Sero-epidemiology of Bordetella pertussis in England and Wales.

The incidence of pertussis infection can be estimated in the population by defining a single high titre of anti pertussis toxin (PT) immunoglobulin G (IgG) antibody predictive of recent infection. Sera samples collected in 1986, 1996 or annually between 1987 and 1998 were tested for anti-PT IgG antibody. In 1996, the age-adjusted prevalence of pertussis infection was 1.2% and was higher in children than in adults. Amongst samples collected annually, older age and female sex, but none of the temporal variables, were associated with a serologically defined pertussis infection. There is an important incidence of infection in the population, which is greater amongst children than adults, but there is only limited evidence of a correlation with epidemic cycles.