Table 1.

Development and pre-clinical assessments of notable live-attenuated oral rotavirus vaccines.

Vaccine	Strain	Developer/Manufacturer	Type of Vaccine/Status	Vaccine Development and Assessment
From animal rotavirus strains (first generation of rotavirus vaccines)
RIT4237 (monovalent)	G6P6[1], BRV NCDV strain	SmithKline-RIT (Rixensart, Belgium)	Jennerian, but withdrawn	About 154 cell culture passages with high titre value of over 108 TCID50/mL, first to be tested in human, higher efficacy in the developed countries, negative gastric effect, breast milk did not affect but suppressed by OPV [154].
RRV-MMU (monovalent)	G3P[5] RRV strain	National Institute of Health (NIH)	Modified Jennerian-based vaccine, but withdrawn	Passaged 9 and 7 times in monkey kidney and foetal rhesus lung cells, respectively, with 105 PFU/dose titre level, reactogenic for fever, very virulent and later used as a backbone for RotaShield® [81,155].
WC3 (monovalent)	Wistar calf strain G6P[7]	Institut Merieux/Wistar Institute	Jennerian, but withdrawn	Passaged 20 times with 107 PFU/mL titre value, less efficacious compared with RRV-MMU but later used as a backbone for RotaTeq® [91,156].
LLR-37 (monovalent)	Lanzhou lamb-derived rotavirus G10P[15]	Lanzhou Institute of Biological Products (China)	Jennerian, licensed for use in China only since the year 2000	Ovine attenuated vaccine, efficacious in 2 doses at 2 months and 2 years, replicate with faecal shedding within 15 days post-vaccination. Over 60 million doses rolled out as at the end of 2014 [157,158].
Animal–human reassortant strains (second generation of rotavirus vaccines)—Jennerian-based vaccines
RotaShield® (RV4)	Tetravalent human–rhesus reassortant (G1-G4)P7 [5]	Wyeth (Madison, NJ, USA)	Jennerian and first licensed to be used in the USA by 1998 but withdrawn in 1999 due to IS, but now in phase II trials for neonatal administration in Ghana	First reassortant prototype, stable at 25 °C, formulated with G1, G2, and G4 VP7 antigens on rhesus G3P[5] backbone, reactogenic for fever, formulated with 4 × 104 PFU/mL with two doses and caused IS but tested to be safe in neonates in Ghana [159], which might favour its re-introduction [63,160].
RotaTeq® (RV5)	Pentavalent human–bovine reassortant G1-G4+P7 [5]; G6+P1A [8]	Merck & Co., Inc. (Burlington, MA, USA). Presented as a 2.5 mL liquid vaccine suspended in a buffer and administered via a squeeze tube. Scheduled as 3Ds	Jennerian, pre-qualified for global use since 2008 but first licensed in 2006. Usually co-administered with DPT 1, 2, and 3 vaccine doses	It is formulated with 2–2.8 × 106 PFU/mL with immunogenicity tested in 70,000 infants [161]. The overall efficacy was 95% against (G1–G4, G9)P[8] and displayed heterotypic protection against G2P[4]. Shedding and diarrhoea were observed in <1% infants [162,163]. Similarly, high efficacy was reported in 34,035 vaccinated infants from 11 countries across Latin America, America, and Europe [123]. VE increased with severity but decreased over 2 years of follow-up in Africa and Asia with 6674 infants from Ghana, Kenya, Mali, Bangladesh, and Vietnam (4705 African and 1969 Asian) [164]. The vaccine, however, requires cold-chain (2–8 °C) storage and transportation.
BRV-TV or BRV-PV	Bovine–human tetravalent reassortant G1-G4+P7 [5]; G1-G4+G9-P7 [5]	Biotecnics Instituto Butantan Shantha Biotecnics Limited Serum Institute of India (Pune, India) Wuhan (China)	Phase I trial in Brazil Phase II/III trials in India Phase III trial in China -	Started by Wyeth but discontinued at the same time RotaShield® was withdrawn; however, the prototype has been licensed by NIH to Brazil, India, and China [165].
RotaSIIL® (BRV-PV)	Pentavalent human–bovine reassortant serotypes G(1–4) and G9	Serum Institute of India Pvt Ltd. (SIIPL). Presented in two forms–2.5 mL reconstituted lyophilised vial and 2.5 mL prepared liquid vial. Each scheduled as 3Ds	Pre-qualified for global use in 2018 but licensed for use in India since 2016. Co-administered with DPT 1, 2, and 3 vaccine doses	World’s first cost-effective, thermostable vaccine which can be stored without refrigeration or below 25 °C. It is a bovine UK rotavirus strain from NIH (USA), which was reassorted with human VP7 genome encoding segments [166]. The vaccine has a lifespan of 20 months at 37 °C or 7 months at 45 °C.
