A child who has never been vaccinated against pertussis, or whooping cough, is 13 times more likely to suffer from an infection of Bordetella pertussis than is a child who is up-to-date on his or her vaccines.

But new evidence from a decade-long study at Kaiser Permanente shows that vaccinated children were five times more likely to suffer from whooping cough if it had been more than 3 years since their last vaccine dose. The research was published today in Pediatrics.

DTaP vaccine, which protects against pertussis, diphtheria, and tetanus, is given in five doses between the ages of 2 months and 6 years. In this study, researchers from Kaiser Permanente Northern California followed children born between 1999 and 2016 who were diagnosed as having whooping cough.

The researchers identified 738 pertussis cases, with 99 cases in unvaccinated children, 36 in undervaccinated children, 515 in fully vaccinated children (five DTaP doses), and 88 in children who had received six doses of DTaP.

More than 80% of cases occurred in fully vaccinated children. Children only partially vaccinated were 1.9 times more likely to contract whooping cough than fully vaccinated peers.

“Although noncompliance with the vaccination schedule is an important public health problem that leads to increased pertussis risk, most children in our study received all their recommended DTaP doses,” the authors wrote. “Our results reveal that waning of DTaP immunity was an important cause of pertussis in children.”

In 2010 and 2014, California experienced two large pertussis outbreaks, with more than 9,000 cases each.

CDC [Public domain], via Wikimedia Commons

Read more at CIDRAP…

See also:

Jun 10 Pediatrics study

Jun 10 Pediatrics commentary