Tdap recommendations causing some confusion

December 2006

NEW YORK – The approval of two formulations of the tetanus toxoid and reduced diphtheria toxoid and acellular pertussis vaccine and subsequent recommendations this year by the Advisory Committee on Immunization Practices for their use in adolescents and health care workers have led to some confusion about who should receive what vaccine when.

“We’re getting a lot of reports where Tdap has been given to children inappropriately,” said Larry K. Pickering, MD, director of the National Center for Immunization and Respiratory Diseases of the CDC. DTaP (diphtheria and tetanus toxoids and acellular pertussis) vaccine is recommended for all infants at 2, 4 and 6 months of age. An additional dose of DTaP vaccine is recommended at 15 to 18 months of age and at 4 to 6 years of age.

However, last year, two Tdap products were approved Boostrix, by GlaxoSmithKline, and Adacel, by Sanofi Aventis for use in adolescents.

In June 2005, the ACIP recommended that adolescents aged 11 and 12 years receive Tdap – either product – in place of the Td booster. The committee also recommended that adolescents aged 13 to 18 who missed the 11- to 12-year dose of Td receive Tdap.

Subsequent recommendations for the vaccine’s use were released this year.

In the 11 to 64-year-old age group, health officials recommend giving a single dose of Tdap instead of Td for a booster. For people 11 to 64 years of age who received diphtheria toxoid, a five-year minimum is encouraged between receiving Td and Tdap. However, recently presented data by Scott Halperin, et al, who showed that physicians could knock that minimum requirement down to two years if pertussis was in the community, Pickering said.

According to recommendations from the ACIP earlier this year, Tdap is indicated for health care workers who work in hospitals or ambulatory care settings and have direct patient contact as soon as feasible if they have not previously received vaccine.

Getting vaccinated is important, particularly for health care workers, Pickering said, because approximately 60% of pertussis cases occur in adolescents and adults older than 20. Physicians, nurses, medical and nursing students and primary care providers are among the estimated 8 to 10 million health care workers recommended for the vaccine. The ACIP recommended that health care workers who do not work in hospitals or ambulatory care settings, or do not have direct patient contact, receive Tdap according to the adult vaccine recommendations.

Pickering said that pertussis is the only vaccine-preventable illness where the rates of illness have climbed in recent years.

Vaccine approval

He said that the approval of diphtheria and tetanus toxoids (DTP) vaccine had a dramatic effect on the rate – he showed a slide that illustrated huge decreases between 1922 and 2004.

According to the CDC, an average of more than 160,000 cases and more than 5,000 deaths were reported every year in the 1920s to 1930s. At its peak during this period, the annual number of case-reports was more than 250,000 with up to 9,000 deaths. In the 1940s, whole-cell pertussis vaccine combined with DTP was introduced, and case-reports of pertussis decreased more than 99% by 1976, when the number of reported cases reached a record-low of 1,010 cases. However, in recent years, the numbers have started to tick upwards, in 2005, there were about 26,000 cases of pertussis in this country, most of which were in young adults.

“Why have we seen this more recently, I think one reason is increases in diagnostic capabilities,” Pickering said. “There is an increased recognition of symptoms, and enhanced case reporting is helping.” Also, he said, the vaccine-induced immunity wanes, adding that many people who haven’t had the vaccine are probably susceptible to pertussis.

He cited an article that appeared in the Annals of Internal Medicine (Dworkin. 2005;142:832) that noted “pertussis is not a ‘zebra’ diagnosis, but deserves a place among the community-acquired list of adult pathogens.”

Recognizing pertussis

To help physicians recognize these cases, Pickering reviewed the causes and symptoms that pediatricians will commonly see in these patients.

Pertussis is a bacterial respiratory illness is caused by the bacterium Bordetella pertussis, a very small Gram-negative aerobic coccobacillus that appears singly or in pairs.

The disease has two stages, colonization and toxemic.

During the first stage, the B. pertussis organism can be recovered in large numbers from pharyngeal cultures, and disease severity and duration can be reduced by antimicrobials. The binding mechanims of B. pertussis involves a filamentous hemagglutinin, which is a fimbrial-like structure on the bacterial surface, and cell-bound pertussis toxin (PTx). Short range effects of soluble toxins play a role as well in invasion during the colonization stage.

During the second stage, the illness is characterized by severe spasms of coughing that can last for several weeks or even for months. Pertussis is usually spread from person-to-person through close contact with respiratory droplets released when a person coughs or sneezes.

Pickering said that the illness is associated with difficulty breathing and sleeping, and some uncommon comorbidities, such as pneumonia, rip fractures and apnea.

For more information:

• Pickering LK. Adolescent immunizations: Many dilemmas. Presented at: 19th Annual Infectious Diseases in Children Symposium. Nov. 18-19, 2006. New York.