Spring is coming and with it the threat of Lyme disease. Fortunately, this is the second year adults at high risk of contracting the illness can at least be partially shielded from it. Many already are. More than a million doses of LYMErix have been dispensed since the FDA approved the vaccine in December 1998. Some questions regarding long-term safety and efficacy remain, but studies continue to support its use, and this year or next will likely see LYMErix licensed for children under fifteen.

In clinical trials, LYMErix, the only FDA-approved Lyme disease vaccination, was 78 percent effective in preventing typical Lyme disease and 100 percent effective against asymptomatic infections after three doses. Asymptomatic Lyme disease occurs without the characteristic red bulls-eye rash, making these infections harder to diagnose and treat.

The most common side effect of the vaccine is soreness around the injection site; flu-like symptoms occur less frequently. The vaccine is administered in three doses: an initial shot, a second after one month, and a final shot at one year. To ensure maximum defense, it’s important you receive all three doses. Most insurance companies now reimburse the vaccination cost.

Starting the inoculation process in mid- to late winter will guarantee some protection by spring and moderate protection by the summer. Researchers are still unsure how long LYMErix’s defense lasts, so they are evaluating the possible need for boosters. Two prospective trials found fourth and fifth doses did bolster vaccine effectiveness after two years without causing additional side effects.

Who Should Get the Vaccine

Currently, the Centers for Disease Control and Prevention (CDC) recommends that adults living or working in tick-infested areas who spend a lot of time outdoors — i.e., for work, exercise, recreation, or property maintenance — should consider getting vaccinated. It’s unclear whether those who aren’t outdoors much get any more benefit from the vaccine than they would from simply taking protective measures during exposure. Prior infection may not confer immunity, so those at risk who already have had Lyme disease may want to consider vaccination.

At this time, the vaccine is not approved for children under fifteen. However, a preliminary study has found the vaccine safe for them; and results from a larger study, involving 4,000 children, currently are being analyzed. LYMErix is not recommended for adults over seventy and people with a history of Lyme-related arthritis and neurologic conditions. It is given to pregnant women only if clearly needed.

Even if you fit the patient guidelines, a CDC study determined the vaccine is cost effective only for people living in high-risk areas or engaged in high-risk activities. Areas of highest Lyme disease risk in the United States are concentrated in New England, the Mid-Atlantic, and the upper Midwest. Even then, risk varies among towns and counties. So contact your county health department for information on Lyme disease prevalence your neighborhood. Ticks thrive in brushy, wooded, and overgrown areas. Activities placing people in these high-risk habitats include gardening, yard work, hiking, camping, and walking pets.

Tick Alert for Easterners

Researchers at the Institute of Ecosystem Studies in Millbrook, NewYork, have discovered that bumper acorn crops in eastern U.S. forests have a synergistic effect on mouse and deer tick populations, triggering explosive increases in tick density. The white-footed mouse, the primary reservoir of the bacterium that causes Lyme disease, is an important host of the second, larval stage of the deer tick. Acorns attract these mice and enhance their survival.

An acorn bonanza also attracts large numbers of white-tailed deer, the feeding and mating grounds of adult deer ticks. Female ticks drop off the deer in late winter to lay their eggs in the leaf litter, concentrating the tick eggs in oak stands during years of acorn abundance. In the spring the newly hatched eggs, or larvae, easily find their mice hosts and begin to collect the Lyme disease bacterium.

The risk of a human contracting Lyme disease appears highest the following spring, two years after a large acorn crop, when the numerous young ticks — now nymphs — go in search of larger hosts. Nymph tick densities on study plots simulating a large acorn year were eight times higher than normal.

Oaks produce mass acorn crops once every three to five years. And 1998 was just such a year in many eastern forests. This means the tick forecast for spring 2000 is grim, perhaps making this study the shot-in-the arm people at high risk of Lyme disease need to begin thinking about prevention.

Protect Yourself

Vaccination is no substitute for personal preventive measures. LYMErix is not 100 percent effective and is not effective against other deer tick-borne diseases like ehrlichiosis and babesiosis. If you are in tick-infested areas, the CDC recommends these precautions:

• Wear a long-sleeved shirt, long pants, and high socks with pant
  cuffs tucked into the socks. Light-colored clothing makes ticks easier to find.
• Walk in the center of hiking trails to avoid brushing up against vegetation.
• Use insect repellents containing at least 20-30 percent DEET. Spray clothes
  sparingly, especially children’s, and avoid direct contact with skin.
• Check for ticks after spending time outdoors. Prompt removal of ticks, 
  even after they have attached, can drastically reduce the chance of transmission.

Reprinted with permission from March, 2000 issue of the Harvard Women’s Health Watch, © 2000, Presidents and Fellows of Harvard College.

Originally published in the 2000 Spring issue of The CampLine.