Updated: December 14, 2006
Pertussis or whooping cough is a bacterial infection caused by Bordetella pertussis, which infects only humans. Pertussis is an illness of prolonged, often severe, coughing spells; it is often marked by a “whoop” when the person gasps for air. It is most severe when it occurs early in life. Most of the deaths due to pertussis occur in infants.12
Routine immunization of infants and young children with pertussis-containing vaccines since the 1940s led to a dramatic decline in the number of cases and deaths due to pertussis.3
However, pertussis cases among adolescents, adults and young infants were increasingly recognized during the 1980s. These trends continued in the 1990s with increasing numbers of cases and deaths. A disproportionate number of the deaths have been in infants younger than four months of age—too young to have been protected by immunization. (1) Canada has seen similar phenomena.4
In 1997, adolescents and adults accounted for almost half of the reported cases of pertussis; they are often the ones who spread the disease to young infants. The rise of adolescent and adult pertussis is likely the result of waning immunity over time—which occurs both after natural infection and after immunization. This has prompted consideration of booster pertussis immunizations for older age groups.56
In 2003, over 11,000 cases of pertussis were reported in the US—of these, 40% were in individuals 10 to 19 years of age.7
However, many pertussis cases could go undiagnosed, because it is difficult to recognize pertussis symptoms in adolescents—they often do not exhibit the classic ‘whoop’ of the disease in children. Although the first symptoms mimic a cold, pertussis can lead to severe cough episodes lasting up to 100 days. Severe coughing episodes can lead to vomiting, a hernia or a broken rib.8
Adolescents rarely die from pertussis, but it poses a great risk to those whom they expose who are unvaccinated. The disease will develop in 90% of unvaccinated children living with someone with pertussis. Studies of adolescents and adults with prolonged coughing illnesses (1-2 weeks or longer) report that between 12% and 32% of the cases are caused by B. pertussis.9 Approximately 50 out of every 10,000 people who develop pertussis die from the disease, most being young infants.
The pertussis vaccines licensed in the United States are combination vaccines containing tetanus and diphtheria toxoids; some are combined with other vaccines as well. These vaccines are abbreviated DTaP for the vaccines given to children under 7 years of age. Some of the DTaP vaccines have been combined with other vaccines so as to reduce the number of injections that must be given to young children. The dose of diphtheria toxoid in vaccines given to persons seven years of age and older contains lower amounts of diphtheria toxoid than that which is given to younger children. Thus, the combined diphtheria and tetanus toxoids which has been used for many years as a booster dose is abbreviated Td, to reflect the lesser amount of the diphtheria component. But these products contain no pertussis vaccine.
Two new vaccines were licensed by the Food and Drug Administration for use in older individuals in 2005. These vaccines are abbreviated Tdap. One, BOOSTRIX®, is licensed for use in persons 10-18 years of age, the other ADACEL® is licensed for use in persons 11-64 years of age.
Recommendations for the use of these newly licensed vaccines have recently been published:
Recent studies4511 have examined the costs and benefits for a number of different strategies to immunize adolescents and adults with a Tdap vaccine. These studies examined cases of pertussis that could be prevented, the costs of cases of pertussis, and the lives that could be saved. For example, one study found that universal immunization of adolescents 10-19 years of age would be expected to prevent between 400,000 and 1.8 million cases among vaccinated adolescents and would save between $1.3 and 1.6 billion. Selective immunization of adolescents and young adults who are likely to care for young infants would also be cost saving.5 Similarly, universal immunization of 12 year olds in Canada is also expected to be cost saving.4
Currently, the diphtheria-tetanus-acellular pertussis (DTaP) vaccine is indicated for children younger than 7 years of age. No pertussis-containing vaccine is currently licensed in the United States for children 7-9 years of age