The incidence of pertussis (whooping cough) has risen dramatically in recent years reflecting the relative weak immunogenicity of the acellular vaccine compared with the prior whole-cell vaccine used prior to 1996. The vaccine is typically given as a combination known as Tdap (tetanus, diphtheria and acellular pertussis). To compensate for the reduced effectiveness of the acellular form, the Advisory Committee on Immunization Practices (ACIP) now recommends that adults and adolescents get booster shots to provide protection from infection. However, the booster has not lowered the incidence of the disease in neonates. The recommendation is supported by the American College of Obstetricians and Gynecologists (ACOG) except for women who have been previously vaccinated.