No Down Side to Booster Shot

Q:  I went to my doctor for an annual physical and she recommended a tetanus booster. While I'd rather not get a shot in the arm, I agreed to her recommendation, particularly because she told me that the new tetanus booster I got will protect me from whooping cough as well as infection with tetanus.

Now, I don't know anyone who has had either disease, and it makes me wonder, is it really worth it to get this shot? I am a healthy 34-year-old without medical problems.

A:  Immunizations prevent disease in humans by protecting the vaccinated individual (the patient who got the "shot") and by reducing the transmission of the disease so that it's less likely that anyone gets the disease. In other words, because you are immunized against whooping cough, you are partially protecting your family from this disease because you won't expose them to it.

Of course, someone else could expose them, but the more the population as a whole becomes immunized, the less likely anyone is exposed. (Smallpox did not die out because everyone got a smallpox shot, but because a critical mass of people did, and the disease could not spread.)

Whooping cough is an illness of coughing and chest congestion that can be confused with the common cold or bronchitis. It sometimes progresses to pneumonia.

You probably do know someone who had whooping cough (also called pertussis). The Centers for Disease Control and Prevention reported more than 11,000 cases in the United States per year since 2003, a number that has been increasing in the past 15 to 20 years and translates into about 0.5% of the population.

Since pertussis is significantly underreported, the true number of infected cases is probably much higher.

There are four combination vaccines used to prevent diphtheria, tetanus and pertussis: DTaP, Tdap, DT, and Td. Two of these (DTaP and DT) are given to children younger than 7 years of age, and two (Tdap and Td) are given to older children and adults.

Td is a tetanus-diphtheria vaccine given to adolescents and adults as a booster shot every 10 years, or after an exposure to tetanus under some circumstances. Tdap is similar to Td but also containing protection against pertussis. A single dose of Tdap is recommended for adolescents 11 or 12 years of age, or in place of one Td booster in older adolescents and adults age 19 through 64.

The vaccine prevents infection with pertussis about 90% of the time. Randy Lipchik, MD, a Professor of Pulmonary Medicine at the Medical College of Wisconsin, tells me that in the few vaccinated people who contract the infection, the disease is milder than in those who did not get the vaccine.

Finally, a word about tetanus: "It is unlikely that you would personally know someone who has had tetanus. Only about 70 cases per year occur in the United States," according to physician Andrew Petroll, MD, an infectious disease specialist at the Medical College of Wisconsin.

The low number of cases is precisely due to high vaccination rates.

But even though the risk is low, major health organizations, such as the Advisory Committee on Immunization Practice and the American College of Physicians, do recommend a tetanus booster every 10 years, as your doctor said.

That's because most people who get tetanus die from it, even with the best medical care.

Julie L. Mitchell, MD, MS, is an Associate Professor of Medicine at the Medical College of Wisconsin. She practices at the Froedtert & The Medical College of Wisconsin General Internal Medicine Clinic - East. Her column appears in the Milwaukee Journal-Sentinel.