Varicella zoster virus countries. Varicella vaccination has raised concerns in some that the immunity induced by the vaccine may not be lifelong, possibly leaving adults vulnerable to more severe disease as the immunity from their childhood immunization wanes. Vaccine coverage in the United States in the population recommended for vaccination is approaching 90%, with concomitant reductions in the incidence of varicella cases and hospitalizations and deaths due to VZV. So far, clinical data has proved that the vaccine is effective for over 10 years in preventing varicella infection in healthy individuals and when breakthrough infections do occur, illness is typically mild. In 2007,
Lyme disease small rodents—the primary reservoirs for Lyme disease. As a consequence of increased human contact with host and vector, the likelihood of transmission of the disease has greatly increased. Researchers are investigating possible links between global warming and the spread of vector-borne diseases, including Lyme disease. The term "chronic Lyme disease" is controversial and not recognized in the medical literature, and most medical authorities advise against long-term antibiotic treatment for Lyme disease. Studies have shown that most people diagnosed with "chronic Lyme disease" either have no objective evidence of previous or current infection with "B. burgdorferi" or are people who should