Rotavirus vaccines reduce hospitalizations in kids

The introduction of the first rotavirus vaccine in the United States in 2006 led to sharp reductions in hospitalizations for gastroenteritis, an inflammation of the stomach and intestines that is marked by diarrhea and dehydration, researchers reported Wednesday. Rotavirus is one of the leading causes of gastroenteritis and was thought to be the cause of an estimated 55,000 to 70,000 hospitalizations in the United States each year before the introduction of the vaccine, Rotateq, in 2006 and the introduction of a second vaccine, Rotarix, two years later.

Epidemiologist Aaron T. Curns of the Centers for Disease Control and Prevention and his colleagues studied hospitalizations for gastroenteritis in 18 states accounting for almost 50% of the U.S. population. They compared rates for children hospitalized from 2000 to 2006 to those in the following two years. The team reported online in the Journal of Infectious Diseases that hospitalization rates for acute gastroenteritis dropped by 16% in 2007 and by 45% in 2008 compared with the earlier period. They estimated that about 55,000 hospitalizations were prevented during 2008 by the vaccinations, suggesting that the vaccine was highly effective at preventing most rotavirus cases.

The vaccines have been in the news recently because researchers have detected trace contamination of them by a pig virus that does not infect humans and that apparently causes no illness. In March, the Food and Drug Administration cautioned doctors against using the Rotarix vaccine because of the contamination. An FDA advisory panel earlier this month, however, said that both vaccines appeared safe and physicians should feel free to use them. The FDA has not yet issued a formal recommendation.

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Diabetes Drug Makes Vaccines Work Better

The diabetes drug metformin may make vaccines work better, exciting new studies suggest.

"These findings were unanticipated, but are potentially extremely important and could revolutionize current strategies for both therapeutic and [preventive] vaccines," University of Pennsylvania researcher Yongwon Choi, PhD, says in a news release.

Choi's team wasn't initially interested in diabetes drugs -- and wasn't trying to improve immunizations.

The scientists were trying to figure out how the immune system remembers disease-causing agents so that it can mount a rapid immune response the next time it sees that agent.

This so-called immune memory depends on cells called memory T cells that lurk in the body, becoming active only in the presence of the pathogen they're programmed to recognize.

During an infection -- or after an immunization -- the body mounts a massive T-cell response to fight off the invasion. These T cells go away after the threat is neutralized, but a few of them survive to become memory T cells. How this happens has been a mystery.

Choi's team found that memory T cells survive by switching their fuel supply. Instead of burning glucose, as most cells do, they start burning fat. The researchers bred a strain of mice that lacked the ability to switch fuel sources, and these mice could no longer make memory T cells.

One of metformin's effects is to help cells burn fat. When Choi and colleagues gave metformin to the specially bred mice, the drug restored the animals' ability to make memory T cells.

This led the researchers to wonder what would happen if they gave metformin to normal mice. So they injected the mice with doses of an experimental cancer vaccine that, under normal circumstances, does not protect the animals. But in mice given metformin, the vaccine was vastly more effective at preventing cancer.

"The finding was very unexpected. We were lucky," Choi tells WebMD.

The serendipity may pay off in big ways.

"The findings do not mean that if you take metformin you automatically have better memory responses," Choi says. "But this widely used drug might enhance vaccination programs. If we combine our finding with those strategies, we may be able to improve vaccine efficacy."

Source : www.webmd.com

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Regular flu vaccine little help against new strain

The seasonal flu vaccine provides virtually no protection against the new H1N1 influenza strain, federal health researchers confirmed on Thursday.

Their study using stored blood samples supports an intriguing theory that people over the age of 60 have some immunity to the new H1N1 strain, perhaps because it resembles an older version of seasonal flu.

The findings are important as U.S. and global health officials grapple with the question of whether to offer a vaccine against the new swine flu virus, which has infected more than 11,000 people globally and killed at least 85.

They also illustrate the need for a so-called universal influenza vaccine -- one that can protect people from a range of strains of the constantly changing virus.

"We would love to have an influenza vaccine that did not have to be reformulated each year," Dr. Anne Schuchat of the U.S. Centers for Disease Control and Prevention said at a news briefing.

The researchers at the CDC, Food and Drug Administration, National Institute of Allergy and Infectious Diseases, along with, universities and vaccine makers, looked at blood samples given after people were vaccinated for seasonal flu.

Seasonal flu vaccines carry an H1N1 component, an H3N2 strain and an influenza B strain. They tested these samples against both seasonal flu viruses and the new H1N1 strain.

Blood from children showed no immune system protection from the new strain, they wrote in the CDC's weekly report on death and disease.

PRE-EXISTING IMMUNITY

"Results among adults suggest that some degree of pre-existing immunity to the novel H1N1 strains exists, especially among adults aged over 60 years," the researchers added.

One possible explanation is that older adults were either infected with or vaccinated against a much older strain that more closely resembles the new H1N1 strain.

Schuchat said it is odd that genetic analysis shows the new swine flu virus is very different from any other H1N1 virus seen previously. There may be an aspect to flu viruses that the human immune system recognizes that does not show up in the genes, she said.

"We are wondering whether there were viruses around in the 1930s, 1940s, 1950s that were immunologically similar," she said.

The H1N1 family of flu viruses was first documented when it caused the 1918 influenza pandemic. H1N1 viruses have been circulating among humans and pigs on and off since then but with frequent mutations and shifts.

Because of these changes, the seasonal flu vaccine must be reformulated every year.

Schuchat said the tests done for the study cannot show whether the immunity seen in the blood samples was enough to protect people from infection with the new strain.

On Thursday the CDC reported 5,764 confirmed U.S. cases of the new flu and nine deaths. Schuchat said it is likely more than 100,000 people have been infected.

An unusually high proportion of those being infected and hospitalized with serious disease are young adults, teenagers and older children. Seasonal flu, in contrast, is usually far more severe in very young children, people over the age of 65 and people with chronic disease.

"We think this virus is initially amplifying among teenagers in schools and college students coming back from spring break and mixing," Schuchat said. It may move into other age groups later, she said.

Source : www.reuters.com

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