April 4 (HealthDay News) -- The U.S. Food and Drug Administration has approved a second oral vaccine for the prevention of rotavirus, an infection that causes vomiting and diarrhea in infants and children.

The Rotarix vaccine is a liquid and given in a two-dose series to infants from 6 to 24 weeks of age.

Rotavirus causes an estimated 2.7 million cases of gastroenteritis in U.S. children each year -- and about 55,000 to 70,000 of those children require hospitalization. Between 20 and 60 deaths are attributed to the infection. Without vaccination, nearly every child in the United States would likely be infected at least once with rotavirus by age 5, the FDA said in its late-Thursday announcement.

There are many strains of rotavirus; the new vaccine protects against rotavirus gastroenteritis caused by the G1, G3, G4, and G9 strains, the agency said.

"This vaccine provides another option to combat and reduce a potentially severe illness that affects so many children," Dr. Jesse L. Goodman, director of FDA's Center for Biologics Evaluation and Research, said in a prepared statement released Thursday night.

In studies involving more than 24,000 infants, Rotarix was effective in preventing both severe and mild cases of gastroenteritis caused by rotavirus during the first two years of life. The most common adverse reactions reported during clinical trials were fussiness, irritability, cough, runny nose, fever, loss of appetite and vomiting, the FDA said.

Rotarix is manufactured by GlaxoSmithKline Biologicals, of Rixensart, Belgium.

In 1999, a different rotavirus vaccine from another manufacturer was voluntarily withdrawn from the U.S. market because of an association with an increased risk of intussusception, or intestinal folding, which can lead to potentially life-threatening intestinal blockage. Intussusception can occur in children who haven't been vaccinated, but to help ensure that Rotarix doesn't increase the risk of intussusception, GlaxoSmithKline Biologicals conducted a study of more than 63,000 infants.

That study found no increased risk of intussusception in children who received Rotarix (31,673 infants) compared to those who received a placebo (31,552 infants). Increased rates of convulsion and pneumonia-related deaths were observed in the Rotarix recipients in the intussusception study, but these events were not observed in other studies conducted by the manufacturer, the FDA said.

Although the FDA said it has concluded that the available data do not establish that these adverse events are related to the vaccine, the agency has asked GlaxoSmithKline Biologicals to conduct post-marketing safety studies involving more than 40,000 infants to provide additional safety information.

The new FDA approval coincided with the release of results from a clinical trial of a different oral rotavirus vaccine in Latin American infants.

That study found that two doses proved effective against severe rotavirus gastroenteritis for up to two years when given during the first two weeks of life.

The double-blind, placebo-controlled phase III study included 15,183 healthy infants from 10 countries. They were randomly assigned to receive two oral doses of either the RIX4414 vaccine or a placebo.

The children were monitored until they were 2 years old. During that time, 32 of the 7,205 (0.4 percent) of children in the vaccine group had severe rotavirus gastroenteritis, compared with 161 of 7,081 (2.3 percent) of those in the placebo group.

Vaccine effectiveness was 80.5 percent to 82.1 percent against the wild-type G1 rotavirus strain, 77.5 percent against pooled non-G1 strains, and 80.5 percent against pooled non-G1 P(8) strains. Vaccine efficacy for hospital admissions for rotavirus gastroenteritis was 83 percent and admission for diarrhea of any cause was 39.3 percent.

The findings were published in the April 5 issue of The Lancet.

"Inclusion of this vaccine in routine pediatric immunization schedules can be expected to greatly reduce the burden of rotavirus disease worldwide," concluded Prof. Miguel O'Ryan, of the Institute of Biomedical Sciences at the University of Chile, and colleagues.

An accompanying commentary was written by Prof. Keith Grimwood of the Queensland Paediatric Infectious Disease Laboratory at Royal Children's Hospital and University of Queensland in Brisbane, Australia.

The World Health Organization, he wrote, "is awaiting efficacy data (on the vaccine) from low-income countries of Africa and Asia, where much greater strain diversity exists and where 413,000 rotavirus deaths occur every year compared with 15,000 in Latin America and 200 in Europe."

SOURCE: U.S. Food and Drug Administration, news release, April 3, 2008; The Lancet, news release, April 4, 2008