Tommy was an eleven-year-old boy who came to the office with his mother for his yearly physical. All went well until we neared the end of the visit, at which time he cautiously asked, "I don't need a shot, right? My next shot is when I am 15." There was a moment of silence that cut through the room and a look of terror filled his face. I explained that up until very recently Tommy's supposition would have been correct. But the American Academy of Pediatrics made a recommendation last year for a new vaccine to be given to 11-to-12-year-olds. Tommy just put his head down and sighed.
The new recommendation calls for a tetanus booster to be given at 11 or 12 years of age, which offers protection against pertussis or whooping cough. The reason for this new schedule is as follows: the old schedule of immunizations called for DPT to be given at two, four and six months of age. This was followed by a booster given at 18 months and again at five years. The DPT vaccine is to protect against diphtheria, pertussis and tetanus. After completion of this series of shots one could be assured of being fully protected against these diseases...for a while. The protection against tetanus would wane each progressive year. Therefore, a booster was given at 15 years of age as a matter of routine. This booster was Td and was meant to protect against tetanus only. The T stands for tetanus, and the small d stands for diphtheria.
The diphtheria portion of the vaccine is a small amount to help with the body's ability to boost the response for tetanus, not to necessarily protect against diphtheria. It was generally felt that diphtheria and pertussis were serious infections for children, and that the need to protect beyond the childhood years was unnecessary. Subsequently, the booster given at 15 years and thereafter was the Td. Insofar as the antibodies waned with time, it was widely accepted that if an individual sustained a suspiciously dirty cut or puncture between the ages of 10 and 15 years the Td booster should be given at that time. Therefore, what is this new vaccine that is to be given at 11 or 12 years?
There has been a dramatic increase in the number of cases of whooping cough over the past few years. The incidence of pertussis in the United States reached an all-time low in 1976 with 1060 cases reported. In 2003 there were 11,647 cases reported, and in 2004 over 19,000. The mortality rate from pertussis was 10 per year in the 1990's, and has doubled since the year 2000. Why is this so?
Pertussis is a highly contagious respiratory tract infection that is caused by a bacterium, Bordatella pertussis. This infection is spread through direct contact with airborne droplets from an infected individual who merely coughs or sneezes. It can be a particularly devastating infection for infants and toddlers. Adolescents and adults can handle this infection much better than a child can. In the older patients it may present as a nagging and persistent cough, often times nothing more than a nuisance.
Since the old recommendation called for the final DPT to be given at five years of age, the protection against pertussis would naturally wane after that time period. A teenager or young adult would no longer be protected. From an epidemiological standpoint, that is exactly what was happening.
The incidence of pertussis in older patients increased dramatically. While it may have caused nothing more than a lingering nuisance cough for that individual it remained a highly contagious infection, and herein lies the problem. Young infants who had not been able to complete their initial series of vaccines were at risk for becoming infected. The older population served as a reservoir for pertussis. The young infants were becoming infected as a result, and many of them were becoming gravely ill.
To help stem the tide of this problem which was getting out of control, the Advisory Committee on Immunization Practices for the CDC met in Atlanta last year. They discussed a new licensed vaccine, Tdap, as a possible remedy for this problem. The Tdap vaccine is a tetanus booster that has a component of pertussis, which should help boost the immune response against pertussis and offer protection for adolescents. It is a very safe vaccine, and studies show that it is very effective in doing just that. Hence, by giving the tetanus booster at 11 or 12 years instead of 15, and offering a pertussis boost, the pool or reservoir of infected teenagers and young adults will diminish greatly. As a result, the overall number of pertussis cases should decrease significantly. This should be of great benefit to the "not yet protected" infants. A cost benefit analysis concluded that vaccinating individuals between 10 and 19 years of age with the Tdap in the United States over a 10 year period would prevent 1.8 million cases of pertussis. In addition it would save as much as 1.6 billion dollars in health care costs.
I explained all of this to Tommy's mother. She thought it was a great idea and was anxious to get her 13-year-old daughter in for her vaccination. Tommy, on the other hand, was not very impressed with the whole idea. To cheer him up I said, "Look on the bright side, Tommy; you won't have to get another tetanus booster until you are 21 years old!" He still was not impressed.