The development of a vaccine is the ultimate treatment against this virus. This vaccine must duplicate the role played by the natural immunity. Vaccine program must include the prevention of moderate to severe disease. Over the last 2-3 decades many vaccines have been developed of which the 'jennerian' vaccines were the first to be introduced. These were ineffective because they did not provide complete protection against the virus. As a result, non-jennerian based vaccines were introduced. These were neonatal, cold-adapted and attenuated human strains of rotavirus. Some other vaccines used baculovinus expressed virus-like particles or naked DNA. Vaccine development is a huge investment and it depends on three main factors namely efficacy, safety and cost. The key success to a vaccine program is developing a robust surveillance system that can generate comprehensive and systematic data on the disease burden and accurately forecast the vaccine demand. A similar case was seen with the rotavirus vaccine. A large number of deaths were recorded under the age of five and this was caused due to the rotavirus. These records serve as evidences and help in decision makers to allocate resources and funding.
Rotashield was the very first vaccine against rotavirus and this was removed almost instantly from the market due to the intussuception issues. The vaccines made today differ from Rotashield as the benefits outweigh the risks. The most critical issue to develop a vaccine is the cost of their purchase and its affordable price. GSK has now developed a multi-tiered pricing system that addresses some of the concerns of developing countries. Another profitable road is the partnership of the private and public sector to help in the vaccine funding. Some of the key players are WHO, RVP, UNICEF, SVI. These along with Merck and GSK help in solving the financial issues for rotavirus vaccines.
Currently there are two vaccines in the market against rotavirus. They are Rotateq manufactured by Merck and Rotarix a monovalent vaccine manufactured by GSK. Rotateq consists of five reassortment rotaviruses, four of which express VP7 proteins namely G1, G2, G3 or G4 from human rotavirus parent strain, and VP4 from the bovine rotavirus parent strain (P7). The fifth virus strain is P1A from the human rota parent strain and there is an outer capsid protein GG from the bovine rotavirus strain. Rotateq is started when the child is 6-12 weeks of age and given in three oral doses at 1 to 2 month intervals. The clinical trials for rotateq were a success and this was conducted with people from over 11 countries of which people from America constituted for more than 80 percent. The trial tested not only for intussusception but also immunogenicity and efficacy of the vaccine. After some initial glitches the vaccine proved to be successful against rotavirus infection by 96%. With this accomplishment it was licensed in February 2006 by the FDA for use among infants in the USA and is still widely used as a three dose scheduled at 2, 4 and 6 months of age. Post marketing studies is still being carried out in the United States. Data available till date does not suggest any association between Rotateq and inssuception.
Another successful vaccine was a live attenuated human rotavirus vaccine. This vaccine is a P1AG1 strain and codes for most of the human rotavirus VP7 and VP4 antigens. Cloning and tissue culture passaging of parent modified this 89-12 vaccine strain, now called as Rotarix, manufactured by GSK. The overall protection against the virus was noted to be 85 percent and there was no case of intussception seen. This vaccine was first licensed in Mexico and Dominican Republic in 2004. This vaccine is now used in over 90 countries worldwide. The vaccine is administered in two oral doses at 2 and 4 months of age. Manufacturer monitors post marketing safety of Rotarix, and vaccine is monitored for its effectiveness and the serotype distribution worldwide.
The vaccines that are currently available are very expensive and is affordable only by the upper class and middle income groups, so the challenge is to develop a vaccine which is accessible to all, affordable to all, safe and cheap. PATH a non-profit organization is encouraging and collaborating with emerging vaccine manufacturers for the development of more feasible vaccines against rotavirus. PATH has collaborated with China and India in a view of developing two promising vaccines that are safe, effective and inexpensive. The organization is also helping the development of bovine human reassortant vaccine that is available to all manufacturers. Bringing back the Rotashield onto the market is another idea considered. Rotashield was voluntarily removed from the market in 1999 when the intussuception was identified. More trials and research is now being done on this vaccine to bring it back to use. BioVirx has licensed this vaccine in an aim of gaining marketing and regulatory approvals and to target low-per-dose price in order to make it available to all. Neonatal vaccines based on strains of rotavirus that enter newborn nurseries in hospitals where they become established are also considered. Phase 1 and II trails conducted in Australia showed an immune response of 46% in infants associated with protective efficacy of 56% against the rotavirus. The obstacle yet to overcome is the vaccine culture constrained strength per dose. To sum it up vaccines against rotavirus are being developed worldwide but how long will they take and if they will be affordable to all is a question unanswered.
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