Adults should get booster to ward off whooping cough

Dear Doctor K: My daughter wants me to get a booster shot for pertussis. She says it will help protect her young kids against whooping cough. Is this true?

Answer: Your daughter is right. Pertussis, also known as whooping cough, is a highly contagious bacterial infection that causes violent coughing. The coughing makes it hard to breathe and produces a deep “whooping” sound. Pertussis can occur at any age, but infants and young children are most likely to become seriously ill from the infection.

When I went to medical school, a vaccine for pertussis was radically reducing the number of cases. It was another example of how infectious diseases were going away because of vaccines. The vaccine has, indeed, made a huge difference. But vaccines work only if people take them, and not every vaccine offers lifetime protection.

Unfortunately, many people resist getting vaccines, and the protective effects of the pertussis vaccine tend to decline over time. As a result, the number of pertussis cases in the United States has increased in recent years. There were about 17,000 reported cases in 2009; this year, more than 23,000 cases of pertussis had already been reported by August.

To keep kids healthy, adults need to get immunized, too. That’s because of something called “herd immunity.” When enough people are immunized against a disease, it becomes uncommon — simply because the immunized people can’t catch it — and therefore can’t spread it.

Herd immunity helps to protect the following:

Small children, especially infants, who either are too young to be immunized or haven’t had enough doses to be fully protected.

People who have problems with their immune systems, many of whom can’t get vaccines, and all of whom are more susceptible to infections.

Herd immunity works when enough people are immunized. The Centers for Disease Control and Prevention (CDC) recommends that adults get a Tdap vaccine (which protects against pertussis, along with tetanus and diphtheria) in place of one of their regular tetanus boosters (the Td shot that is recommended for adults every 10 years).

You can get the Tdap vaccine no matter when you last received a Td shot. Getting vaccinated with Tdap at least two weeks before coming into close contact with an infant is especially important.

By getting a Tdap vaccine, you’ll be helping to keep your grandkids healthy. Even though that’s the main message of this column, it is worth remembering that we adults also need protection against the germs spread by little kids.

Several months ago, a family with young children visited us, and one of the kids had what we in New England call a “wicked cough.” About two weeks later, I developed a bad cough, and when I took in a deep breath I let out a loud “whoop!” Like everyone, I’ve had plenty of coughing illnesses in my life. But I’ve never (not even as a kid) “whooped.”

I got better, but I wonder if I caught pertussis from our young visitor. Fortunately, I stopped coughing the next day, and so I never tested myself and never will know if I had it.