Pertussis, the highly contagious disease also known as whooping cough, has become a growing problem in adolescents in recent years despite its history as primarily a disease of infants and young children, federal data show.
“Even though the highest rate of pertussis is still among children under 6 months of age, the highest proportion of cases is now among adolescents,” said Dr. Amanda Cohn, an epidemic intelligence service officer for the Atlanta-based U.S. Centers for Disease Control and Prevention (CDC).
Dr. Cohn is one of the authors of a report titled “Pertussis — United States, 2001-2003,” published in the CDC’s Morbidity and Mortality Weekly Report that was released last week.
The study showed that reported cases of pertussis increased from a historic low of 1,010 in 1976 to 11,647 cases in 2003.
“A large increase in reported cases has occurred among adolescents” as vaccinations they received as young children have lost effectiveness, the authors wrote.
The report showed that nearly 29,000 pertussis cases were reported to the National Notifiable Disease Surveillance System from 2001 to 2003. Of that total, 6,608 cases, or 23 percent, involved children younger than 1, of which 5,872 were 6 months or younger.
Meanwhile, 9,609 pertussis cases, or one-third of all those reported, occurred among patients ages 10 to 19. About 6,800 cases were reported among Americans 20 or older, who accounted for 23 percent of the total.
Guidelines call for five doses of pertussis vaccine by a child’s sixth birthday.
“Infant/childhood vaccination has contributed to a reduction of more than 90 percent in pertussis-related morbidity and mortality since the early 1940s in the United States” because infants are the population likeliest to die or to suffer severe effects, the report states.
A “substantial increase” in cases involve preadolescents and teenagers, who become susceptible about six to 10 years after receiving their childhood vaccinations, the authors pointed out.
They found reason to hope the situation will improve. In June 30, the CDC’s Advisory Committee on Immunization Practices recommended pertussis booster shots for everyone ages 11 to 18.
“Preferably, youngsters should be getting these boosters at 11 or 12 years,” Dr. Cohn said.
The advisory committee issued its recommendation shortly after the Food and Drug Administration licensed a vaccine called Tdap, which combines protection against pertussis, tetanus and diphtheria, for that older age group.
Pertussis is a bacterial illness marked by fits of coughing, vomiting after coughing and, particularly in young children, a whoop when they exhale.
Dr. Cohn said “prolonged coughing” is the main symptom in adolescents who contract the disease. Because pertussis is highly contagious, teens are also at risk because of their extensive social contacts, she noted.
The report in the CDC journal found that the overall average annual incidence of pertussis during the study period was 3.3 cases per 100,000 population. The figure rose from 2.7 per 100,000 in 2001 to 4.0 per 100,000 in 2003.
By age group, average annual incidence was highest (55.2 per 100,000) among those age 1 or younger. Within that group, incidence was 98.2 per 100,000 in babies younger than 6 months.