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The international medical community has been unified in voicing the need for an effective, prophylactic rotavirus vaccine. Researchers at the National Institutes of Health (NIH) developed a monovalent vaccine against rotavirus in 1984. Two years later, when it was thought that a monovalent vaccine might not protect against all the clinically important strains of the virus, the NIH group developed the additional individual components of the current vaccine. In 1987, commercial development of the first effective vaccine began. An effective, oral rotavirus vaccine was developed for sale under the trade name RotaShield®. In clinical studies, it provided 91% protection against severe diarrhea due to rotavirus. RotaShield® rotavirus vaccine was the first rotavirus vaccine approved and licensed by the FDA for marketing in the United States and was launched in August 1998. At that time, RotaShield® rotavirus vaccine was also introduced into the routine schedule of immunizations by the Advisory Committee on Immunization Practices (ACIP) and the American Academy of Pediatrics (AAP). RotaShield® rotavirus vaccine is a Tetravalent Vaccine (RRV-TV) that is administered in three oral doses at 2, 4 and 6 months of age. The vaccine is formulated as a lyophilized (freeze dried) powder that is reconstituted before oral administration by the addition of a manufacturer-supplied diluent. The lyophilized vaccine and diluent, as supplied, are stable at room temperature and under refrigeration. RotaShield® rotavirus vaccine was evaluated in clinical trials in nine countries including Finland, United States and Venezuela, and was demonstrated to provide excellent protection. The trial in Finland demonstrated an efficacy of 68% against any diarrhea, 91% against severe diarrhea, and 100% against hospitalizations. Importantly, the vaccine was also efficacious when tested in Venezuela which demonstrated that the vaccine was consistently efficacious in trials in both developed and developing countries. The main adverse event reported in pre-licensure trials was fever, which was self-limited. In July 1999, RotaShield® rotavirus vaccine was voluntarily withdrawn from the market because of a possible, but as yet uncertain association with intussusception (a blockage of the intestine) that was observed as a result of large-scale surveillance of vaccinates in the United States. Since withdrawal of RotaShield® rotavirus vaccine from the market, it has been determined that the originally projected incidence of intussusception as a function of rotavirus vaccination with RotaShield® rotavirus vaccine is significantly less than what was first reported. The purported association between vaccination with RotaShield® rotavirus vaccine and development of intestinal blockage still remains to be completely defined. However, a recent publication in the Journal of Infectious Diseases has concluded that the vaccine did not increase the total number of cases of intussusception when it was used in the United States to vaccinate over 900,000 infants. It was also reported recently in the Journal of Infectious Diseases that in 433,222 infants that had been immunized with RotaShield, the intussusception rate was related to the age of the infant at the time they received the first dose of the vaccine.? These authors reported zero cases of intussusception in 71,058 infants receiving the first dose of RotaShield prior to 60 days of age and only 9 cases of intussusception in 268,202 infants that had receive their first dose of RotaShield prior to 90 days of age. RotaShield® rotavirus vaccine is not commercially available at this time. Its withdrawal from the United States market has left a large gap in the tools available to physicians to prevent deadly rotavirus infections in infants and children. BIOVIRx intends to be a worldwide provider of the RotaShield® oral rotavirus vaccine. Simonsen L, Viboud C, Elixhauser A, Taylor RJ, Kapikian AZ. More on RotaShield and intussusception: the role of age at the time of vaccination. J Infect Dis 2005;192:Suppl 1:S36-S43 |
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