December 18, 2018
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Young infants at risk for severe pertussis despite acellular vaccine programs

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Photo of Manish Sadarangani
Manish Sadarangani

Infants aged younger than 2 months had higher rates of morbidity and death related to pertussis in the era of acellular vaccination, according to a study published in the Journal of the Pediatric Infectious Diseases Society.

“There is still a significant burden of severe pertussis disease in Canada, despite the success of current vaccines,” Manish Sadarangani, MA, BM, BCh, MRCPCH, DPhil, an assistant professor of pediatric infectious diseases at the University of British Columbia and director of the Vaccine Evaluation Center, BC Children’s Hospital Research Institute, told Infectious Diseases in Children. “The youngest and most vulnerable children (including premature babies) in our population are at highest risk for the most severe outcomes.”

Recent research found that the overall incidence of pertussis in the United States increased between 2000 and 2016, with age-specific case counts coinciding with the transition to acellular vaccination. In that study, researchers wrote that despite substantial declines in disease since the vaccine was introduced, pertussis incidence increased in several countries in recent years.

Sadarangani and colleagues noted that having data on pediatric pertussis using data from a large population over time would help to establish “the true burden of disease for the [acellular pertussis] vaccine era.”

They studied 1,402 patients aged 16 years and younger with pertussis who were admitted to 12 pediatric tertiary care hospitals in Canada between 1999 and 2015.

The researchers reported that younger infants — those aged younger than 2 months — experienced the highest mean annual incidences of pertussis hospitalization (116.4 per 100,000 population; 95% CI, 85.32-147.49) and ICU admission (33.48 per 100,000 population; 95% CI, 26.35-40.62). There were 25.46% of children requiring ICU admission, with infants aged younger than 2 months experiencing the highest proportion of ICU admission, at 37.9%.

Sadarangani and colleagues wrote that 21 deaths occurred between 1999 and 2015. Independent risk factors for ICU admission included age younger than 16 weeks, prematurity, encephalopathy and a confirmed diagnosis of pertussis. Independent risk factors for death included age younger than 4 weeks, prematurity and female sex.

“Pertussis vaccination in pregnancy is now recommended for all pregnant women in Canada in every pregnancy and is the most effective means we have to protect these youngest babies — it is now imperative that these immunization programs are implemented across the country,” Sadarangani said. “While we know that pertussis immunization in pregnancy is safe and effective, there are still remaining research questions to confirm the best time to vaccinate during pregnancy and increase our understanding of immunology of immunization in pregnancy.” – by Bruce Thiel

Disclosures: Sadarangani reports being an investigator on research grants received from Pfizer, Merck and Variation Biotechnologies, with all funds paid to his institution and not having received any personal payments. Please see the study for all other authors’ relevant financial disclosures.