Acellular pertussis vaccines came into widespread use in the United States in 1997, when they were recommended by the Advisory Committee on Immunization Practices for the full immunization series starting in infancy.1 Acellular vaccines were seen as a safer alternative to whole-cell vaccines that had been in use since the late 1940s. Recently, however, provisional data from the Centers for Disease Control and Prevention list 41,880 cases of pertussis in calendar year 2012, up from 18,719 in 2011.2 Incidence rates rival those seen in the prevaccine era, although comparisons with previous decades might be misleading due to better detection methods with polymerase chain reaction (PCR) testing in recent years. Currently, Washington state leads the nation with 4604 provisional cases in 2012, compared with 962 in 2011, reflecting an epidemic in the state that began in mid-2011.3 Reasons for this upswing are multiple, but waning immunity of acellular pertussis vaccines likely is a key factor that will drive changes in immunization practices. Increases in pertussis rates in children aged 7 to 10 years and 13 to 14 years suggests that immunity after acellular pertussis vaccination wanes much sooner than hoped.
Journal: Clin Ther 2013