Development and Evaluation of Live, Attenuated Rotavirus Vaccines

Infectious diseases account for 64% (4.879 million) of the 7.6 million deaths occurring during the first 5 years of life in 2010, with the 3 leading infectious diseases causes being pneumonia (1.396 million or 18.3% of total deaths), diarrhea (801,000 or 10.5% of total deaths) , malaria (564,000 or 7.4% of total deaths) with the largest overall mortality in Africa and S.E. Asia. Rotaviruses (RVs) have emerged as the single most important cause of severe diarrhea of infants and young children in both developed and developing countries accounting in 2008 prior to the introduction of RV vaccines for about 453,000 deaths in the under 5 yr age group, mostly in developing countries. RVs are egalitarian as they infect infants and young children with similar frequency in countries with high or low socio-economic conditions but the consequences are very different as described earlier. We developed an oral, live, attenuated quadrivalent RV vaccine to protect against the 4 epidemiologically important serotypes (G1-4).The vaccine was comprised of each of the following 4 serotypes: rhesus RV (RRV), a G3 strain, (the Jennerian approach), and 3 human RV-RRV reassortants, each possessing 10 RRV genes and a single human RV gene that encodes VP7 (a major outer shell protein) that is responsible for serotype G1, G2, or G4 specificity (the modified Jennerian approach). Following clinical studies which demonstrated the vaccine's safety, immunogenicity and efficacy especially against severe diarrheal disease, the ACIP, which advises the CDC, recommended its routine use for infants at 2, 4, and 6 months of age. in Aug 1998 the FDA granted a Biologics License for the vaccine (RotaShield RRV-TV) to Wyeth Labs. However, in July 1999, after over one million doses had been given to an estimated 600,000 infants, the CDC recommended suspending further vaccination because post-licensure surveillance suggested that the vaccine was linked with intussusception (IS). Following additional CDC studies, in Oct 1999 the ACIP withdrew its recommendation because of additional data which supported this link. In conjunction with these events, Wyeth Labs withdrew the vaccine. However, later analysis demonstrated that age of vaccination was a critical factor in the link with IS. In the CDC case-control study, vaccinees who were 90 days of age or older at the time of the first dose developed 81% of all cases occurring within 2 weeks of vaccination, even though they received only 38% of all first doses. Thus, catch-up vaccination of older infants during the age period of high vulnerability to IS (3 or 4 to 9 months of age) contributed disproportionately. There are questions regarding the vaccine's actual attributable risk of IS, a risk estimate that has ranged widely with a consensus figure of 1 in 10,000. Because the RRV-TV vaccine was associated with a transient and characteristically low grade fever in up to about one-third of vaccinees and the knowledge that bovine RV-based vaccines were characteristically non-reactogenic, in parallel with RRV-TV vaccine studies,we had initiated studies with individual human-bovine rotavirus (UK) reassortants and found that they were safe and immunogenic. These were followed by clinical studies of the 4 reassortants combined, a formulation that represented the 4 important RV serotypes, and showed that this vaccine (BRV-TV) was also safe and immunogenic. In a Wyeth-Univ.of Tampere-NIH collaborative clinical study in Finland, in which the RRV-TV and BRV-TV were evaluated in a two-dose schedule, the BRV-TV and RRV-TV induced a high level of protection against severe RV diarrhea over two RV seasons. The BRV-TV vaccine did not induce a significantly greater number of febrile episodes after vaccination when compared to controls whereas RRV-TV did. In addition, another Wyeth-University of Tampere-NIH study in Finland evaluating the effect of administering RRV-TV vaccine or placebo in 3 ddifferent schedules, showed that neonates did not develop a febrile response after the neonatal dose. In addition, the neonatal dose induced significant protection against the development of a febrile response when infants received a second dose at 2 months of age. We have pursued our continued interest in RV vaccines especially for the developing countries where the toll from diarrheal diseases is immense. The NIH granted an exclusive license to BIOVIRx, Inc., a U.S. company (which was later transferred to the non-profit International Medica Foundation (IMF). This effort with RRV-TV stalled initially but was revived when funding became available from the IMF. Thus, a quadrivalent RRV-TV vaccine (RotaShield) was produced by The IDT Biologika GmbH in Germany, and became available in 2009 for clinical trial. A placebo-controlled phase II safety and efficacy trial began with RotaShield in Ghana on Aug. 28, 2009. By the end of Nov 2009 almost 1000 infants were given the 2nd dose of RotaShield or placebo: the 1st dose within the first 29 days of life and the 2nd dose before 60 days of age with a minimum interval of 3 weeks. The study period ended at the end of November, 2010 when the final participant reached an age within two weeks of the first birthday. In the per-protocol analysis, which included almost 900 study individuals, the vaccine demonstrated promising efficacy against pooled G1-G4 diarrhea. It also induced a 4-fold or greater IgA ELISA antibody response in over 50% of of a subset of vaccinees (3.4% of controls). In addition, efforts to implement our 2nd generation vaccine, the human RV-bovine RV reassortant vaccine (BRV) for the developing countries have advanced. The NIH OTT initially granted licenses to develop the bovine RV-based vaccine to 8 institutions,1 in the U.S. and 7 in developing countries (Brazil, China and India).Three of the 8 have engaged in vaccine production and in various stages of early clinical trials (one of these was suspended- contamination) and a fourth licensee is producing pre-vaccine materials. Requests for licenses have continued with the OTT granting licenses for BRV vaccine to an additional 2 laboratories in 2009 and 2 in 2010 in China with pending requests or inquiries for licenses by additional labs in China and one in India. An additional lab in Korea has expressed interest in the human-porcine reassortant RV vaccine candidate developed by Dr.Hoshino. LID serves as an unofficial reference lab for this program performing various functions (e.g. ranging from temperature stability, to sequence analysis, etc). <P> We are proposing that the 2nd generation RV vaccine be comprised of 6 serotypes (G1-4, 8 and 9) as a universal vaccine or as a specifically designed vaccine for different areas of the world. The proposed manufacture of the vaccine in developing countries should result in its availability at low cost, which would facilitate its implementation there. Our goal of vaccine implementation for the developing world was given an unsolicited boost, when we were notified in Oct 2006 by PATH that the Gates Foundation had approved their application with funding '... to support the process and clinical development of the NIH bovine rotavirus vaccine through Phase 2 at two selected manufacturers; and address product development challenges relevant to all emerging manufacturers of this vaccine.' This grant has been extended through 2012, with a further extension in deliberation. In addition, in Nov 2010 PATH received a new grant from the Gates Foundation which will support a large phase 3 trial of one of our licensees in India of a pentavalent BRV vaccine. Its implementation is pending. In 2010 PATH received a grant from the Dep't for Int'l Dev (DFID), which in part is for support of a reference lab in Vellore, India for BRV vaccine candidates which will '...provide technical support and training on immunological assays to four BRV producers