The New Lyme Disease Vaccine--Lots of Caveats

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The long-awaited Lyme Disease vaccine is available. This might come as good news to people living in the Northeast, the Middle-Atlantic states, Michigan and Wisconsin where 90% of LD cases occur. But because of its many limitations, the vaccine has been met with a certain amount of wariness. "We're glad there is one [a vaccine]. This season it should cut down the new cases," said Tom Forschner, executive director of the Lyme Disease Foundation, a non-profit organization dedicated to research, education and advocacy for tick-borne disease. "But we're a tad cautious, hoping there will be no adverse side effects.

"The vaccine is not 100% effective against all the strains of the bacteria that cause tick-borne disease," continued Forschner, in a telephone interview. "And there are 200 different strains in U. S. alone. This vaccine won't work at all in Europe, and it won't protect against two strains--ehrlichiosis and babesiosis--which represent between 20% and 37% of all tick-borne diseases." The new vaccine is called LYMErix by its manufacturer, SmithKline Beecham Biologicals.

LD is an inflammatory infection caused by bacteria that reside in the gut of deer ticks. It is transferred from animals to humans when the tick sucks the blood of an infected white-footed mouse or white-tail deer and then sucks the blood of a human once it becomes imbedded in the skin. The infection produces flu-like symptoms, fever, musculoskeletal pain, headache, and swollen lymph nodes. If not treated promptly and properly, LD can affect several different organ systems with devastating results, such as facial paralysis, cardiac arrhythmia, depression, dementia, and memory problems. About six months after infection, approximately 60% of untreated people develop arthritis which in some cases will be resistant to treatment. About 90% of all LD cases are cured by prompt treatment with antibiotics. But a timely diagnosis is thwarted by the fact that only half of all people bitten by an infected tick will have the telltale red, swollen, circular rash which appears 3-30 days later. And the standard blood-antibody test will miss about 60% of all infected cases. Understandably, hopes are pinned on the LD vaccine.

A vaccination usually produces immunity by triggering the appropriate antibodies (infection-fighting proteins) in the bloodstream, but LYMErix works in an entirely different manner. Its action centers on the gut of the blood-sucking tick. When a tick sucks the blood of a vaccinated person, it ingests the antibodies triggered by the vaccine. The antibodies overpower the LD spirochetes, or bacteria, in the tick's intestine before the infection can take hold in the vaccinated person.

Though children are at the highest risk for LD, LYMErix was approved recently by the Food and Drug Administration only for people aged 15 to 70 years because the vaccine has been tested and proven safe and effective for this age group. The 11,000 participants all lived in endemic areas. Half received the LD vaccine in a series of three injection at 0, 1, and 12 months; half were given injections of an inactive substance (the placebo group). Neither the participants nor the investigators knew who was receiving the LD vaccine. After two injections, 22 people in the vaccinated group got LD, as compared with 43 people given placebo injections. After three injections, the efficacy rate rose to 76% (New England Journal of Medicine, 7/23/98). A diminished efficacy was observed in people over 65 years. The study only followed the participants for 20 months; therefore the vaccine's long-term safety and efficacy is unknown. For example, there is no information about the duration of the immunity conferred by the vaccine; most experts believe booster shots will be necessary, probably on a yearly basis.

The most alarming potential adverse reaction to this vaccine came from an animal study presented at last month's 12th International Conference on Lyme Disease and Other Spirochetal and Tick-Borne Disorders, sponsored by the LDF. Dr. Ronald Schell, of the University of Wisconsin School of Medicine in Madison, presented the results of his study of hamsters that suggest a connection between use of the LD vaccine and the induction of arthritis. Hamsters were chosen because of the similarities of the LD disease process in this species and in humans. Using the same type of newly approved vaccine which consists of recombinant-derived outer surface protein A, Dr. Schell found that "severe destructive arthritis" developed in vaccinated hamsters after they were infected with the live LD-causing bacteria. "Several studies laid the groundwork for these most recent findings," said Dr. Schell. Some conference attendees expressed reservations about Dr. Schell's findings because he used only culture-grown organisms in his study rather than LD-infected ticks and because hamster results may not directly apply to humans. Until more is known, some experts advise against use of the LD vaccine by people with arthritis.

In a telephone interview, Pierce Gardner, M.D., State University of New York at Stony Brook, Long Island, was asked who should have the LD vaccination series. "It's a tough question," he answered. "This is a vaccine that does some good, but it's expensive and it's not perfect." Suitable candidates are people living in counties where LD is endemic, according to Dr. Gardner, who believes that geography is even more important than having an outdoor occupation that puts you in contact with ticks. As for the possibility that the vaccine could trigger arthritis, Dr. Gardner said, "The [vaccine] data are reassuring for people who were infected with LD in the past, but nothing is known about the vaccine's effect on people with LD arthritis--the clinical trial eliminated from participation all people with arthritis."

Because the vaccine has its limitations and because ticks carry other diseases, doctors advise people to concentrate on prevention such as: wearing light-colored clothing to see the tick more readily; tucking your pant legs into each sock; wearing tightly woven clothes; sitting on a blanket, rather than directly on the grass; staying on the trail; doing a tick check of your kids, pets and yourself after spending time outdoors; and spraying clothes with products containing permethrin or pyrethrins, both naturally derived insecticides that kill ticks.

For More Information:
Call the LDF hotline at 1(800) 886-LYME and visit the Web site at lyme.org for information on prevention and treatment. Since many people have difficulty finding a physician who is knowledgeable about Lyme disease, the LDF will refer to physicians where possible in the U.S. and Europe. Referral requests should be in writing to the LDF, One Financial Plaza, 18th floor, Hartford, CT 06103.

For a summary of the presentations at last month's international conference on LD, visit the Web site of the only peer-reviewed on-line medical journal at www.medscape.com.

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