The Dengue Vaccine

Friday, 23/09/2016

Dengue fever is a disease spread to humans by mosquito bites, and is caused by one of four types of dengue viruses. The symptoms caused by Dengue fever are similar to those caused by a severe flu.
The Dengue virus is called DEN V1,DEN V2, DEN V3, DEN V4 and a strain that is still under research that is DEN V-5. This diseases in most cases does wear off by itself and doesn’t cause massive damage as it behaves like a normal viral fever, the symptoms are highly similar and the cure during the initial stages is also.
India has shown a growth in the number of registered dengue cases, which have steadily increased from 6259 in 2010 to 10683 in 2015 according to the national vector borne disease control programme (NVBDCP).
Initially there was no vaccine which can be used to work against this dangerous virus and safe lives. As the technology and research started growing up scientist came up with a safe, efficacious and a cost-effective dengue vaccine that can be a supplementary measure in dengue prevention and control. Dengue vaccine is used to prevent dengue fever in humans.
The first dengue vaccine, Dengvaxia (CYD-TDV) was developed by Sanofi Pasteur. Cyd-tdv is a live recombinant tetravalent dengue vaccine.

There are three doses of the vaccine which are supposed to be given a space of one year. It has been registered for age group 9 to 45. This vaccine efficacy is only 30.2% and is not statistically significant.

2. Challenges
• Scientists have been unable to develop a vaccine for dengue in parts because the virus is very complex.
• It has four strains, so if a person gets infected with more than one type of dengue, the chances of one getting hospitalized due to it are extremely high.
• The fact that the development of this vaccine requires very expensive and time costing human testing. This a great challenge. There is no good animal model that can be used as a predictor as human dengue is quite unique.

However, elimination of dengue is not an overnight process even if a successful vaccine is developed. There are issues of supply as production capacity is limited. It is a costly vaccine. There are certain side effects of Dengvaxia’s that are systemic headaches, fatigue and light-grade fevers.

3. Current development in Dengue Vaccines
Tremendous efforts have been made for dengue vaccines and drugs.
• Indian scientists at the international centre for genetic engineering and biotechnology (ICGEB), Delhi have developed a Denv-2 e protein based non-infectious virus-like particle (VLP) using the yeast pitchia pastoris as the expression system. Since yeast expression system has the advantage of high yield, the VLP-based formulation can be an inexpensive vaccine for usage future, once its efficacy and safety are established.
• Scientists are focusing on the generation of a tetravalent vaccine as it aimed at providing long-term protection against all virus serotypes. Such a response would defend us against dengue febrile illness. It would also reduce or eliminate the risk of antibody-dependent enhancement which predisposes people to severe dengue.

A safe, effective and affordable dengue vaccine against the four strains would represent a major advance for the control of the disease and could be an important tool for reaching the WHO goal of reducing dengue morbidity by at least 25% and mortality by at least 50% by 2020. Approximately five additional dengue vaccine candidates are in clinical development, with two candidates (developed by Butantan and Takeda) expected to begin Phase III trials in early 2016.