Rotavirus is the leading cause of acute gastroenteritis among infants and young children worldwide. Rotavirus is estimated to account for one-third of the estimated 1.3 million deaths yearly from diarrhea [ 1-3 ]. In the prevaccine era, rotavirus accounted for 2.7 million illness episodes and around $1 billion annually in medical costs in the USA [ 4 , 5 ].

Rotaviruses are 70 nm double-stranded RNA icosahedral viruses belonging to the family Reoviridae . The virus is composed of an outer and inner capsid and a core. Three major structural proteins (VP 4, VP 6, VP 7) and one nonstructural protein (NSP4) are of interest in vaccine development. The exact mode of transmission of rotavirus is unknown. It is assumed to be spread from person to person contact or aerosolized respiratory droplets. Incubation period is short, usually less than 48 h. The virus replicates in the mature villous epithelial cells of the small intestine causing malabsorption. The nonstructural protein (NSP4) acts as an enterotoxin causing diarrhea [ 6 ]. Severe gastrointestinal illness by rotavirus mainly occurs in children 3–24 months [ 7 , 8 ]. Infection during first month of life provides IgA-mediated protection against moderate-to-severe illness on reinfection. Rotaviral infection may be asymptomatic or cause self-limited diarrheal ill ness or result in severe dehydrating diarrhea complicated by electrolyte imbalances, metabolic acidosis, and multiorgan involvement. Diagnosis is made by detection of rotavirus antigen in stool by enzyme-linked immunosorbent assay.

The first rotavirus vaccine , RotaShield (RRV-TV, rhesus-based tetravalent rotavirus vaccine), was introduced in the USA in 1998 but was withdrawn from the market a year later because of its association with intussusception 3–14 days after administration of first dose of vaccine. Currently there are two rotavirus vaccines licensed in the USA—RV5 (RotaTeq) and RV1 (Rotarix). RotaTeq is a live oral vaccine licensed in 2006. It contains five reassortment rotaviruses developed from human and bovine rotavirus strains. The vaccine viruses are suspended in buffer solution. Rotarix is also a live oral vaccine , licensed in 2008. It contains one strain of live attenuated human rotavirus type G1P1A [9]. The vaccine is a lyophilized powder that is reconstituted before administration. Both these vaccines contain no preservatives or thimerosal. The vaccine effectiveness is 74–87 % against any rotavirus gastroenteritis and 85–98 % in severe rotavirus gastroenteritis. Both vaccines significantly reduce physician visits, hospitalization, and overall morbidity and mortality.

The ACIP recommends [ 10 ] routine vaccination of all infants, administered as a series of either two doses of RV1 or three doses of RV5 beginning at 2 months of age or as early as 6 weeks with sub sequent doses in the series separated by 1–2 months. The maximum age for any dose is 8 months. The only contraindication to the vac cine is a severe allergic reaction to vaccine components, a history of intussusception, or severe combined immunodeficiency syndrome. The common side effects were vomiting, diarrhea, fever, and irritability and no serious reactions have been reported so far.

Rotavirus disease among infants and young children significantly decreased after the introduction of the vaccines. The vaccine prevents an estimated 50,000 hospitalizations among US infants and indirectly protects older children and adults. The CDC uses the National Respiratory and Enteric Virus Surveillance System (NREVSS) to estimate burden of the disease and disease trend and evaluate the impact of vaccination in the USA.

References
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[10]. Centers for Disease Control and Prevention (2014) ACIP rotavirus vaccine recommendations. MMWR