According to a report released today in the journal Emerging Infectious Diseases, over a five-month period starting in late 2013, more than two dozen children in a Florida preschool were diagnosed with pertussis (also known as whooping cough). In addition, two members of the staff and 11 family members or other contacts of children there also met criteria for diagnosis.
Nearly all the children in the preschool had been completely vaccinated against the illness.
To say that I am unenthusiastic about reporting this outbreak would be something of an understatement. I am an unambiguous proponent of comprehensive vaccination for all children, except those with a medical condition that precludes it. However, responsible medical providers and public health officials have a duty to accurately inform people when something goes wrong. (Hint: if there really were a massive Big Pharma conspiracy to poison kids with shots, we’d probably make more of an effort to cover this sort of thing up.)
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The investigation into the outbreak began in December of 2013, when a 1-month-old infant tested positive for the disease. It was determined that an older sibling (who had been vaccinated) and the infant’s mother both had had symptoms consistent with the illness prior to the baby’s diagnosis. Following a query from the county’s Department of Health, the preschool began a surveillance program and reported any new cases of an illness involving a cough.
A total of 26 students at the school were eventually identified as having pertussis. Of the more than 100 children in the preschool, only five had not been fully vaccinated. The two classrooms that had the highest attack rate (AR) from the disease were populated with 3-year-olds; one had an AR of nearly 50 percent as well as an infectious staff member.
For advocates of vaccination, it would be comforting if we could pin this outbreak on improper storage or administration of the pertussis vaccine. That seems unlikely, however. The report notes that affected children had received their immunizations from various providers in the community, and there was no increased incidence of disease within the county as a whole. It seems the vaccine simply was not as effective as it should have been.
This may stem from a change in the kind of vaccination used to protect against whooping cough, made decades ago. Earlier versions of the DTP vaccine (which also protects quite well against diphtheria and tetanus) were produced using broken-down whole cells of pertussis bacteria. While effective, safety concerns about rare but serious reactions to the whole-cell vaccine began to emerge. This led the development and licensure in the early 1990s of the DTaP vaccine currently in use, an “acellular” version that does not contain the older component and causes less of a reaction (PDF).
Unfortunately, it may not confer as much protection, either. This is due, at least in part, to there being only five immunity-triggering elements to the vaccine, instead of the thousands found in the whole pertussis cell.
“DTaP has long been known to have waning immunity,” explained Dr. Saul Hymes, a pediatric infectious disease specialist at Stony Brook University Hospital, in response to my questions about the new report. “But what this usually means is that, other than those who are unvaccinated, the vaccinated children who would be at greatest risk are those ages 7-10 or teenagers. These are the age ranges with the greatest gap between vaccines; this outbreak is very strange in that nearly all the cases were in infants and children who were appropriately vaccinated for age.”
Dr. Hymes has a couple of theories as to what could have contributed to the Florida outbreak.
“The close proximity and high ease of transmission in a daycare setting meant extremely high bacterial loads were being passed around that could have overcome any waning immunity present,” he continued. “I think pertussis outbreaks are in general under-recognized. It isn’t tested for or clinically identified nearly as often as it should be. It may be the case that our estimates of real-world vaccine efficacy may be overly optimistic if there is actually more pertussis that isn’t being diagnosed.”
This is certainly consistent with an additional finding discussed in the article. Even though there was a confirmed outbreak in their area, many physicians were reluctant to test for or diagnose pertussis because their patients had been recently vaccinated. The authors admonish providers to consider pertussis, even in vaccinated patients, when there is reason to be clinically suspicious.
It bears mentioning that, despite failing to prevent this outbreak, there were still benefits to vaccination against pertussis. In many cases the illness was difficult to recognize because whooping cough is often much milder in patients who have been immunized. And while far below optimal levels, the study did report about 45 percent efficacy in preventing the disease, too. As Dr. Hymes noted in our communications, 45 percent is a lot better than zero.
“Despite the outbreak, [this article] still shows how good vaccines are,” he went on. “Very few [a total of four] of the patients who got pertussis wound up in the hospital and none died. The outcome would have almost certainly been worse with unvaccinated children.”
But I could bankrupt myself at Sephora and still not turn this pig into a prom queen. The news from Florida is not going to make things any easier for those of us who advocate for the benefits of vaccinating your kids. Vaccinations remain a hugely contentious issue for many, much to my dismay.
For evidence, one need look no farther than the huge response that ensued when Facebook founder Mark Zuckerberg posted a status update of his kid at the doctor’s office with the caption “time for vaccines!” (Thank you, Mark. I hereby forgive you for all those “memories” Facebook keeps insisting I should be sharing.)
But whatever vaccine opponents make of this news, it doesn’t form a basis for any kind of solid argument against administering them. It provides evidence that vaccines against one particular illness aren’t as effective as they should be, and that work on a more effective version is necessary. It reminds providers that pertussis should still be on their minds if they see a patient with a prolonged cough, even if that patient has been vaccinated. And it demonstrates that even a suboptimal vaccine is still better than none.
What it doesn’t say is anything about the other safe, effective vaccines against other diseases. It doesn’t even mean it’s not worth it to vaccinate your kids with the DTaP vaccine that’s currently available. Better to get a milder form of an otherwise potentially fatal illness, after all.
It may not be news happy to report, but it doesn’t change anything about what I’ll be recommending to my patients.