Human rotavirus strains (second generation of rotavirus vaccines)—modified Jennerian-based vaccines
Rotarix® (RIX-4414)	Monovalent human strain G1P1A [8]	GlaxoSmithKline, GSK (Belgium). Presented in two forms. First, as 1 mL liquid vaccine with oral applicator or as a squeeze tube. Secondly, as 1.5 mL freeze-dried reconstituted with buffer and used with an oral applicator. Scheduled as 2Ds	Pre-qualified for global use since 2009 but first licensed in 2006. Co-administered with DPT 1, 2, and 3 vaccine doses	The most extensively used vaccine that was initially developed in Cincinnati, USA. The parent strain was first isolated from a child with natural RVI during the serotype 1 outbreak in 1988–1989 [91] and passaged 45 times in MRC-5 cells to remove the infectivity. Initially developed by Avant Immunotherapeutics Inc. Massachusetts, USA but licensed to GSK for further modification [167]. With 60,000 infants, Rotarix® induced >90% efficacy with significant homotypic and heterotypic protection against HRV strains, reaching 100% efficacy against a more severe case [127]. Summarily, Phases I–III trials with over 70,000 children proved the vaccine was non-reactogenic, well-tolerated, effective at first dose, but increased seropositivity rate after the second dose, not associated with IS but provided >85% protection against moderate to SRVGE, and reduced GE-related hospitalisation by >40% in Latin America and >75% in Europe [168,169]. This vaccine also requires cold-chain facilities (2–8 °C).
Rotavac®	Human neonatal strain 116E G9P[11]	Bharat Biotech International Limited (India). Presented as a 0.5 mL liquid vaccine with a separate dropper	Pre-qualified for global use in 2018 but licensed for use in India since 2014 [170]. Co-administered with DPT 1, 2, and 3 vaccine doses	It is a naturally occurring reassortant strain G9P[11], containing one BRV gene P[11] and ten HRV genes [60] at 105 FFU/dose formulation, taking in 3 single doses at 4 weeks interval starting from 6 weeks of age. This vaccine was licensed and introduced into the NIP (National Immunisation Program) of India by 2014 [60]. This vaccine must be stored at −20 °C.
Rotavin-M1®	Human strain G1P1A [8]	Centre for Research and Production of Vaccines and Biologicals - Polyvac (Vietnam)	Licensed to be used in Vietnam since 2007	It was derived from an attenuated G1P[8] strain (KH0118-2003) isolated from a Vietnamese infant, passaged in Vero cell at 106.3 FFU/dose, given in 2 doses (2 months apart) or 3 doses (1 month apart), safety, and immunogenicity tested in 160 infants with rotavirus-specific IgA seroconversion rate of 73% vs. 58% in Rotarix® and rotavirus shedding between 44% and 48% vs. 65% for Rotarix®. Over 500,000 doses already rolled out. The vaccine must be stored at −20 °C [19].
RV3-BB	Human neonatal strain G3P2A [6]	Murdoch Children Research Institute, Australia Biofarma, Indonesia	Phase III trial in Indonesia	RV3 is based on a neonatal G3P[6] strain from Melbourne. A Vero cell-adapted derivative of the strain RV3-BB grew to a higher titre 8.3 × 106 FFU/mL and was more immunogenic than the parent strain RV3 [171]. The Phase IIa trial with 3Ds in New Zealand showed 63% neonate and 74% infant with IgA seroconversion and shedding was 70% in the neonate and 78% in the infant. The vaccine was well-tolerated and immunogenic [172]. Analysis in the Phase IIb in Indonesia showed the efficacy of 75%, 51%, and 63% in the neonate, infant, and combined groups against SRVGE, respectively [173]. Vaccine response/“take” of RV3-BB was 94% and 99% in the neonatal- and infant-scheduled groups, respectively [173].

D = dose; DPT = Diphtheria, Pertussis and Tetanus; IS = intussusception; NIH = National Institute of Health; SRVGE = severe rotavirus gastroenteritis; IgA = immunoglobulin A; FFU = focus-forming unit.