It was during the 1780 epidemic in Philadelphia when one of the founding fathers of US Benjamin Rush coined the term ‘break bone ever’ because of the crippling symptoms of dengue. For a disease that has no known cure till date, the news of a dengue fever vaccine brings fresh hope that numbers will now come down. French pharma major Sanofi cleared the use of the first dengue fever vaccine Dengvaxia in Mexico and there is a sense of accomplishment that all will be well.
Cases of dengue have been spiralling over the years and coupled with rising fear and anxiety as there is no conclusive treatment, a new vaccine then spells anticipation that perhaps now there will be a drop in both hospitalisations and mortality rates.
Staggering numbers as indicated by WHO show that the disease kills 22,000 people per year and dengue has become the fastest growing mosquito-borne disease with as many as 400 million people infected every year. Mexico, according to recent research published in the PLoS neglected tropical diseases journal – was reported to have 139,000 symptomatic and 119 fatal dengue episodes per year on average.
Back home India too is grappling with the deluge. Official data often underestimates the burden of the disease. But even so the registered numbers of dengue cases and deaths are high enough to warrant immediate attention. According to the national vector-borne disease control programme (NVBDCP) till November this year, India recorded 90,040 cases across the country and 181 deaths.
Delhi was the hardest hit this year with 15,730 registered cases and 38 deaths. Punjab had 13731 cases and 18 deaths while Haryana came a close third at 8066 cases and 12 deaths. This was against 40,571 dengue cases across the country in 2014 and 137 deaths while the year 2013 had 75,808 cases and 193 deaths. Last year however Maharashtra had the highest numbers with 8573 registered dengue cases and 54 deaths vis a vis Delhi that had 995 cases and three registered deaths. The official numbers however, are just the tip of an iceberg. Several go unreported.
However as experts in the private sector appeal to the government to allow the import of the vaccine, others prefer to tread cautiously. Some hard facts also need to be looked at as clearly clean up measures are painstakingly slow and research may take years before an indigenous vaccine against dengue fever is developed. A vaccine cannot just be the panacea but has to be looked at a fast emerging alternative where health systems are not adequately geared to deal with the disease and the infrastructure is groaning to combat the increasing colony of dengue breeding mosquitoes.
Dr Cecilia Dayaraj, Pune-based NIV scientist has in her report in the WHO South-East Asia Journal of Public Health (2014) pointed out that the when dengue first emerged in India during 1950-60s the disease was mild despite circulation of all four serotypes. The disease profile has changed and greater severity has been reported from the late 1980s. The presence of four serotypes – some which are virulent – then has become one of the complex challenges presented by dengue.
While protective immunity against the infecting serotype is lifelong, it lasts for only three to four months against other serotypes. A second infection often results in severe disease. Better patient management, increased diagnostic capabilities and better reporting has helped control the disease, Dayaraj has observed.
The achievements of scientists have been considerable and a vaccine in this direction is a welcome step, says Dr V N Mishra, former director of NIV who echoes the scientific community’s sentiments. “There are other concerns and we will have to wait for a year or two to assess the response to the vaccine in Mexico,” the expert pointed out.
When clinical tests were carried out by Sanofi on 40,000 people from 15 countries, India too was listed as one of them. Results proved efficacious on adults but trials on children have yet to be undertaken. The vaccine so far can be administered to children above nine and adults less than 45.
Researchers feel it will take several more years before the prevention tool is analysed, clinically tested and proven to be efficacious on the field to be administered to all age groups.
At Indian Council of Medical Research, experts feel that it will take time for the introduction of the vaccine at the community level. There should be data and sufficient number of studies that evaluate the vaccine is effected against the Indian serotypes of the dengue virus. To bring such a vaccine in the public health domain experts underlined that there should be no side effects and strong evidence that shows immunity against the virus. What is a must now is to sustain vector control programmes as the virus finds newer hosts to infect. The community also cannot take a back seat and has to be actively involved in containing this virus.