Marin Voice: Older, vaccinated children are still susceptible to pertussis

Many teenagers around Marin County are coughing and breathless right now.  Pertussis is back in a big way.

You might have thought this disease, often called whooping cough, has been eradicated given we have immunizations available to prevent it.  However, we are now seeing an outbreak of this disease among teens even though the immunizations are doing exactly what they are supposed to do.

Whooping cough is the severe and life-threatening disease seen in infants and young children that is caused by the Bordetella pertussis bacteria. The disease has a characteristic cough and causes respiratory distress. At the turn of the 20th century, tens of thousands of children every year died from the cough. In the 1930s, researchers in the Michigan Department of Health developed the whole-cell pertussis vaccine. Its rapid adoption led to an end to nearly all deaths from whooping cough in infants and young children.

Pertussis cough illness is what teenagers and adults get from the pertussis infection.  This is a severe, frequent cough that lasts for 100 days and is not treatable with any prescription or over-the-counter cough or asthma remedy.  Insomnia, chest pain, and loss of activities go on for the full three months.  However, teenagers and adults with this ailment are rarely even hospitalized.

What we are seeing in Marin County right now is pertussis cough illness. As of last week, there were more than 70 cases at Tamalpais High School and lots of other clusters among teenagers in the county.

So why are we seeing pertussis among teenagers right now? This goes back to the vaccination. In the 1970s and ’80s, concerns about potential rare, but serious side effects, like brain damage, led to the whole-cell pertussis vaccine becoming untenable. In the early 1990s, the United States adopted a newer vaccine for pertussis, called the acellular vaccine, as a booster to the whole cell series.  The acellular vaccine had fewer side effects.  Within a couple years, this vaccine was used for all pediatric pertussis immunizations.

In 2010, there was a big and unexpected outbreak of pertussis among children in Marin County.  We figured out the newer vaccine does not last as long as the previous one.  While there is excellent protection for a year after the last booster, the immunity to pertussis infection decreases by about a third every year thereafter. Because the last vaccine in the series is given between 10 and 12 years old, by age 14 or 15 protection has waned. This means high school students are susceptible to pertussis cough illness, while younger children who have had the primary series, remain well protected.

The vaccine, which was developed to prevent the death of infants and young children, is doing its job.  But pertussis cough illness in teens remains a problem.

The good news is that since the 2010 outbreak, research teams have been making progress in developing a more durable pertussis vaccine.  This should solve the problem of pertussis cough illness in teens and adults, but it will likely take several more years until it’s available.

Pertussis is effectively treated by an antibiotic called azithromycin taken by mouth for 5 days.  Any household contact or close contact also should be treated with azithromycin as a prevention.  Any close contact with the cough should also be tested for pertussis with a swab deep in their nose. Anyone with pertussis also needs to isolate at home for the full 5 days of treatment.

Although this present outbreak is disrupting many people’s lives, thanks to the vaccine we are not seeing hospitalizations or deaths.  Early treatment for pertussis will help slow and stop this outbreak.

Dr. Paul Katz is a pediatrician at Kaiser Permanente San Rafael.