What’s behind the whooping cough epidemic?

Many people in the western Minnesota communities of Dawson and Boyd must have been surprised when pertussis, or whooping cough, broke out in 1998. I remember it well, especially for the concern it caused. By the time the outbreak was over, more than 30 people, mostly school-aged children, had gotten sick.

From the vantage point of nearly 14 years later, it seems to have been an early warning sign – in our own back yard, no less – of things to come.

An alarming increase in whooping cough cases in the United States has caught everyone’s attention this summer. For those in the public health field, however, there’s nothing new about it. Pertussis has been climbing in incidence for several years and it’s not completely clear why.

What we’re seeing with pertussis seems like a good illustration of how easy it can be to mistakenly assume we’ve eradicated most of the formerly common childhood diseases, such as whooping cough, and how challenging it is to maintain whatever progress has been made.

Many have been quick to blame the anti-vaccine movement for what’s happening. But although this is probably one of the contributing factors, it doesn’t seem to be the whole story.

The real issue could well lie with the vaccine itself. It’s now known that even among those who were vaccinated as children, the protective effects begin to wane by adolescence. Essentially this creates an enormous pool of teens and adults who may have become a reservoir for the pertussis bacteria and are unwittingly aiding in its spread, especially to infants and the very young who aren’t yet fully immunized. (Children need to be at least 2 months old to receive the vaccine, and it takes a series of shots to acquire full protection.)

Questions also have been raised about the vaccine formula. In the late 1990s the formula was changed from a whole-cell form of the pertussis bacteria to an acellular, or inactive form. Did this make it less effective? Did it somehow alter the control of the disease? On the other hand, evidence suggesting the vaccine lacks long-term effectiveness has been around longer than this, so a change in the formula might not adequately explain what’s happening. Although researchers have been exploring these issues for several years, the answers so far have been unclear.

Other research has found that the Bordetella pertussis bacterium may be evolving and perhaps is no longer well matched to the existing vaccine formula.

It was encouraging to hear this week that Affiliated Community Medical Centers here in Willmar has joined a project by the Minnesota Department of Health to increase the surveillance of whooping cough and collect more data. With more information, the public health community is in a better position to address the growing problem of whooping cough.

A couple of other points bear mentioning. First, although teens and adults do get sick from pertussis, their disease tends to be less severe – and as a result, it can go undiagnosed, allowing them to unknowingly spread it to others who might be much more vulnerable. The very young are usually hit the hardest; indeed, half of babies under the age of 1 year who develop pertussis end up being hospitalized.

Secondly, it’s critical for health providers to keep whooping cough on their radar screen. They may not see it often and they may assume that the vaccine has made it a non-issue. But as we’re learning, whooping cough is still very much present, and a persistent, hacking cough in an adult or severe cough in a child signals the need to look closer.

(For audio of what whooping cough sounds like, click here. Warning: Some may find it disturbing. Also, keep in mind that the characteristic high-pitched whoop at the end of the cough is not always present.)

Despite the tangle of issues surrounding the effectiveness of the whooping cough vaccine, it’s pretty clear that it’s still far better and safer to get vaccinated – and with the full series – than to skip it. Since we know that the vaccine wears off by adolescence, teens should get the recommended booster shot. Adults whose last pertussis vaccination was years ago and who’ve never had a booster shot should get one too, especially if they spend any time around young children.

It may not fully stem the tide, but there’s uniform agreement in the public health community that appropriate vaccination will go a long way toward closing some of the gaps in the immunity safety net and starting to bring down those alarming pertussis numbers.

2 thoughts on “What’s behind the whooping cough epidemic?

  1. Pingback: Adorable Cat Journalists, Silly Olympics Links and a Tornado Map | Oh Look, a Shiny Thing!

  2. Pingback: A Bit More on Pertussis | Oh Look, a Shiny Thing!

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