Although there is an effective vaccine against Bordetella pertussis, whooping cough remains a leading cause of death. Cases are increasing, and scientists face challenges in developing new vaccines.
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In a key research session at the start of the annual meeting of the European Society for Paediatric Infectious Diseases, held virtually this year, Dimitri Diavatopoulos, PhD, associate professor at the Radboud University Medical Centre Nijmegen, the Netherlands, summarized the pertussis vaccination problem and what the Pertussis Correlates of Protection Europe (PERISCOPE) project seeks to achieve. Dr. Diavatopoulos has a longstanding interest in pertussis and immunity and will soon take over as the scientific coordinator of PERISCOPE.
Pertussis is a highly contagious infectious disease that causes uncontrollable coughing. The disease begins with an atypical cough and rhinorrhea before entering a paroxysmal stage characterized by cyanosis, lymphocytosis, vomiting, and whoops. Generally, fever is absent and coughing increases at night. Finally, after weeks to months, the patient enters a convalescent stage. The World Health Organization estimates that there are 16 million pertussis cases annually and approximately 195,000 deaths in children. Most cases are caused by Bordetella pertussis and are preventable by vaccination.
In the United States, following the introduction of a national immunization program using a whole-cell vaccine in the 1950s, cases fell significantly. After a lag phase, the adoption of an acellular vaccine in the United States in 1997 and the Netherlands in 2005 – usually in combination with diphtheria and tetanus via DTaP – saw an increase in case numbers. Dr. Diavatopoulos stated that control is no longer as good, compared with other infectious diseases prevented by the MMR vaccine, such as mumps, measles, and rubella.
In the face of increasing numbers, how do we move to the next generation of vaccines to improve control? There are several barriers to licensure, including the following:
• Universal recommendation for pertussis prevention means that more than 90% of the population will have received DTaP (usually in combination with polio and Haemophilus influenzae B) and be protected for several years after vaccination.
• Because DTaP vaccines are only efficacious for a limited time, the problem is not immediately apparent.
• Pertussis epidemics are cyclical, occurring every 3-5 years. These peaks and troughs complicate the development of epidemiological studies.
What this means is that large-scale Phase III efficacy studies, in which disease is used as the endpoint, are not feasible. Also, formal correlates of protection have not been identified.
The PERISCOPE Project started in March 2016 and is designed to respond to some of these issues. Funding is made available by a public private consortium involving the Bill & Melinda Gates foundation, the European Union, and European Federation of Pharmaceutical Industries and Associations (EFPIA) partners, and in this case, GlaxoSmithKline and Sanofi Pasteur. In total, there are 22 partners in this project.
The strategic objectives of this partnership include the following:
• Foster expertise and increase capacity in Europe to evaluate new pertussis vaccines both in clinical and preclinical models.
• Identify early biomarkers of long-lasting protective immunity to pertussis in humans. (This step will accelerate and de-risk clinical development of next generation pertussis vaccines.)
• Investigate the impact of maternal vaccination on infant response to pertussis vaccination.
The problem is that there is no one single study design that addresses all questions about the pertussis vaccine. For example, in PERISCOPE, the results of preclinical studies using the baboon or mouse models and addressing disease and colonization endpoints or immunogenicity do not perfectly model human infection and disease.
By comparison, controlled human infection studies provide information on colonization but not disease endpoints. Such studies, however, do provide information on immunogenicity endpoints. Also available are booster vaccination studies and infant vaccination studies providing data on immunogenicity, as well as safety information.
Finally, there are patient studies, such as household contact studies where immunogenicity can be correlated to disease endpoints. From these studies, it will be seen that what is needed is integration of evidence from clinical and preclinical studies to support a new vaccine registration.
PERISCOPE addresses these issues by developing novel, functional antibody and cellular assays and employing cutting-edge methods to characterize innate immune responses and cell-mediated systemic and mucosal immunity. PERISCOPE combines two major industrial partners with public researchers from academic and public health institutes and small and medium-sized enterprises with expertise in clinical trials, vaccinology, immunology, molecular microbiology, challenge models, and bioinformatics.
Andrew Gorringe, PhD, from Public Health England and the Research and Development Institute at Porton Down, Wiltshire, England, said, “Vaccines have greatly reduced the incidence of pertussis, but it remains the most prevalent ‘vaccine preventable’ disease. This is an exciting period for pertussis vaccine research as we find new ways to understand the immunity that protects from both infection and disease. The PERISCOPE project provides a collaborative environment that combines expertise across Europe to provide a route to the development of new, more effective vaccines.”
GSK and Sanofi Pasteur have cofunded the PERISCOPE Project. Dr. Diavatopoulos made no other financial disclosures.