Safety, Reactogenicity and Immunogenicity of Heat-stable Rotavirus Vaccine (HSRV) in Adults and Infants

Rotaviruses are the leading cause of severe, dehydrating diarrhea and related deaths in children aged less than 5 years worldwide and are reported to infect nearly every child by the age of 5 years. About 90% of all rotavirus-associated fatalities occur in low income countries in Africa and Asia and are related to poor health care. In most low income countries in Asia and Africa, rotavirus epidemiology is characterized by one or more periods of relatively intense rotavirus circulation against a background of year-round transmission, whereas in high income countries with temperate climates a distinct winter seasonality is typically observed. In 2008, WHO estimated approximately 453,000 (420,000-494,000) rotavirus gastroenteritis (RVGE) associated child deaths worldwide. These fatalities accounted for about 5% of all child deaths with a cause-specific mortality rate of 86 deaths per 100,000 population aged less than 5 years. In view of high global RVGE burden, the World Health Organization (WHO) on 5th June 2009, recommended the inclusion of rotavirus vaccine in all the national immunization programs.

As in other Asian countries, Rotavirus infection is a significant cause of illness and hospitalizations in Bangladesh with approximately 2.4 million cases being reported every year and nearly two-thirds of all diarrhea-related hospitalizations in children under age 5. While progress has been made in reducing diarrhea-related deaths among children, it is still one of the leading causes of illness among children under 5 in Bangladesh. About half of all rotavirus hospitalizations were among infants age 6-11 months, Rotavirus vaccines could have a powerful public health impact if introduced into Bangladesh's national immunization program.

The basis for developing a rotavirus vaccine rested on the observation that wild-type rotavirus infection immunized children against subsequent disease. The immunity from wild-type infection does not prevent all subsequent infections; however, it provides nearly complete protection against severe disease and substantial protection against mild disease. The five most prevalent rotavirus genotype/serotype combinations are G1P1A[8], G2P1B[4], G3P1A[8], G4P1A[8], and G9P1A[8].

Currently, RotaTeq® and Rotarix® are the two WHO prequalified vaccines which are stable for recommended duration at storage temperature between 2-8 °C. Studies indicate that if these currently available vaccine, for example RotaTeq®, is inadvertently exposed or stored at temperatures above 8 °C, the potency is maintained for the maximum exposure of 48 hours at 9 °C to 25 °C or for a bare 12 hours at 26 °C to 30 °C. However, if RotaTeq® vaccine is exposed to temperatures above 30 °C, the vaccine has to be discarded due to lost potency. There is limited data to suggest that if the vaccine is inadvertently exposed to temperatures below 0 °C, the potency of the vaccine is maintained. Another, currently available freeze dried vaccine i.e. Rotarix® vaccine exhibits stability with a shelf life of 36 months at 2 °C to 8 °C.

Hence these vaccines do not possess enough thermostability profile suitable for storage outside cold chain for any meaningful amount of time and needs to be stored and transported under refrigeration. It is very difficult to maintain the cold chain required to conserve the vaccine potency particularly in developing and low income countries, resulting in large amount of vaccine being wasted and in worst case scenario, not providing protection against rotavirus infection to potential recipients. Many other existing vaccines do exhibit some degree of thermostability, however, the existing licensed vaccines possess shorter period of thermostability (e.g. VVM 7 or VVM 14) which fails to address the issues in developing countries especially in region of extreme climatic conditions, reaching up to 40 °C.

Heat Stable Rotavirus Vaccine is a lyophilized heat stable rotavirus vaccine comprising of five live reassortant rotaviruses in RotaTeq®. The parent strains of the reassortants were isolated from human and bovine hosts. Four reassortant rotaviruses express one of the outer capsid proteins (G1, G2, G3, or G4) from the human rotavirus parent strain and the attachment protein (P7) from the bovine rotavirus parent strain. The fifth reassortant virus expresses the attachment protein, P1A (genotype P[8]), referred to as P1[8], from the human rotavirus parent strain and the outer capsid protein G6 from the bovine rotavirus parent strain. These reassortants were suspended in stabilizer solution which was then lyophilized to obtain thermostable cake. This lyophilized cake will be reconstituted using a reconstitution buffer. There are no preservatives or thimerosal present in the vaccine. The new heat stable rotavirus vaccine (HSRV) formulation offers higher titer value even at extreme temperature conditions up to 45 °C for prolonged periods of time. This new heat stable formulation (HSRV) could be transported in non-refrigerated supply chain significantly reducing the cost and complications associated with transporting vaccine to remote corners of the developing world. The bulk of reassortants virus have been procured directly from Merck and Co., USA, currently licensed in USA and many countries as liquid formulation RotaTeq®, offering an easier regulatory path for new heat-stable rotavirus vaccine licensure \& WHO prequalification. Heat-stable rotavirus vaccine (HSRV) has a potential to sustain high temperatures frequently encountered in regions where majority of rotavirus burden exists and has potential to partially or completely eliminate cold chain dependence.

The aim of the current study is to assess the safety and reactogenicity of a single dose of Hilleman Labs.' oral live attenuated HSRV vaccine in healthy adults aged 18 years to 45 years followed by safety \& immunogenicity evaluation in infant population 6-8 weeks of age. In current study, adult subjects will either receive a single dose of oral live attenuated HSRV vaccine or placebo at Day 0. There will be a safety follow-up for all subjects for a period of 14 days after vaccination. The investigators intend to establish the safety of HSRV in healthy adults prior to testing in infant population. Acceptable safety data from the adult cohort will allow enrolment of subjects in the infant cohort, after approval from study DSMB.