New York state declared a public health emergency Saturday, in the latest push against the influenza epidemic gripping the United States and threatening parts of Canada.

The executive order allows pharmacists to administer flu shots to individuals under age 18, clearing the way for vaccinations to children as young as six months old. The mayor of Boston issued a similar declaration earlier this week and urged the public to get vaccinated against the virus.

The moves come as U.S. health officials battle widespread flu outbreaks in 47 of 50 states that have killed at least 20 children. There is no running tally of adult deaths, but the U.S. Centers for Disease Control estimates that flu kills more than 20,000 Americans each season.

Canadian media quote health officials who say most of the nearly 4,000 flu cases identified in seven provinces last week occurred in long-term care facilities.

European authorities report flu-related fatalities from a separate viral strain in Norway, Poland and the Czech Republic.

On Friday, U.S. officials reported a study showing that Americans vaccinated for the prevalent H2N3 virus are 62 percent less likely to come down with flu that requires physician visits, than those who go without the vaccine.

Despite that data, the CDC also reported that nearly 65 percent of Americans had not received a flu immunization by the end of November 2012.