feedback Collections | About this site | About the BMJ | BMA | Medline