Rotateq, the vaccine against rotavirus, has reduced the number of illnesses by at least two-thirds in its second year of use, according to a report released by the US Centers for Disease Control and Prevention and Quest Diagnostics.

Rotateq is usually given in three doses over the course of six months, being Merck’s second best selling vaccine last year with revenue of $525 million. The vaccine was approved in 2006 and it had a good secondary effect: it has severely slowed down the virus’ spread to non-immunized children in the U.S.

“We're a little surprised by the degree of impact given the coverage we've achieved,” said Jane Seward of the federal Centers for Disease Control and Prevention reporting the findings at the Interscience Conference on Antimicrobial Agents and Chemotherapy conference in Washington.

Before the vaccine, more than 200,000 children in the US were taken to emergency rooms and more than 55,000 needed hospitalization annually with rotavirus, mostly from January through May. Worldwide, the virus kills 1,600 young children each day.

Since Rotateq hit the market in 2006, hospital visits and stays due to the virus have dropped 80 percent to 100 percent, according to studies conducted by the CDC and several other groups.

Furthermore, a study conducted by Merck found a 100 percent drop in hospitalizations and ER visits during the 2007 and 2008 rotavirus seasons compared to previous ones. The results were based on a review of health insurance claims for about 61,000 infants and diagnosis by doctors in routine clinical practice.

"Rotateq provided 100 percent protection against hospital and emergency department visits when administered during routine public health practice," Merck's Christopher Mast told a news conference.

This does no meant children don’t become ill with diarrhea. They do, but they simply were not being made sick by the most dangerous strains of rotavirus targeted by the vaccine, Merck added.

And things are expected to get better as a second rotavirus vaccine was approved in April this year - GlaxoSmithKline PLC’s Rotarix. The vaccine is given in a two-dose series to infants from 6 to 24 weeks of age and protects them against rotavirus gastroenteritis caused by G1, G3, G4 and G9 strains of rotavirus.

Due to the vaccines’ effectiveness, the World Health organization is working to make them more available in developing countries where the rate of rotavirus infection is higher.

At the same conference, scientists reported that a new version of Wyeth’s Prevnar vaccine appears to better protect kids against germs that cause pneumonia, meningitis and ear infection, but whether it makes it onto the market before dangerous strains become a big problem remains to be seen. The vaccine came on the market in 2000 and is advised for children under age 2. It protects against the seven strains of Strep bacteria that were causing the most serious infections at the time. Since then, new strains have become more of a threat and increasingly are resistant to common antibiotics.