About Rotavirus
Rotavirus, discovered in 1973 A.D. is the leading cause of severe dehydrating diarrhea in children < 5 years of age, globally. It is responsible for 3.4% of all under 5 deaths, 37% of total diarrheal deaths, and 40% of total diarrhea-related hospitalizations. [1]
Rotavirus is a double-stranded RNA virus of the family Reoviridae. It is wheel-shaped under an electron microscope, hence its name. There are 9 species A-I of which Rotavirus type A is the most common.
The mode of transmission is via fecal-oral route (person-to-person or via fomites). During the first episode of infection, viruses are shed for several days in a very high concentration (>1012 particles/gram) in stool and vomitus. The incubation period is 1-3 days where vomiting and diarrhea occur. This either resolves in 3-7 days or leads to electrolyte imbalance and shock and ultimately death. Protective immunity develops after natural infection and is strongest against moderate-to-severe disease.
Prevention
A realistic goal for a rotavirus vaccine is to duplicate the degree of protection against disease that follows natural infection.
Goals for a Rotavirus vaccine:
- To duplicate the degree of protection that
follows natural infection
- To prevent moderate-to-severe disease but not a mild disease from rotavirus
- To reduce the disease burden
- To provide vaccines in developing countries where rotavirus mortality is high.
Attenuation of rotaviruses by oral vaccines may be achieved in several ways: [1]
- First-generation vaccines (Jennerian approach):
These early rotavirus vaccines were single-animal strains that were naturally attenuated in that they did not cause clinical disease in humans but conferred protection against subsequent infection with human rotavirus strains. They are available in trade names RI T 4237, RRV-MMU, WC3 (non-reassortant), and LLR, out of which LLR, is the licensed vaccine and the rest are discontinued today.
- Second-generation vaccines (modified Jennerian approach):
- Animal-human reassortant:
These reassortants contain an animal strain that incorporates additional genes from human strains by capitalizing on the viruses’ ability to reassert in vitro. They are available as Wa X UK, RRV-TV (Rotashield), and Reassortant WC3 (Rotataq). Out of these, Wa X UK is in active Phase I trial, Rotashield is withdrawn and Rotataq is the licensed vaccine.
- Human attenuated strains:
These are vaccines developed through attenuation of human rotavirus strains. They are available as M37, Rotatrix, and 116E of which, M37 is discontinued, Rotatrix is the licensed vaccine and 116E is in active phase I trial.
Two safe and effective vaccines are now licensed in 100 countries but used in 17 countries; Rotarix (RV1) and RotaTeq (RV5). In April 2009, WHO provided a recommendation for the global introduction of these vaccines in national immunization programs of developing countries worldwide. [2]
RotaTeq vaccine
It is manufactured by Merck and was licensed by the FDA in 2006. It is a pentavalent human-bovine reassortant live-attenuated, oral vaccine. This vaccine contains five live reassortant rotaviruses. It is administered in three oral doses at 1- to 2-month intervals beginning at 6 to 12 weeks of age. [3]
In a large clinical trial conducted primarily in the US and Finland, RotaTeq showed an efficacy of 98% against severe rotavirus gastroenteritis. Protection was good (88-100%) against all G1-4 and G9 serotypes. In the US, the field effectiveness of the vaccine was similar to that observed in the clinical trial. [4]
Rotarix vaccine
Rotarix vaccine is manufactured by GlaxoSmithKline and was licensed by the FDA in 2008. A live-attenuated human rotavirus vaccine was originally developed in Cincinnati, OH by tissue culture of a wild-type human rotavirus isolate. It is a monovalent vaccine and is administered at 2 and 4 months of age.
In a clinical trial conducted in 11 Latin American countries and Finland, the results demonstrated a protection rate of 85% against severe rotaviral gastroenteritis and 100% protection against the most severe dehydrating rotaviral gastroenteritis episodes. [1]
Vaccines in development
An Indian-made rotavirus vaccine, Rotavac, is in development, and its phase III trials.
Other vaccines are undergoing clinical trials like- human neonatal P[6]G3 strain, RV3, developed by Ruth Bishop and colleagues in Australia, a neonatal strain vaccine (G9P11) being developed by Bharat Biotech in India. These novel approaches are being pursued using animal models.
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References
- Dennehy P. Rotavirus Vaccines: an Overview. Clinical Microbiology Reviews. 2008;21(1):198-208.
- Burnett E, Yen C, Tate J, Parashar U. Rotavirus vaccines: current global impact and future perspectives. Future Virology. 2016;11(10):699-708.
- [Internet]. Who.int. 2021 [cited 22 March 2021]. Available from: https://www.who.int/immunization_standards/vaccine_quality/RotaTeq_Product_Insert.pdf
- Jiang V, Jiang B, Tate J, Parashar U, Patel M. Performance of rotavirus vaccines in developed and developing countries. Human Vaccines. 2010;6(7):532-542.
