The first H1N1 vaccinations of children with underlying health problems have begun in canton Solothurn in northwestern Switzerland.
Doctors injected the anti-flu vaccine Focetria on Saturday, as reported by Swiss public television.
"It is mainly children with serious heart defects, lung problems or patients with weakened immune systems that we have immunised in a first round," Paul W. Meirer, a doctor from a Solothurn children's practice, said.
By mid-November, all 26 Swiss cantons should be in possession of the vaccine, the Federal Health Office said, allowing a national voluntary immunisation programme to get underway. But a spokesman could not confirm whether vaccinations had already begun in other cantons.
Meanwhile swine flu continues to spread in the army. The Bure barracks in canton Jura became the fourth this week to be hit by an outbreak, with five confirmed cases by Friday.
The swine flu pandemic is expected to hit Switzerland in earnest in the coming days, with confirmed cases tripling last week to around 2,000.
swissinfo.ch and agencies