WHOOPING COUGH: “A DISEASE TO AVOID LIKE THE PLAGUE”

Pertussis or whooping cough (named for the characteristic though occasionally absent “whoop” at the end of a coughing episode) is a potentially serious disease at all ages but particularly in very young infants. It starts  out deceptively resembling a cold, with a runny or stuffy nose, sneezing, and a mild cough. Over the next week or two, the cough becomes increasingly severe, with violent repeated coughing, gasping for breath after a coughing fit, difficulty eating and drinking, sometimes progressing to dehydration and exhaustion as well as pneumonia. About half the babies afflicted with pertussis will spend time in the hospital. Some will die.

From 1926-30, more than 36,000 deaths from pertussis were recorded in the US. Then, in the early 1940s, an effective vaccine was developed. Although its side effect profile was not completely benign (mostly mild but in rare cases, seizures), it was a relatively safe procedure compared to the risks of pertussis and by 1948 had led to a dramatic decrease in whooping cough cases and deaths. Indeed, some even dared to hope the disease could be eradicated. (So far, even to this day, only one human disease, smallpox, has been completely eradicated, along with a handful of diseases that were once the scourge of livestock.) 

In the 1970s, just as the disease was reaching a historically low ebb, controversies about the safety of the Diphtheria-Pertussis-Tetanus (DPT) immunization erupted around the world. Documentaries and newspaper reports purporting to demonstrate neurological damage alarmed the public, followed by an even more inflammatory 1982 film entitled Vaccination Roulette, which claimed the immunization could cause permanent brain damage. Victim advocacy groups sprang up, lawsuits against manufacturers were filed, vaccine prices rose, and some companies even discontinued manufacturing the vaccine. Research confirming the safety of the DPT immunization and a strong counter-response especially in the US somewhat calmed but could not fully quell the furor. Immunization rates went down.

Sound familiar? This predated the media storm provoked by the fraudulent research of Dr. Andrew Wakefield demonizing the Measles-Mumps-Rubella immunization and its supposed connection with autism, and perhaps even provided a template for that campaign.

For better and for worse, these concerns led to the development of a new pertussis vaccine, introduced in 1998, which causes fewer side effects and is better tolerated but also wears off more quickly and may be less effective.

Pertussis, once thought to be consigned to the junk heap of history, has now come roaring back, with a measurable increase in baseline levels of the disease and epidemics every few years during which morbidity and mortality spike. It is far more common that other vaccine-preventable diseases such as measles and rubella. The reasons for this resurgence have yet to be fully explained. In part it may simply be an artefact of improved surveillance in adults - in whom, make no mistake, pertussis can also lead to serious illness. Genetic changes in the bacterium and the reformulation of the vaccine may also have contributed. There can be little doubt that reduced uptake of the vaccine, further fueled by the more general suspicion of vaccination that now prevails in the US, is also a factor. Numerous studies have demonstrated a negative correlation of pertussis vaccination rates with both morbidity and mortality. 

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​The biggest chink in our armor has always been the youngest sector of the population, infants who have not yet started or have only partly completed the immunization process. They are at once the most vulnerable to serious complications and the least protected from exposure. As Dr. Benjamin Spock warned in 1946 - in stark contrast to his generally reassuring tone - pertussis is “a disease to avoid like the plague if you have a baby in the household.” Those words remain as true today as when first he uttered them. The vast majority of pertussis deaths occur in infants aged 3 months and under.

The immunization sequence starts at age 2 months; after a series of boosters, the child is considered fully immunized at age 15-18 months when the fourth shot is administered. Until then, babies and especially newborns are desperately in need of societal protection.

