By the way, doctor: Is my Lyme disease vaccination still effective?

Q. I was vaccinated against Lyme disease in 2000. Do I still need to be careful about tick bites?

A. Yes, you still need to be cautious about deer ticks, which carry the Borrelia burgdorferi bacterium that causes Lyme disease. The vaccine (Lymerix) was effective in clinical trials and released in 1998. But it was discontinued in 2002 because of concerns about adverse effects, although there was no proof that it was dangerous. Studies have shown that one dose of Lymerix protected most vaccine recipients for up to a year and about 50% for two years. Beyond that, the data are unclear, so don't assume that your vaccination is still working.