A study of the effectiveness of the acellular vaccine during a pertussis outbreak in California found widespread disease among fully vaccinated older children, with attack rates markedly increasing 3 years after vaccine dose. The finding suggests that the current schedule of vaccine doses provides inadequate protection or durability. The study analyzed electronic medical records of 171 patients with a positive polymerase chain reaction (PCR) test for Bordetella pertussis during 9 months of 2010, including 132 pediatric patients, and found that there was a notable increase in cases in patients aged 8 to 12 years, proportionate to the interval since the last scheduled vaccine. The rate of testing peaked in infants but remained relatively constant until 12 years. The rate of positive tests was low for children aged zero to 6 years and increased in preadolescents, peaking at 12 years. Vaccination rates of preadolescents who were PCR-positive were approximately equal to that of controls.
Source: Contemporary Pediatrics Staff. Modern Medicine