Pertussis is making a comeback – what’s the best protection?

The Pediatric Insider

© 2019 Roy Benaroch, MD

Pertussis is also known as “whooping cough”, or sometimes “the 100 day cough”, or sometimes “DAMMIT WHY CAN’T I STOP COUGHING?!”. It is truly miserable. In adults and teens, three months of coughing – and I mean serious, loud, hard coughing, sometimes until you break a rib, vomit, or pass out – is not fun. Young babies, instead of coughing their little heads off, sometimes just stop breathing.

Unfortunately, it’s making a comeback. Both national statistics and our experience at my offices are showing increasing numbers of pertussis cases. Pertussis had become very uncommon with widespread vaccination by the 1980s. Why is it back?

(Aside: about 25 years ago, in my very first month of training as a pediatrician, I was taking care of a newborn in the emergency department who stopped breathing. Completely. Just stopped. Turned blue and floppy. I was terrified, but kept my cool and performed mouth-to-mouth resuscitation. The baby did fine. Later, my attending told me to never use my mouth on a baby – there was resuscitation equipment literally hanging on the wall behind me that I didn’t think to use. Oops. Later, I found out the baby had pertussis.)

The first pertussis vaccine was developed in the 1930s, and in the 1940s it was combined with tetanus and diphtheria vaccines to create the “DTP” vaccine. This was very effective at preventing pertussis, but it was quite “reactogenic”. DTP commonly causing fevers and sometimes febrile seizures (which, by themselves, are harmless – but really scary.) There were cases of encephalitis and dramatic developmental regression seen, too, though it’s become clear since then that these were cases of the genetic condition Dravet Syndrome, which unfortunately starts showing symptoms around the time DTP was given. The quest was on for a pertussis vaccine that caused fewer fevers, and a newer, more purified “acellular” DTaP was developed.

After extensive studies showed that the DTaP was effective and caused fewer fevers, the acellular vaccine replaced the older, “whole cell” vaccine in the US and many other developed countries in the 1990s. And, at least at first, things seemed to go well. Pertussis cases remained low.

But we’ve seen a steady increase in cases over the last 10-15 years. Part of that could be ascertainment bias – there are newer, better, and faster tests for pertussis that have come into wider use, and doctors think about testing more kids for pertussis now that’s clear there are more cases. That doesn’t explain all of the increase.

A study published this week in Pediatrics has helped clarify what’s going on. About a half million children managed at the huge Kaiser Permanente system in Northern California were studied, looking at their pertussis vaccine status and the rates of proven cases of pertussis in the group. Almost 750 cases of pertussis were documented in these children from 2006-2017, revealing some important conclusions:

  • Pertussis risk, overall, was 13 times higher in unvaccinated versus fully-vaccinated children. The vaccine is protective.
  • Still, 80% of the cases occurred in children who had received the full set of doses. Pertussis immunity dropped off over time – and the longer since the most-recent dose, the more at-risk a vaccinated child became.

So what should we do?

First: widespread, continued universal DTaP vaccinations in infancy and Tdap boosters for preadolescents is still a good idea. It is far better than not vaccinating. The Kaiser data clearly shows vaccinated individuals are at lower risk. Since one of the highest risk groups for severe disease is newborns, vaccinating pregnant women is a key strategy. Though maternal pertussis immunity after Tdap doesn’t last long, it does last long enough to transfer protective antibody to the unborn baby, providing crucial protection during the first few months of life.

But we clearly need a better vaccine and other strategies to provide better, more-lasting protection. Alternatives are being studied, including a nasal-spray pertussis booster and new, adjuvanted vaccines that can hopefully provide more-lasting protection safely. New vaccines take many years to study, so don’t expect anything on the market soon.

In the meantime, we need to do the best we can. Make sure you and your children are fully vaccinated against pertussis, and follow the recommendations for all vaccines. We need to be a better job developing better tools, but in the meantime we could be doing a better job using the tools we’ve already got.

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