National Institute of Health
September 1, 2006
Each year, hospital-acquired infections sicken 2,000,000 people, killing about 80,000 of them. These infections add nearly $5 billion a year to U.S. healthcare costs. Moreover, many kinds of bacteria have grown resistant to the antibiotics used to eliminate them. A simple treatment for hospital patients, nursing home residents, and others at risk for hospital acquired infections would yield major benefits.
Recently, scientists reported a successful test of a vaccine against one of the most common causes of hospital-acquired infections, Staphylococcus Aureus bacteria. The method for creating the vaccine also holds promise for vaccines that target other disease-causing organisms, including those that could be used in a terrorist attack. The new Staph vaccine is the latest product of research begun decades ago as scientists sought a vaccine to protect infants and young children against Haemophilus Influenzae type B (Hib). This often-fatal bacterial infection was the leading cause of meningitis among children under five in the U.S.
In 1983, John Robbins, M.D., and Rachel Schneerson, M.D., set up an NICHD laboratory to develop vaccines that were effective against bacteria. The two developed a vaccine to target the simple sugar molecule, or polysaccharide, on the surface of the bacteria that causes Hib. Polysaccharide vaccines were a major improvement on existing vaccines, which consisted of whole bacteria that had been killed or weakened and which could cause severe side effects. After testing the vaccine, the NICHD scientists found that it was safe and that it stimulated protective levels of antibody in adults and older children. Antibodies are molecules made by the immune system. Like tiny guided missiles, they zero in on a particular substance, tagging if for later destruction by the immune system. Scientists supported by NIAID did further testing and, with the added involvement of industry, three Hib polysaccharide vaccines were produced and licensed in 1985. But infants and very young children – those most at risk of Hib infection – could not be immunized with the first formulations of Hib vaccine because of their immature immune systems. To overcome this problem, Robbins and Schneerson modified the vaccine, creating what is known as a conjugate polysaccharide Hib vaccine. To make the vaccine, the researchers chemically attached, or conjugated, the sugar molecule to a protein molecule. The infants’ immune systems easily recognized the protein molecule, and, in the process, learned to recognize the sugar molecule as well. Before this vaccine, Hib infected about 20,000 U.S. children under age five each year, causing about 12,000 cases of meningitis and 1,000 deaths. The Hib vaccine is now routinely used to immunize infants and children in the U.S., Canada, Western Europe, and many other nations. As a result, meningitis caused by Hib has all but disappeared in these countries. In the U.S., universal childhood vaccination with Hib saves a total of $2.9 billion (medical and indirect costs) each year.
The trial with the new Staph vaccine was conducted in patients with kidney disease receiving dialysis treatment. These patients were chosen because they are at high risk of infection and are among the least likely to respond to immunization. The vaccine protected the patients for a short time against the two strains of S. Aureus that cause 85 percent of Staph infections. Booster shots will be tested to lengthen the period of immunity. More research will be directed to making the vaccine effective against other strains of staph. Similar vaccines against other hospital-acquired infections are now being designed.
National Institute of Health