​How best to provide that protection, however, is a topic that continues to evolve. Initially the Center for Disease Control’s recommendations focused on “cocooning,” encircling each newborn with an impenetrable shield by avoiding exposure to anyone who might possibly have the disease. Among people with pertussis, even those who may not know they have it, the attack rates among “susceptible household contacts” (that is to say, mostly babies) are as high as 80%, so the goal was to ensure that parents, siblings, and caregivers were vaccinated. Beyond that, or failing that, babies were dependent on herd immunity - that is, minimizing the spread of the disease by maintaining a vaccination rate high enough to reduce the likelihood of exposure to an active case. The percentage of vaccinated individuals needed to provide herd immunity varies from disease to disease but for pertussis is well above 90%.

Because this approach did not produce fully satisfactory results, the CDC in 2013 modified and expanded its strategy: Instead of focusing solely on cocooning, it first and foremost emphasized vaccination of all pregnant women irrespective of previous history of vaccination, ideally in the last trimester of every pregnancy, in order to confer passive immunity on the infant until s/he is old enough to be vaccinated. 

And that’s where we now stand in the year 2017. (Check out the CDC's FAQ on pertussis for a good summary of the issues.) Despite the shortcomings of the current vaccine - it is only around 85% effective and confers immunity for only a few years - no trials of improved vaccines are currently underway.

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In February of 2005, in anticipation of attending a conference in Eastern Europe, I visited the University of Michigan’s Travel Clinic to make sure my immunizations were up to date and received a routine “tetanus shot.” When I received my paperwork at check-out, I noticed my shot had been recorded as “Tetanus, Diphtheria (age 7-adult) (Td P-Free).” Huh? I’d always thought of the tetanus shot as “DPT.” When I inquired what had happened to the P, I was assured that what I had received was in compliance with CDC recommendations for people over 65. Never mind that I was still three years short of 65; close enough, they said.

Then in 2010, a whooping cough epidemic in California made national news, with the highest number of cases reported since 1955, and I once again wondered - not just whether I was adequately protected, but also whether there was any danger of exposing my grandchildren to this disease. I decided I would put the P back in DPT and at my next visit in January 2011 requested the current equivalent recommended for people age 11-64, even though I had now reached the age of 65. 

Turns out I wasn’t the only one to notice. In October of 2010, the Advisory Committee on Immunization Practices (ACIP) issued a new recommendation that anyone older than 65 be vaccinated for pertussis, though only if s/he had not received a prior dose of Tdap and if s/he expected to have close contact with an infant under one year old. A few months after I made my request, one of the two widely available pertussis vaccines for adults was approved for use in individuals over the age of 65, so an off-label use of the drug was no longer required. Since grandparents have been shown to account for 6-8% of newborn exposure to pertussis, babies were seen as the main beneficiaries of this change, but it also confers an extra measure of protection in seniors whose immune systems might not be working as well as they once did.

Still, since immunity wears off after a few years, I couldn’t help wondering why repeat doses still leave out the P. The answer took a little googling but the rationale seems to be twofold: 1) the CDC is investing its efforts in vaccinating pregnant women as its main strategy for protecting infants; and 2) the vaccine has not yet been adequately tested in people over 65. Pharmaceutical companies are apparently compiling data to respond to the second issue as we speak, so watch for a possible change in this policy as well.

Even though I don’t currently have a newborn grandchild, I for one am happy to be part of the effort to protect any infant with whom I might come in contact and to contribute to the overall level of herd immunity. I’ve always been a belt-and-suspenders sort of person, so vaccinating pregnant women combined with maintaining high levels of immunity in the general population makes a lot of sense to me.

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A parting shot for any pregnant woman or mother of a newborn baby: If for whatever reason you've elected not to have yourself or your other children vaccinated - be it mistrust of the government or mistrust of the pharmaceutical industry or religious scruples - or if you haven’t bothered because you’ve never seen a case of whooping cough or think herd immunity will protect your baby, or if you’ve just been too busy to complete your children’s vaccination program, please take a moment to LISTEN TO THESE HEARTBREAKING NARRATIVES shared by women whose lives have been forever changed by pertussis.

​Losing a child is devastating. Losing a child after knowingly rejecting or neglecting measures that could have prevented that death is beyond devastating. It will haunt you for the rest of your life. Don’t be that mom.