GIARDINI NAXOS, SICILY, Italy, Apr 11, 2003 (United Press International via COMTEX) -- The first vaccine designed to protect children simultaneously against measles, mumps, rubella and chicken pox appears promising in preliminary studies, researchers reported Friday.

The vaccine, being developed by Merck Research Laboratories of West Point, Pa., is exciting doctors because they see the potential of increasing vaccine coverage for infections of varicella, the organism that causes chicken pox.

"This is first in the world vaccine aimed at these four major childhood diseases," said Dr. Jay Lieberman, a researcher at the UCLA Center for Vaccine Research in Torrance, Calif. "We think that if we can reduce the number of shots young children have to take to be protected against these diseases we have the potential to get our numbers up to around 90 percent vaccinated against chicken pox," he told United Press International.

Lieberman presented his findings at the annual meeting of the European Society for Pediatric Infectious Diseases.

Vaccination for varicella -- recommended for U.S. children under age 2 -- has a wide range of coverage state-to-state. About 70 percent of the U.S. childhood population is covered.

"The drive in this field is to combine vaccines," said Dr. Jodie McVernon of the Public Health Laboratory Service Communicable Disease Surveillance Center in London. "The more visits you make to the doctors, the worse your vaccine coverage is likely to be."

In his presentation, Lieberman, who also is associate professor of medicine at the University of California, Irvine, said his study compared the ability of vaccinated children to produce antibodies to the diseases in three different lots of the medication -- a step required by the U.S. Food and Drug Administration to show the vaccine can be manufactured consistently.

The vaccine was administered to about three-quarters of 3,928 healthy children ages 12-to-23 months. The other children were given one injection of the MMR-II (measles, mumps, rubella) vaccine, which has been given to children for decades. These children also received a second injection of Varivax -- a chicken pox vaccine. The shots generally were given in each arm.

Researchers looked at seroconversion -- how well antibodies to the diseases developed -- after the inoculations were performed. They found the results were similar for each vaccine lot and, in turn, were similar to seroconversion seen in children receiving the two approved vaccines.

Lieberman also reported:

--In measles, 97.6 percent of children receiving experimental ProQuad vaccine showed seroconversion, compared to 98.5 percent of those getting the two vaccines.

--In mumps, 96 percent receiving ProQuad showed seroconversion, vs. 97.9 percent of those receiving the two vaccines.

--In rubella, 98.8 percent getting ProQuad showed seroconversion, vs. 99.2 percent of those getting two vaccines.

--In varicella, 93.5 percent getting ProQuad and 95 percent getting Varivax showed seroconversion.

Lieberman said children receiving ProQuad appeared to suffer more fevers in the six weeks following the inoculations -- 39.1 percent vs. 33.1 percent -- but he said he did not think the figures were clinically relevant. However, he noted there was no difference between the group receiving ProQuad and those getting the two vaccines, in terms of developing worrisome, fever-related seizures.

Lieberman said he expects Merck likely will file with the FDA for approval of the vaccine "soon" but he said he was not aware of an exact timetable to do so.

"Doctors are excited about the idea that they can deliver this vaccine in one shot," Lieberman said. "That has the potential to enhance compliance especially against chicken pox at an early age."