Scientists at the U.S. Food and Drug Administration (FDA) vaccinated pregnant and infant baboons with acellular pertussis vaccine to study the effectiveness of maternal and neonatal immunization for the prevention of pertussis. The results demonstrated that infant baboons born of mothers that had been vaccinated during pregnancy were protected against pertussis when exposed to it five weeks after birth. The FDA study also showed that newborn baboons of mothers who had not been vaccinated were protected after vaccination at either two days of age or two and 28 days of age.
Pertussis, also known as whooping cough, is a contagious respiratory disease caused by Bordetella pertussis bacteria.Initial symptoms include runny nose, sneezing, and a mild cough, which may seem like a typical cold.Usually, the cough slowly becomes more severe.Eventually the patient may experience bouts of rapid, violent coughing followed by the “whooping” sound that gives the disease its common name, when trying to take a breath. The coughing fit may cause the patient to vomit or turn blue from lack of air.Pertussis can cause serious and sometimes life-threatening complications, especially in infants and young children, causing permanent disability, even death.
The results of the FDA study are important because the incidence and severity of pertussis is highest among infants too young to have completed the vaccination series. In addition, most hospitalizations and fatal cases of pertussis occur in infants less than three months of age.Moreover, the rates of infection in the U.S. have been rising over the last 30 years, despite vaccination of over 95% of children nationwide. The U.S. is now experiencing levels of pertussis comparable to those seen in the 1950s, with 48,000 cases reported in 2012.
Strategies to protect newborns from pertussis have been proposed. For example, “cocooning” which is vaccinating parents, family members and frequent contacts of newborns.However, ensuring all of the contacts are vaccinated is an approach that could be difficult to implement and the benefits of cocooning are unclear. Although previous studies have shown that vaccination during pregnancy and of newborns results in anti-pertussis antibodies in newborns, there is no confirmatory evidence that these antibodies are protective.
FDA scientists in the Office of Vaccines Research and Review (OVRR) have previously determined that the baboon closely reproduces the way pertussis disease affects people, and therefore is a relevant animal model to evaluate potential strategies to protect newborn infants from pertussis. In a previous study using the baboon model, the OVRR scientists found that while vaccination is effective in preventing pertussis disease, the animals still carry B. pertussis in their respiratory tract and can transmit the disease to unvaccinated baboons.
To evaluate the effectiveness of maternal vaccination for the prevention of pertussis, OVRR scientists vaccinated eight female baboons three times before pregnancy with an FDA-approved DTaP vaccine. Seven became pregnant and were subsequently administered a booster shot at the beginning of their third trimester of pregnancy. To evaluate the response in neonatal baboons, the scientists used an FDA-approved DTaP vaccine to immunize two infant baboons at two days of age and two baboons at both two and 28 days of age; three infant baboons remained unvaccinated.
When exposed to B. pertussis, all four vaccinated infant baboons produced high levels of antibodies and remained free of symptoms, even though their respiratory tract was highly colonized with the bacteria. The three unvaccinated animals developed symptoms of severe pertussis disease.
The seven infant baboons born to vaccinated mothers became heavily colonized by the bacteria after exposure to B. pertussis, but did not develop symptoms of pertussis.
FDA’s results in the baboon model provide a proof-of-concept in a primate model that maternal vaccination may confer protection against severe pertussis during the first months of life.
“Maternal and Neonatal Vaccination Protects Baboons from Pertussis Infection”
Journal of Infectious Diseases
2014; doi: 10.1093/infdis/jiu090
Jason M. Warfel(1), James F. Papin(2), Roman F. Wolf(2), Lindsey I. Zimmerman(1) and Tod J. Merkel(1)
(1)Division of Bacterial, Parasitic and Allergenic Products, Center for Biologics Evaluation and Research, FDA, Bethesda, Maryland, USA
(2)Oklahoma Baboon Research Resource, Comparative Medicine, University of Oklahoma Health Sciences Center, Oklahoma City, Oklahoma, USA