(C) 1995 The Washington Post (LEGI-SLATE Article No. 223239)

BOSTON, Feb. 22 -- Tackling a medical mystery of why many Romanian children developed polio after being vaccinated, researchers have found that injections given shortly after vaccination can increase the risk of contracting the disease.

The weakened strain of the live polio virus used in the oral vaccine can survive for a time in the intestinal tract, where it sometimes reverts to a more virulent, "wild-type" form of the virus capable of causing disease. But in the United States and most other developed countries, cases of paralytic polio associated with the vaccine are extremely rare.

In a study of Romanian children, investigators from the Centers for Disease Control and Prevention in Atlanta found that a single injection given within one month of the oral polio vaccine was administered raised the risk of polio to eight times higher than that of children who received no injections.

After between two and nine injections, the risk jumped 27-fold. And with 10 or more injections, the likelihood of developing polio was 182 times greater than expected, the researchers found.

"The risk of paralytic disease was strongly associated with injections given after the oral polio virus vaccine, but not with injections given before or at the same time as the vaccine," said the research team, led by Peter M. Strebel.

In an editorial in the Thursday issue of the New England Journal of Medicine, where the study appears, Peter F. Wright and David T. Karzon of Vanderbilt University in Nashville cautioned that the problem rarely appears in developed countries with sophisticated medical care and therefore "the data from Romania must not be allowed to detract from the impressive gains in the control of poliomyelitis being achieved with the widespread use" of the oral vaccine.

The problem emerged in Romania because, unlike in the United States and other developed countries, babies frequently receive antibiotics by injection instead of in liquid form.

The study was undertaken because of an unusual number of polio cases in newly vaccinated children in Romania. Initially, health officials had blamed local vaccine. But the additional cases continue to appear even after an imported vaccine was used.

Why injections should increase the risk of polio in newly vaccinated children remains a mystery. But the Strebel team speculated that when the muscle is injured during an injection, it may allow the polio virus from the vaccine to get into the nerve endings, where it can cause the disease.

courtesy of: The Rollin' Rat -- Post-Polio Syndrome