Drugmaker Sanofi Pasteur has announced the world’s first dengue vaccine could come in the second half of 2015. This is potentially huge news for India, where a very large percentage of dengue infections occur. PRITHA CHATTERJEE explains.
What has Sanofi announced?
On November 3, the France-based drugmaker announced that its vaccines division had published in The New England Journal of Medicine the results of the Final Landmark Phase III Clinical Efficacy Study in Latin America of its dengue vaccine candidate. Overall efficacy against any symptomatic dengue disease was 60.8 per cent in children and adolescents between ages 9 and 16 who received three doses of the vaccine,
Sanofi said. According to the company’s release, analyses had shown a 95.5 per cent protection against severe dengue and an 80.3 per cent reduction in the risk of hospitalisation during the study.
Why is a dengue vaccine needed?
Dengue is a mosquito-borne disease caused by a virus, with four strains. The mortality associated with the virus is seen from a complication called Dengue Haemorrhagic Fever (DHF), characterised by a sharp drop in platelets. With no specific treatment available for this condition, the management of dengue has been largely preventive, through anti-mosquito activities, or symptomatic, where doctors treat patients for the symptoms. A vaccine, according to the WHO, “would, therefore, represent a major advance in the control of the disease”.
How close are we realistically?
Sanofi has said it would file for registration of its vaccine candidate and, “subject to regulatory approval, the world’s first dengue vaccine could be available in the second half of 2015”. According to the WHO, among the several clinical trials currently under way, Sanofi Pasteur’s tetravalent vaccine, which would provide protection against all four strains of the virus, is at the “most advanced clinical development stage”.
So why should we be cautious?
WHO said this month that it would be advised by its Strategic Group of Experts on “any recommended use of dengue vaccines”. The key issues would include “parameters around programmatic sustainability including dose scheduling”. According to WHO, the latest trials have “raised the question on whether or not three doses of the vaccine are required to provide lasting protection in endemic sittings”, which would require “further investigation in post licensure studies”. And “any recommendations for use will only be issued following licensure of the vaccine by a functional National Regulatory Authority (NRA)”.
How will the vaccine work?
Sanofi Pasteur’s tetravalent vaccine has been made with live attenuates of each strain of virus in a restricted and controlled amount, which is expected to just trigger the body’s immune response system to a level where immunity is developed, but the strain does not actually cause the disease. When the body encounters the virus in the atmosphere, it is expected that the immunity which has been exposed to the virus in the controlled amount, will trigger the same protective response system.
How big a threat is dengue to India?
According to WHO, dengue threatens over 2.5 billion people worldwide, including an estimated 500,000 who are hospitalised every year from the disease. Between 2 and 3 of every 100 people who contract dengue end up dying from it. According to a large study published in 2013, in 2010, an estimated third of all dengue infections were in India, and the situation has worsened since. According to Health Ministry data, the number of dengue cases jumped 500 per cent from 12,561 in 2008 to 75,808 in 2013, while the number of deaths from the disease more than doubled from 80 in 2008 to 193 in 2013.
Western and southern India, Delhi and West Bengal are the dengue hotspots in India. In 2013, the most cases were reported from Kerala (7,938), followed by Orissa (7,132) and Karnataka (6,408). The most deaths, however, occurred in Maharashtra (48), followed by Kerala (29) and Punjab (25). Both the disease and deaths are, however, suspected to be under-reported, and some experts feel the incidence of dengue in India could be up to 300 times higher.
What is the situation this year?
Up to October 29 this year, 21,772 cases had been reported countrywide, with 48 deaths, according to the Health Ministry. Data compiled for Delhi until Monday showed 438 cases and 2 deaths in 2014 so far. Eleven were confirmed dead in Mumbai until Friday. At least nine resident doctors of J J Hospital, Mumbai’s largest state-run hospital, have contracted the disease in the last two months. The post-monsoon months from August to October see the largest number of dengue infections in the country.