The American Academy of Pediatrics (AAP) Committee on Infectious Diseases has issued recommendations for the prevention of Lyme disease. The recommendations appear in the January 2000 issue of Pediatrics.

[ corrected] Lyme disease, a disease transmitted by ticks carrying the spirochete Borrelia burgdorferi, is the most common vector-borne illness in the United States. The disease appears to be on the rise, with approximately 12,500 cases reported annually between 1993 and 1997. Ninety percent of cases originate in the northeastern and north-central United States. Lyme disease is carried by the black-legged tick, also known as the deer tick.

Persons most at risk for Lyme disease are those whose activities put them in wooded, brushy or overgrown grassy areas, where ticks are most likely to be found. The highest rates of infection are reported in persons between two and 15 years of age and 30 to 55 years of age.

Prevention

Persons can lessen their risk of Lyme disease by reducing their exposure to ticks. Insect repellents that contain n,n-diethyl-m-toluamide (DEET) are effective but must be reapplied every one to two hours. Persons should be instructed in methods of examining themselves for ticks after being in tick-infested areas. Ticks often attach to hairy areas of the body, especially the head and neck.

Studies have shown that transmission of B. burgdorferi usually requires ticks to be attached for at least 48 hours; therefore, ticks should be removed promptly. The tick should not be squeezed when removing. Tweezers should be used to grasp the tick as close to the skin as possible and removed by firmly pulling straight out without twisting.

Treatment of Tick Bites

The AAP reports that routine use of antimicrobial pro-phylaxis is not recommended because of the potential for adverse reactions and associated costs. In highly endemic areas, at most 20 to 30 percent of deer ticks are infected with B. burgdorferi. The risk of infection after a bite by a deer tick in an endemic area is about 1.4 percent. Most persons who become infected develop erythema migrans at the site of the bite, which is diagnostic of early Lyme disease. Children can be treated easily and effectively at this stage of disease, with little risk of long-term complications.

Because it is unlikely for there to be detectable antibodies at the time of a tick bite, such testing would likely be misleading. The AAP does not recommend serologic testing for Lyme disease at the time of a tick bite. Presence of antibodies at the time of a tick bite would likely represent a false-positive result or evidence of an earlier infection, says the AAP.

Vaccination

According to the AAP, the decision to recommend vaccination should be based on a person's risk of being bitten by ticks infected with B. burgdorferi. Factors that should affect the decision include the density of ticks in the area, the prevalence of B. burgdorferi infection among those ticks and individual behavior. State and local health departments can provide information on the risk of infection in specific areas.

The AAP reports the results of animal studies on vaccines against Lyme disease. It has been shown that purified recombinant proteins, especially of outer surface proteins (Osp) of B. burgdorferi, such as Osp A, B and C, induce protective responses. In particular, the recombinant OspA (rOspA) is highly effective against challenge strains that are homologous or closely related to the isolate of OspA. The rOspA vaccine seems to have a unique mode of action, although the exact mechanism by which the antibody works is unknown. Early clinical trials on humans demonstrated that rOspA was immunogenic and well-tolerated. The vaccines have been produced by two manufacturers and field tested in humans. Only one vaccine, LYMErix, is licensed at this time by the U.S. Food and Drug Administration (FDA). The vaccine is administered intramuscularly in three doses of 0.5 mL (30 μg); the second dose is given one month after the first, and the third dose is given 11 months later, one year after the first dose. Dosages should be timed so that the second and third doses are given several weeks before the start of Lyme disease season, which begins in April.

The AAP reports on the efficacy of the vaccine in a controlled trial of 10,936 subjects. In the year after the first two injections, the vaccine efficacy against Lyme disease was 49 percent. In the second year after the third injection, efficacy rose to 76 percent. According to the AAP, it is unknown whether the protective immunity will last more than a year beyond the third dose. The data suggest that boosters may be necessary to extend protection. Adverse reactions to the vaccine usually occurred within 48 hours of injection. The most common reaction was soreness at the injection site, reported by 24 percent of recipients. Systemic symptoms such as myalgias, achiness, fever and chills were reported by fewer than 3 percent of subjects. Such symptoms were usually mild to moderate in severity.

Recommendations

The AAP's recommendations are as follows:

• Attempts to minimize exposure to vector ticks in residential areas is encouraged. Heavily tick-infested areas should be avoided, if possible. If not possible, then personal protective measures (e.g., wearing specific types of clothing, use of repellents, frequent checks for ticks), and early detection and treatment of disease manifestations are encouraged.

• Routine use of antimicrobial agents to prevent Lyme disease after a deer tick bite, even in highly endemic areas, is not recommended. Serologic testing for Lyme disease at the time of a recognized tick bite is also not recommended.

• Use of Lyme disease vaccine is recommended in the following cases:

1. Administration of the vaccine should be considered for the following persons who are 15 years of age or older: those who spend time in geographic areas of high risk and whose activities result in frequent or prolonged exposure to vector ticks; and those who visit geographic areas of high risk during the peak Lyme disease transmission season and whose activities result in frequent or prolonged exposure to vector ticks.

2. The vaccine may be given to persons who reside, work or recreate in areas of high or moderate risk and whose activities result in some, but neither frequent nor prolonged, exposure to vector ticks. However, the benefits of vaccination for these persons compared with those of personal protective measures and early treatment of Lyme disease are unclear.

3. The vaccine is not recommended for the following: persons who reside, work or recreate in areas of high or moderate risk but who have minimal or no exposure to infected ticks; persons who reside, work and recreate in geographic areas of low or no risk; and children younger than 15 years until data about the safety and immunogenicity of the vaccine in this age group are available and the FDA has labeled the product for use in this age group.

4. Immunization should be considered for persons with a history of Lyme disease who are at continued high risk. However, persons with antibiotic-resistant Lyme arthritis should not be immunized because of the association between this condition and immune reactivity to OspA. Persons with chronic joint or neurologic illness related to Lyme disease, as well as those with second or third degree atrioventricular block, were excluded from the phase III safety and efficacy trial; thus, the safety and efficacy of Lyme disease vaccine for such persons is unknown.

5. The safety and efficacy of the simultaneous administration of rOspA vaccine with other vaccines have not been established. Administration of rOspA vaccine should not interfere with the administration of routinely recommended immunizations. If rOspA vaccine is to be given concurrently with other vaccines, each should be administered in a separate syringe at a separate site.

6. Data are lacking on the safety and efficacy of rOspA vaccines in persons with immunodeficiencies. General guidelines for administration of inactivated or subunit vaccines should be followed (see the current edition of Red Book).

7. Because the safety of rOspA vaccine administered during pregnancy has not been established, immunization of women known to be pregnant is not recommended. A vaccine pregnancy registry has been established by the manufacturer. In the event that a pregnant woman is immunized, health care professionals are encouraged to register this immunization by calling 800-366-8900, extension 5231.