  The recent increase in Bordetella pertussis incidence (whooping cough)
presents a challenge to global health. Recent studies have called into question
the effectiveness of acellular B. pertussis vaccination in reducing
transmission. Here we examine the epidemiological consequences of an
ineffective B. pertussis vaccine. Using a dynamic transmission model, we find
that: 1) an ineffective vaccine can account for the observed increase in B.
pertussis incidence; 2) asymptomatic infections can bias surveillance and upset
situational awareness of B. pertussis; and 3) vaccinating individuals in close
contact with infants too young to receive vaccine (so called "cocooning"
unvaccinated children) may be ineffective. Our results have important
implications for B. pertussis vaccination policy and paint a complicated
picture for achieving herd immunity and possible B. pertussis eradication.
