Pertussis is more likely in infants who are born prematurely, compared with infants carried to term, according to Dr. Øystein Rolandsen Riise of the Norwegian Institute of Public Health, Oslo, and associates.
Using data from the Medical Birth Registry of Norway, 713,166 children were monitored until the age of 2 years from 1998 to 2010, during which time 968 cases of pertussis were laboratory confirmed. The incidence rate in term infants was 67.9 cases per 100,000 person-years, and was 115.2 cases per 100,000 person-years for preterm infants. The overall incidence rate ratio (IRR) of pertussis for preterm infants was 1.65, compared with term infants.
Hospitalization due to pertussis also was significantly more likely in preterm infants, with an overall IRR of 1.99, and infants born at 23-27 weeks again faced a greatly increased risk, with an IRR of 5.28.
Three-dose vaccine effectiveness against reported pertussis was 88.8% in term infants and 93% in preterm infants.
“Early and timely pediatric vaccinations as well as other strategies to prevent transmission to preterm infants are of utmost importance,” the investigators wrote.
Find the full study in the Pediatric Infectious Disease Journal ().