All children should receive two shots of the chickenpox vaccine, to ensure they are protected from the illness for a lifetime, Canada's pediatricians recommend in a new position statement.

Since 1999, the Canadian Paediatric Society has recommended that all young children be vaccinated at least once against chickenpox. Most provinces and territories have routine immunization programs in place for varicella, the clinical name for chickenpox.

Most kids get their first dose between 12 and 18 months of age.

Before a vaccine was available, there were about 5,000 chickenpox-related hospitalizations a year in Canada. But surveillance programs show that the number of hospitalizations for kids has decreased by up to 84 per cent in some provinces since the vaccine was introduced.

Now, new evidence suggests that two shots offer better lifelong protection against the illness, the CPS said in its position statement Tuesday. So the pediatricians recommend kids get a booster dose when they are between 4 and 6 years old.

Teens who have never had chickenpox should also get two shots, at least four weeks apart, the CPS recommends.

They say there's evidence that without that second vaccine dose, some children will lose immunity as they get older, making them susceptible to the illness as adults -- a time when chickenpox can be more serious.

"Adults who get chickenpox have more serious illness, are more likely to get pneumonia and to be admitted to hospital. They also have a higher death rate from the disease," explained statement author Dr. Marina Salvadori, in a news release.

No vaccine offers 100 per cent protection, but the CPS says two doses should improve immune response in those who get the vaccine.

Chickenpox is marked by a whole body rash of red spots that sometimes develop into fluid-filled blisters. The illness usually also brings fever, headache, a dry cough and fatigue.

Chickenpox usually develops two to three weeks after either physical contact with an infected person, or by breathing nthe virus. The illness then becomes most contagious about 24 hours before the rash appears, making it easy for infected people to spread the virus without realizing it.

Those who have actually become ill with chickenpox won't need the vaccine, though if they do get a dose, it's unlikely to cause any harm.

The statement puts the CPS in step with Canada's National Advisory Committee on Immunization, which already recommends a two-dose schedule for chickenpox, and has for a year.

The American Academy of Pediatrics has recommended two immunizations since 2007.

CPS also wants to see public funding for the chickenpox booster vaccine. Some provinces, such as Ontario, pay for the second dose, but not all provinces do. The position statement is urging all provinces and territories to cover both shots.

In statements made to The Canadian Press, Salvadori explained that one of the reasons the CPS issued this position statement is to put pressure on provinces to publicly fund it.

"What we're really hoping is the provinces all pick this up, and it becomes introduced in the next year or two in all Canadian provinces for all Canadian children," she said.

Certain people should not get the chickenpox vaccine, including:

• people who have a prior history of severe allergic reaction to the vaccine, or other components of the vaccine
• people with weak immune systems, unless under the supervision of a specialist in infectious diseases
• pregnant women or those who are trying to get pregnant
• babies less than one year old