SNOHOMISH COUNTY — Health officials are hoping to boost local residents’ immunity to the H1N1 virus to prevent any possible “third wave” of illness.

“A ‘third wave’ of H1N1 illness is a real concern — unless half the population has immunity to the virus,” said Dr. Gary Goldbaum, health officer and director of the Snohomish Health District. “People develop immunity through vaccination or through illness. We estimate that between 30 percent and 40 percent of our community has some immunity to H1N1, but we need to boost that to 50 percent to stop the virus in its tracks, preventing a third round of illness in Snohomish County.”

The H1N1 (swine flu) initially began appearing in Snohomish County in spring 2009 before the vaccine was available. A second wave of H1N1 illness fell upon the region in fall 2009.

H1N1 vaccine began to trickle through to healthcare providers during that time so that the most vulnerable residents could be immunized.

Supply eventually caught up to demand, and immunization requirements were lifted in December, health officials said in a Jan. 11 release.

Snohomish County medical providers and pharmacies received approximately 200,000 doses of H1N1 vaccine between mid-September and mid-December.

As of mid-November, an estimated 47 million Americans have had the 2009 H1N1 influenza, with it accounting for 9,820 deaths, according to the release.

Immunization doses are available through retail chains and Snohomish County Health District.

For more information on H1N1, visit www.snocoflu.com.