Varicella vaccine were vaccinated as children were still protected from varicella." However, since only one out of five Japanese children were vaccinated, the annual exposure of these vaccinees to children with natural chickenpox boosted the vaccinees' immune system. In the United States, where universal varicella vaccination has been practiced, the majority of children no longer receive exogenous (outside) boosting, thus, their cell-mediated immunity to VZV (varicella zoster virus) wanes—necessitating booster chickenpox vaccinations. As time goes on, boosters may be necessary. Persons exposed to the virus after vaccine tend to experience milder cases of chickenpox. Catching "wild" chickenpox as a child has been
Lyme disease and muscle and joint pains from treatment which may last for one or two days. In those who develop persistent symptoms, long-term antibiotic therapy has not been found to be useful. Lyme disease is the most common disease spread by ticks in the Northern Hemisphere. It is estimated to affect 300,000 people a year in the United States and 65,000 people a year in Europe. Infections are most common in the spring and early summer. Lyme disease was diagnosed as a separate condition for the first time in 1975 in Old Lyme, Connecticut. It was originally mistaken for juvenile rheumatoid