Varicella Vaccine

Varicella-zoster is the virus which causes chicken pox and is also responsible for shingles. Chicken pox is most commonly seen in children under 12 years of age and is not seen again after having occurred as immunity is developed after sickness. A publicly funded vaccine is available in Canada, and two doses provide nearly 100% immunity against the disease.

Chickenpox occurs differently in people, with most reporting flu-like symptoms such as fatigue, mild headache, fever, chills, muscle or joint aches and other cold-like symptoms a few days before the itchy, red rash that is signature of chicken pox appears. The rash appears anywhere on the body as raised blisters that are extremely itchy. Some will have only a few while others will be completely covered. The patient is most contagious two days before the rash appears, and the blisters dry up and form scabs in four to five days after appearing. This disease can lead to more severe illnesses in 5-10% of children such as pneumonia, flesh-eating disease or infections of other portions of the body. Chicken pox is most dangerous to infants and to people with lowered immune systems.

Chickenpox is extremely contagious and spreads very quickly from unimmunized person to person. The most common way of transmission is through the air when the infected person coughs or sneezes. It can also be spread through the blisters. This disease occurs anywhere in the world but is most commonly seen in developing countries where the vaccine is not common. Anyone who has not previously had chickenpox or is not vaccinated against it is at risk of contraction. The disease is far more severe in adults than children. Mothers with chickenpox can pass the disease onto their newborn baby after birth, and this can be life-threatening to the child.

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.