The most effective means of prevention is the varicella-zoster vaccine, which is nearly 100% effective in two doses after 12 months of age. The vaccine is recommended for children over the age of 12 months as before this time, babies have maternal antibodies that will interfere with the vaccine. By their first birthday these antibodies will have mostly been eliminated. This vaccine is publicly funded in Canada and children are eligible for two doses. People with certain medical conditions that put them at an increased risk for complications due to varicella are also eligible for the vaccination. The vaccine may cause some side effects such as mild soreness, redness itching or rash where the vaccine was administered and low-grade fever. Some children may experience a mild, non-contagious form of chicken pox one to two weeks after the vaccine.