Acellular Pertussis vaccine less effective than whole-cell vaccine

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1. Teenagers vaccinated with acellular pertussis (DTaP) in infancy were at a greater risk of developing pertussis than those vaccinated with whole-cell pertussis (DTwP). 

2.  Each dose of DTap vaccine put children at higher risk for pertussis infection when compared to DTwP doses.  

Evidence Rating Level: 3 (Fair) 

Study Rundown: Although associated with a lower rate of adverse events than the original DTwP vaccine, multiple studies indicate waning immunity following DTaP administration. This study adds to previous research, showing a significant difference in pertussis protection among adolescents who received DTaP compared to DTwP in childhood.  This study also examined adolescents who received different combinations of the two types in their regular immunization course.  Those who received DTwP as a component of their first 4 vaccinations appeared to have increased protection with each additional DTwP vaccination. Due to the nature of the study design, children receiving more doses of DTwP were older than other participants. This limitation may be a confounding variable as pertussis incidence is strongly correlated with age. While, the clinical implications of this study are not known, researchers suggest working to develop a pertussis vaccine that is both safe and efficacious.

Click to read the study, published today in Pediatrics

Relevant Reading: California Pertussis Epidemic

Study Author, Dr. Klein, M.D. PhD talks to 2 Minute Medicine: Research Scientist II, Division of Research, Co-Director at Kaiser Permanente Vaccine Study Center, Kaiser Permanente Northern California and Adjunct Clinical Instructor, Department of Pediatrics, Lucile Salter Packard Children’s Hospital at Stanford 

“This study builds on earlier research into the waning effect of the acelluar pertussis vaccine, introduced during the 1990s to replace whole-cell pertussis vaccine. We looked at individuals born between 1994 and 1999 who received four pertussis-containing vaccines in the first two years of life. Some individuals received DTwP, and others received DTaP. During the 2010-2011 pertussis outbreak in California, we found that those teenagers who received DTaP had a six times higher risk of contracting pertussis due to waning immunity compared to those who received DTwP. Among teenagers who received DTaP, receipt of the TDaP booster did not overcome the advantage in protection from pertussis associated with previously receiving DTwP vaccines. Despite this, TDaP is still the best available means to help protect the DTaP-only group from pertussis. We conclude that that research into developing new pertussis vaccines with improved safety and long-lasting immunity is warranted.”                                                                        

In-Depth [case-control study]: This case-control study compared 138 pediatric PCR-confirmed pertussis cases to 899 PCR-negative cases and 54,339 matched controls. Participants were born between 1994 and 1999 and received their full infant pertussis vaccination schedule at Kaiser Permanante of Northern California. Children received either DTwP, DTaP, or a combination of the two for their first four doses and DTaP for their fifth. Those who received 5 TDaP doses had a nearly 6 times increased risk of having PCR-positive pertussis when compared to those who had DTwP for the first 4 vaccine doses (OR = 5.63, 95% CI: 2.55-12.46). Receiving a mix of DTaP and DTwP also increased the risk of having a PCR-positive pertussis (OR = 3.77, 95% CI: 1.57-9.07). More detailed analysis revelaed that each additional DTaP administration increased patients’ pertussis risk by 40% (OR = 1.40; 95% CI: 1.20-1.62, p < .001).

By Laurel Wickberg and Leah Carr

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