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Experimental Dual Childhood Vaccine Disappoints

But finding doesn't apply to combination shots now in use, experts say

TUESDAY, April 12, 2005 (HealthDay News) -- An experimental combination childhood vaccine created to protect against both pneumonia and meningitis provided less protection than separate vaccines for the diseases, a new British study finds.

The combination vaccine was in the early stage of development, and was designed to protect against one form of pneumococcal infection and one form of meningitis. But the study found that children given the combined vaccine developed less of an immune response to meningitis than the standard separate vaccine.

The study included 240 healthy infants aged 7 to 11 weeks old when the trial began. Half were given the experimental vaccine three times -- at 2, 3 and 4 months of age, while half received the two separate vaccines now in common use on the same schedule. All the children also received the routine shots recommended for their age group.

Tests of their immune system response one month after the last shots were given found less protection against meningitis in the children who got the combination vaccine. Those children also had a reduced response to two of the other vaccines they were given.

The findings appear in the April 13 issue of the Journal of the American Medical Association.

The study does not apply to any of the combination vaccines now in use, said study author Dr. Jim P. Buttery, research director of the University of Melbourne Murdoch Children's Research Institute. He was at Oxford University when the study was conductd.

But it "underlines the importance of not only testing all the components of the combination vaccines but also that of any other vaccines given at the same time, even though they are not given in the same injection," Buttery said.

With American children now getting up to 20 vaccines, there has been a concerted drive to minimize the number of jabs they get by developing vaccine combinations. Perhaps the best known is the MMR -- measles, mumps and rubella -- vaccine. But a number of others also are being used, including one that provides protection against seven forms of pneumonia.

"We in public health have to proceed very cautiously and test all combinations carefully," said Dr. William Schaffner, chairman of the department of preventive medicine at Vanderbilt University and a member of the advisory group of the National Network for Immunization Information, a nonprofit organization.

The British trial shows that such caution is being practiced, Schaffner said, since a paper on the experimental vaccine is being reported in a publication aimed primarily at practicing physicians.

"Obviously, with our capacity to prevent more and more illnesses, the use of combination vaccines has been a high priority," Schaffner said. "But as we have learned, making a combination vaccine is more than just pouring the contents of one test tube into another test tube. Each combination vaccine must be tested, and then we have to make sure the combination vaccine does not interfere with other vaccines that are administered concurrently."

The report is an example of how well the effects of combination vaccines are being assessed, Schaffner added. "I have complete assurance that the vaccines that are being administered on a combination basis and concurrently have been tested very thoroughly and vetted by appropriate authorities," he said.

It's not clear whether the reduced immune response produced by the test vaccine was great enough to be clinically important, Buttery said. What it does show is that "if we want to use established licensed vaccines together that have not been tested before being given at the same time, similar studies may be warranted," he said.

More information

For more on vaccines, visit the National Network for Immunization Information.

SOURCES: Jim P. Buttery, M.D., research director, University of Melbourne, Australia, Murdoch Children's Research Institute; William Schaffner, M.D., chairman, department of preventive medicine, Vanderbilt University, Nashville, Tenn.; April 13, 2005, Journal of the American Medical Association
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