Prisoners in Irish jails will be among the first to be vaccinated against the swine flu virus, according to the HSE.

The vaccine against human swine flu arrived in the country last week and vaccinations are due to begin next month. Priority will be given to healthcare workers, then groups that are considered "vulnerable" will be given precedence.

"Health workers, such as doctors and nurses, will be given priority. After that, people with high-priority background such as the very vulnerable, like the elderly, the very young and pregnant women will be next. If someone incarcerated is deemed to be at risk by a medical clinician, they will be given priority. If they're in a high-priority group, it makes no difference whether they are inside or outside, they need to be vaccinated," said a spokesman for the HSE.

It is understood that because a proportion of the prison population have underlying heath problems, due in some cases to drug-addiction problems, the vaccine will be rolled out at prisons to prevent the spread of H1N1 flu. A source said that because prisoners live in such close proximity, a swine flu outbreak could put the Irish Prison Service (IPS) under severe pressure and healthcare workers at Irish jails would be unable to cope with a high volume of inmates struck down with the virus.

Some 7.7 million doses of the vaccine arrived last week. Dr Tony Holohan, chief medical officer at the Department of Health, has said the vaccine will be offered to the entire population, except for those under six months of age. It cost about €80m to purchase the swine flu vaccines. Even people who already have had swine flu will be offered the vaccine when a mass vaccination programme begins.