Whooping cough, or pertussis, is a highly contagious respiratory disease caused by the bacterium Bordetella pertussis. It manifests with severe coughing fits, often followed by a characteristic “whooping” sound. Before the advent of vaccination, pertussis posed a considerable threat, particularly to infants and young children, leading to widespread illness and fatalities. Its historical impact underscored the urgent need for an effective preventive measure.
The Whole-Cell Vaccine Emerges
The journey to a whooping cough vaccine began with the isolation of Bordetella pertussis by Jules Bordet and Octave Gengou in 1906. Early, crude whole-cell pertussis vaccines were licensed in the United States by 1914, though they were not yet widely adopted for routine use. Significant progress occurred in the 1930s through the work of bacteriologists Pearl Kendrick and Grace Eldering at the Michigan Department of Health.
Kendrick and Eldering refined methods for growing the pertussis bacterium. Their efforts culminated in the first large-scale clinical trial of a pertussis vaccine conducted between 1934 and 1937. This research led to Michigan beginning production and distribution of their vaccine around 1940, which substantially reduced deaths from whooping cough.
The whole-cell vaccine was developed from inactivated Bordetella pertussis bacteria, meaning it contained the entire, but killed, bacterial cell. Kendrick and Eldering combined the pertussis component with diphtheria and tetanus toxoids, leading to the development of the diphtheria-pertussis-tetanus (DPT) vaccine. This combined vaccine was released around 1948 or 1949. Its widespread adoption contributed to a significant decline in pertussis cases and associated deaths, with reported cases in the U.S. falling from hundreds of thousands annually to a few thousand by the 1980s.
The Shift to Acellular Vaccines
Despite its effectiveness, the whole-cell pertussis vaccine was associated with notable side effects. Common reactions included redness, swelling, soreness, and fever. More severe, though less frequent, reactions like febrile seizures were also reported. These concerns, which gained public attention in the 1970s and 1980s, spurred research into a safer alternative.
Scientists embarked on developing an acellular pertussis vaccine in the late 20th century. Unlike its predecessor, this newer vaccine uses only specific, purified components of the B. pertussis bacterium, rather than the entire inactivated cell. These components often include detoxified pertussis toxin, filamentous hemagglutinin, and pertactin. Japan introduced the first acellular pertussis vaccine for use in 1981.
The acellular vaccine demonstrated a reduced incidence of adverse effects compared to the whole-cell version. This improved safety profile led to its gradual introduction and replacement of the whole-cell vaccine in many countries. In the United States, the Diphtheria, Tetanus, and acellular Pertussis (DTaP) vaccine was licensed for infant use in 1996. By 1997, the Advisory Committee on Immunization Practices (ACIP) recommended DTaP to replace DPT for the primary childhood vaccination series.
Contemporary Vaccination Practices
Current vaccination guidelines incorporate the acellular pertussis component within combination vaccines. Infants and young children receive the DTaP vaccine as part of a routine series. This schedule involves five doses administered at specific ages: two, four, and six months, followed by booster doses between 15-18 months, and again between four and six years of age.
Beyond childhood, booster shots are important to maintain protection against whooping cough. Adolescents receive a booster dose of the tetanus, diphtheria, and acellular pertussis (Tdap) vaccine, around 11 or 12 years of age. Adults are also advised to receive a Tdap booster every ten years to sustain immunity.
The Tdap vaccine is important for preventing the spread of pertussis, especially to infants too young for full vaccination who are at highest risk for severe complications. Pregnant women are recommended to receive a Tdap vaccine during each pregnancy, preferably in the early third trimester, to pass protective antibodies to their newborns. This strategy provides early protection to the most vulnerable population.