Merck & Co., Inc said its rotavirus vaccine Rotateq reduced hospitalisations and emergency department visits caused by the G9P1A rotavirus serotype, by 100 per cent. The data is obtained according to a post-hoc analysis of healthcare utilization data from more than 68,000 infants in the Rotavirus Efficacy and Safety Trial (REST).

Rotateq is an oral vaccine and is indicated for the prevention of rotavirus gastroenteritis in infants and children caused by the serotypes G1, G2, G3 and G4 when administered as a three-dose series to infants between the ages of six to 32 weeks.

The prescribing information for Merck & Co., Inc.'s Rotateq (rotavirus vaccine, live, oral pentavalent), the only vaccine in the US to help prevent rotavirus gastroenteritis in infants and children caused by G1-G4 serotypes, now includes the data obtained from the REST, one of the largest pre-licensure vaccine clinical trials ever conducted.

G1, G2, G3 and G4 are four common circulating serotypes of rotavirus, and have been responsible for approximately 90 per cent of rotavirus disease in recent years in the US. The post-hoc analysis evaluated healthcare utilization data from rotavirus gastroenteritis caused by a fifth serotype, G9P1A.

Studies have shown that G9 strains (which include G9P1A and G9P2) appear to have changed in prevalence over time and are now considered to be one of the globally important strains. G9P1A is also recognized as one of the common circulating serotypes of rotavirus historically in the US.

"Because serotype distribution has been shown to vary between geographical settings and from one rotavirus season to another, it is important to help protect infants and children from many of the common circulating serotypes of rotavirus," said David Matson, M.D., Ph.D., Professor of Paediatrics and Director of the Graduate Program in Public Health at Eastern Virginia Medical School and Old Dominion University. "Merck's pentavalent rotavirus vaccine's prescribing information has now been updated to include post-hoc analysis data on another circulating rotavirus serotype of clinical and epidemiologic importance."

In REST, Rotateq demonstrated 98 per cent efficacy against severe cases of rotavirus gastroenteritis and 74 per cent of all rotavirus gastroenteritis cases caused by rotavirus serotypes G1, G2, G3 and G4 through the first rotavirus season post-vaccination (n=5673). Additionally, Rotateq reduced hospitalisations by 96 per cent (n=68,038) and reduced emergency department visits by 94 per cent (n=57,134) for rotavirus gastroenteritis caused by the G serotypes targeted by the vaccine (G1-G4), through two years following the third dose. Rotateq may not protect all vaccine recipients against rotavirus.

Rotavirus is a leading cause of severe acute gastroenteritis in infants and young children. It is highly common and contagious, infecting nearly all children by the age of five, many more than once, in both developed and developing countries. In the US, Rotateq is recommended by the US Centres for Disease Control and Prevention's Advisory Committee on Immunization Practices (ACIP) and the American Academy of Paediatrics (AAP).

Among children under five in the United States, it is estimated that 2.7 million episodes of rotavirus gastroenteritis occur each year, with an estimated 205,000 - 272,000 emergency room visits and up to 70,000 hospitalisations.

Rotateq should not be administered to infants with a demonstrated history of hypersensitivity to any component of the vaccine. No safety or efficacy data are available for the administration of Rotateq to infants who are potentially immunocompromised or to infants with a history of gastrointestinal disorders, the company informed.

More than 71,000 infants were evaluated in three phase III placebo-controlled clinical trials. Serious adverse events occurred in 2.4 per cent of recipients of Rotateq when compared to 2.6 per cent of placebo recipients within the 42-day period of a dose of Rotateq. Hematochezia, reported as a serious adverse event for Rotateq compared to placebo, was less than 0.1 per cent vs. less than 0.1 per cent. The most frequently reported serious adverse events for Rotateq compared to placebo were bronchiolitis, gastroenteritis, pneumonia, fever, and urinary tract infection.

In a subset of more than 11,000 infants in these trials, the presence of adverse events was reported for 42 days after each dose. Fever was observed at similar rates in vaccine and placebo recipients (42.6 per cent vs. 42.8 per cent). Adverse events that occurred at a statistically higher incidence within 42 days of any dose among recipients of Rotateq as compared with placebo recipients were diarrhoea (24.1 per cent vs. 21.3 per cent), vomiting (15.2 per cent vs. 13.6 per cent), otitis media (14.5 per cent vs. 13.0 per cent), nasopharyngitis (6.9 per cent vs. 5.8 per cent), and bronchospasm (1.1 per cent vs. 0.7 per cent).

In post-marketing experience, cases of intussusception have been reported in temporal association with Rotateq.

In the United States, the first dose of Rotateq should be administered between six and 12 weeks of age, with the subsequent doses administered at four- to 10-week intervals. The third dose should not be given after 32 weeks of age. The safety and efficacy of Rotateq have not been established in infants less than six weeks of age or greater than 32 weeks of age.

Rotateq was approved by the FDA on Feb. 3, 2006. Through Sept. 30, 2007, Merck has distributed more than nine million doses of Rotateq and Rotateq has been approved in 69 countries around the world.

Rotateq is a live, oral pentavalent vaccine that contains five live reassortant rotaviruses (G1, G2, G3, G4, and P1A).

Merck & Co., Inc. is a global research-driven pharmaceutical company dedicated to putting patients first. Established in 1891, Merck discovers, develops, manufactures and markets vaccines and medicines to address unmet medical needs. The company devotes extensive efforts to increase access to medicines through far-reaching programs that not only donate Merck medicines but help deliver them to the people who need them. Merck also publishes unbiased health information as a not-for-profit service.