MedicalResearch.com Interview with:
Dr. Matthieu Domenech de Cellès PhD
Biostatistics, Biomathematics, Pharmacoepidemiology, and
Infectious Diseases Unit, Institut Pasteur, Inserm U1181,
University of Versailles St-Quentin-en-Yvelines,
MedicalResearch.com: What is the background for this study? What are the main findings?
Response: Most high-income countries now use acellular pertussis vaccines (called DTaP, which are sub-unit vaccines based on purified antigens of the bacterium Bordetella pertussis) to protect children against pertussis. Although clinical trials demonstrated the short-term effectiveness of DTaP vaccines, there was a growing concern that the duration of protection they conferred was not very long. Those concerns were mostly based on the results of a number of epidemiological studies, which showed that the relative risk of contracting pertussis increased substantially over time, typically by 20–40% every year since last vaccination.
Although such increases seem high, it was not immediately obvious how to interpret them—the more so because pertussis epidemiology is complex.
In our study, we developed mathematical models of pertussis epidemiology to try to understand what the results of recent epidemiological studies really meant about the effectiveness and the duration of protection of DTaP vaccines. The most interesting—and perhaps counterintuitive—finding of our study was that those results are fully consistent with highly effective DTaP vaccines, which confer long-term protection. This is a consequence of the fact that pertussis is highly contagious and that the immunity conferred by DTaP, though very high, is not perfect.
MedicalResearch.com: What should readers take away from your report?
Response: Our results add to the existing body of evidence showing that DTaP vaccines are effective and confer long-term protection. This should reassure physicians and their patients about the usefulness of DTaP vaccines, which have regularly been criticised.
MedicalResearch.com: What recommendations do you have for future research as a result of this work?
Response: An interesting open question is the duration of protection conferred by the acellular pertussis vaccines used in adolescents and adults, which are called Tdap and contain a dose of B. pertussis antigens lower than that of DTaP vaccines. Even though we found that the duration of DTaP immunity is long, it may be that Tdap vaccines confer shorter protection. This may have important implications for the control of pertussis.
MedicalResearch.com: Is there anything else you would like to add?
Response: Even though there remain many unknowns about pertussis, we hope that our study will lead to reconsider a number of widespread beliefs in the light of all available evidence. Disclosure: I received post-doctoral funding (through my former host unit at the Institut Pasteur) from Pfizer, for a project independent from this work.
Domenech de Cellès M, Rohani P, King AA. Duration of Immunity and Effectiveness of Diphtheria-Tetanus–Acellular Pertussis Vaccines in Children. JAMA Pediatr. Published online April 22, 2019. doi:10.1001/jamapediatrics.2019.0711
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