Rotavirus infection - the most common cause of diarrhea and vomiting in young children - has essentially disappeared from the United States since the introduction of an oral vaccination program in 2006.
"This is a disease that once plagued every emergency department and every hospital and it's now virtually gone," Daniel Payne of the U.S. Centers for Disease Control and Prevention told the Canadian Immunization Conference in Quebec City. "The case numbers are so low that the 2010 rotavirus season doesn't exist."
The vaccine is also pain-free, a liquid formulation squirted into the mouth of babies and requiring no needle.
Prior to vaccination, rotavirus killed about 21 children annually in the United States, and led to 57,000 hospitalizations and 107,000 ER visits, Dr. Payne said. Now, more than 80 per cent of children are immunized, and those numbers have fallen between 92 and 96 per cent.
Dr. Payne said one of the most surprising aspects of the U.S. vaccination program is that rotavirus-related illness has also fallen dramatically in older children who are not vaccinated, due to a phenomenon called herd immunity.
The success of the U.S. program increases pressure on Canadian provinces and territories to fund the rotavirus vaccine.
"Universal rotavirus immunization would be a really good thing," said Nicole Le Saux, an infection control physician at the Children's Hospital of Eastern Ontario in Ottawa. "The U.S. data are pretty convincing."
She said vaccination would not mean that diarrhea and vomiting in children will disappear, but the incidence and severity of the cases would be reduced markedly. Canadian research shows that rotavirus accounts for about 55 per cent of cases of diarrhea requiring emergency room treatment and about 72 per cent of cases requiring hospitalization. Rotavirus is dangerous largely because it leads to dehydration, which can, in some cases, lead to blood poisoning, seizures, life-threatening drops in blood pressure and even death.
"This is not always a simple gastro, it's a systemic disease," Dr. Le Saux said.
Canada's National Advisory Committee on Immunization recommends that all babies be vaccinated against rotavirus. It is not recommended for children after age three.
The Canadian Pediatric Society, for its part, has called on government to fund a universal vaccination program.
There are two rotavirus oral vaccines available in Canada: RotaTeq, a product of Merck Frosst Canada Ltd., requires three doses, and Rotarix from GlaxoSmithKline Inc., two doses. The total cost for either option is about $165.
No province or territory currently funds the rotavirus vaccine, though Prince Edward Island has pledged to do so.
The rotavirus vaccine has a rocky history. A vaccine called RotaShield was first sold in the United States in the late 1990s, but was pulled from the market in 1999 after it was linked to an increase in intussusception, a rare, life-threatening blockage of the intestine. That vaccine never made it to the Canadian market.
Because of safety fears, the clinical trials for the new vaccines were among the largest in history and there has been on-going safety monitoring.
"We are not seeing any elevated risk of intussusception in the U.S.," said Dr. Payne of the CDC.
In March of this year, however, use of the rotavirus vaccine was suspended briefly after traces of porcine circovirus (a swine disease) were detected in the vaccine. FDA investigators found that the virus was introduced through an additive but did not pose a risk to humans.
According to NACI, if all babies were vaccinated against rotavirus, about 33,000 physician visits would be avoided annually in Canada, as would be 15,000 emergency department visits and up to 5,000 hospitalizations. About two children die of rotavirus each year in Canada.
Data presented at the immunization conference also showed that about two-thirds of children hospitalized for treatment of symptoms of rotavirus are otherwise healthy, while one-third have underlying conditions that make them more susceptible.
Conference delegates also heard that rotavirus is the most common hospital-acquired infection in children.
André Picard