FROM EMERGING INFECTIOUS DISEASES

Preschool-age children who have been fully vaccinated against pertussis can still develop symptoms of illness consistent with a whooping cough diagnosis, according to a study of toddlers in a Tallahassee, Fla., school that experienced an outbreak of pertussis in late 2013 (Emerg Infect Dis. 2016 Feb;22[2]. doi: 10.3201/eid2202.150325 )

The study, published in Emerging Infectious Diseases by the Centers for Disease Control and Prevention, is the result of an outbreak investigation at the preschool that began after a 1-year-old and two 3-year-old children developed illness consistent with pertussis, and were confirmed to have pertussis after undergoing a polymerase chain reaction (PCR) test.

The Florida Department of Health administered a questionnaire to be completed by families of the 117 students (ages 10 months to 6 years) and 26 staff members. Questionnaire completion rate was 98%, with three student households and one staff household failing to complete it.

Overall, 28 cases were determined to be “probable” pertussis and 11 were confirmed as pertussis via PCR or other laboratory testing methods. Of these, 26 were students aged 1-5 years (22% of total student population), 2 were attributed to the staff (7%), and 11 were linked to the preschool, of which 9 originated from the households of the individual students and 2 from “camp counselors who had contact with a sibling of a laboratory-confirmed case-patient who attended the preschool.”

However, 28 of the students who had pertussis had received at least three vaccinations, with 23 of them having received at least four vaccinations, meaning they were classified as being fully vaccinated against the disease. Only 5 out of the school’s 117 children had not received the complete series of vaccinations, out of which 2 ended up being case-patients; both of those children, however, had received at least one vaccination prior to falling sick.

“Poor performance of a vaccine in a defined cohort might suggest a provider-level failure to store, use, and administer the vaccine properly,” noted the researchers, led by Dr. James Matthias of the Florida Department of Health. “Although we did not assess vaccine storage and handling practices, children from this investigation were seen by multiple providers in the community [and] no general increase in reported pertussis incidence was observed in the county at the same time as this outbreak.”

The bottom line, the authors concluded, is for pediatricians and primary care doctors to be wary that vaccination against pertussis doesn’t necessarily mean patients can’t ever get it. If pertussis symptoms arise in a vaccinated child, especially one 5 years old or younger, it may still be whooping cough.

The CDC supported the study. Dr. Matthias and his coauthors are all affiliated with the Florida Department of Health and the CDC, but reported no other relevant financial disclosures.

dchitnis@frontlinemedcom.com

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