Surprising Whooping Cough Outbreak in Florida

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Pertussis Outbreak, FLAIn September 2013, local county health officials in Tallahassee, Fla. were notified of a laboratory-confirmed case of pertussis, or whooping cough, in a 1-year-old preschool attendee. The preschool enrolled 117 students, aged six months through six years. During the subsequent five-month period, 26 students 1 5 years of age, two staff from the same preschool, and 11 family members met the national case definition for pertussis.

Four persons during this outbreak were hospitalized for clinical management of pertussis symptoms. Only five students, including two students with pertussis, had not received the complete series of vaccinations. Adding to the evidence that inadequate or skipped vaccinations were not the cause of this outbreak, attack rates in one classroom in which all students had received the complete series of vaccinations for pertussis approached 50 percent.

The report of the outbreak appeared in the journal Emerging Infectious Diseases, and was written by James Matthias, MPH, of the Florida Dept. of Health, with contributions from the CDC as well. It is entitled "Sustained Transmission of Pertussis in Vaccinated, 1 5-Year-Old Children in a Preschool, Florida, USA."

This outbreak raises concerns about vaccine effectiveness in this preschool age group. In the United States, incidence of pertussis is greatest among infants, children 7 10 years of age, and adolescents. During 2000 2012, reported pertussis cases increased greater than six-fold, from 7,867 cases to 48,277 cases.

One potential contributing factor for increased incidence of pertussis is waning immunity after acellular pertussis vaccination. As we ve reported before, studies suggest that the newer tetanus, diphtheria and pertussis vaccine TDaP acellular vaccine, that contains only certain components of the Bordetella pertussis bacteria is at least partially to blame for recent increases in pertussis outbreaks. While the acellular vaccines result in fewer adverse effects compared to the older whole-cell vaccines, they are less protective. Acellular pertussis vaccines replaced whole-cell vaccines for the five-dose childhood vaccination series in 1997.

In 2012, Washington State had an outbreak of pertussis. Nearly 5,000 people mostly babies and children caught the disease. Surprisingly, many of the affected adolescents had been vaccinated on schedule, according to a study in Pediatrics. That analysis reported that the effectiveness of the acellular pertussis booster shot (TDaP) dropped dramatically within a few years, leaving children and teens vulnerable.

The authors point out that these results reinforce the idea that recent pertussis vaccination should not dissuade physicians from diagnosing, testing, or treating persons with compatible illness for pertussis and taking appropriate action to prevent wider transmission. While pertussis is quite annoying for weeks in older patients, it can be very severe in infants and toddlers, and has caused deaths.

We really need to keep in mind that while vaccines are not perfect, they are still the best way to provide protection among children and adolescents. The acellular vaccine efficacy wanes quicker than we d like, that does not mean it s OK to skip it quite the contrary in fact.

Those who fail to get their kids vaccinated on schedule are contributing to the recrudescence, or revival, of epidemics. We don t know the solution for this particular problem, aside from more research aimed at providing a better vaccine. Until then, teens and adults should be encouraged to get a booster pertussis shot, especially if they are going to be in the company of infants with little protection. New mothers would be well-advised to make sure friends and relatives who visit are up-to-date with their vaccinations, including pertussis boosters.