Doctors' surgeries in Guernsey and Alderney have received 7,000 doses of influenza vaccine to be dispensed.
Dr Stephen Bridgman, director of public health, said: "I strongly encourage people in the high-risk categories to receive the vaccination.
"It is a very cost-effective way of reducing the risk of preventable illness, hospital admission or even premature death."
This year the vaccine includes protection against H1N1 (swine flu).
HSSD's prescribing advisor Geraldine O'Riordan said although it was optional she recommended those in "at risk groups" got the jab.
That includes islanders aged 65 years and over, people with chronic health conditions and to anyone caring for the elderly in residential or nursing homes or in the community.
For the first time pregnant women are included in the programme, following a study in Australia and New Zealand, which found that they were at a higher risk of developing critical illness associated with H1N1 flu.
Miss O'Riordan said: "Patients who had a swine flu vaccination last year will still need this combined jab in the next few weeks to protect them against this winter's seasonal flu.
"I am delighted that the vaccine has arrived earlier than expected and I would urge all residents entitled to receive it to contact their surgery to make an appointment as soon as possible."
The Health Department said further deliveries were expected over the next couple of weeks and all residents who were entitled to receive the vaccination should contact their surgery to make an appointment.
Although the vaccine for those at high risk is provided freely, there is a charge for the doctor or nurse consultation.