Immunization highlights: 2012
Vaccine research and development
New results from RTS,S/AS01 malaria vaccine trial
In November 2012, the latest stage of the RTS,S/AS01 Phase 3 malaria vaccine trial was completed. WHO will make evidence-based recommendations in 2015. These recommendations will be based on the full results from the Phase 3 trial that will become available in 2014, including the site-specific efficacy and booster dose data. WHO recommendations are based on the input of its independent advisors.
For malaria vaccines, the Joint Technical Expert Group (JTEG) on malaria vaccines will draft candidate policy recommendations for joint review by the Strategic Advisory Group of Experts on Immunization (SAGE) and the Malaria Policy Advisory Committee (MPAC) in 2015.
RTS,S/AS01 may have an important role in some settings in sub-Saharan Africa, depending on the results in 2014. RTS,S/AS01 will be evaluated as a possible addition to, and not a replacement for, existing preventive, diagnostic and treatment measures, depending on the results that become available in 2014.
Status of dengue vaccine development
Dengue is a mosquito-borne flavivirus disease that has spread to most tropical and many subtropical areas. The disease is caused by four closely related viruses, the Dengue viruses 1-4. There are no specific dengue therapeutics and prevention is currently limited to vector control measures. A dengue vaccine would therefore represent a major advance in the control of the disease.
While no licensed dengue vaccine is available, several vaccine candidates are currently being evaluated in clinical studies. The candidate currently at the most advanced clinical development stage, a live-attenuated tetravalent vaccine based on chimeric yellow fever-dengue virus (CYD-TDV) developed by Sanofi Pasteur, has progressed to phase III efficacy studies. Results from a phase IIb efficacy study in Thailand were published in September 2012.
Based on the published data from the study, the safety profile of CYD-TDV is satisfactory for the reported observation period. In addition, antibody responses to each of the four dengue virus strains in the vaccine were observed in vaccinated subjects. This was the first study conducted to evaluate the efficacy of any dengue vaccine candidate against clinical dengue disease in a population naturally exposed to dengue, which represents a significant advance for the field of dengue vaccine research.
According to the WHO Technical Advisory Group on Dengue Vaccines in Late Stage Development, the published data from this phase IIb study do not yet prove nor disprove efficacy of CYD-TDV against disease caused by any of the four dengue virus serotypes. Further studies in larger populations and different epidemiological settings are needed. Phase III efficacy studies are currently underway in 10 countries in Asia and Latin America.
WHO continues to provide guidance to vaccine regulators and developers on issues related to the evaluation of dengue vaccines. WHO also continues to work with a wide range of stakeholders towards the goal of future licensure and use of a safe, effective and affordable dengue vaccine.