The swine flu pandemic has cost the health system at least €100m and has infected more than 120,000 people so far.

However, the real cost to the economy is likely to be significantly higher when absenteeism and other cost considerations are taken into account.

At a time when the government is continuing its attempts to cut costs in the health service, figures supplied by the HSE show that it has cost €88m just to purchase the two vaccines aimed at combating the disease, Pandemrix and Celvapan.

It has also spent €27m building up stocks of the antivirals, Tamiflu and Relenza, although these would have been purchased from around 2006 onwards as part of ongoing pandemic planning.

Meanwhile, GPs who last week began providing the vaccine to those deemed to be "at risk" from the disease, are being paid €10 for each dose of the vaccine they administer.

While it may be decided not to give a second dose to all patients, the HSE is planning to provide two doses of the vaccine to some 400,000 patients in 'at-risk' groups, at an estimated cost of up to €8m in payments to GPs.

A total of 28,251 "at risk" people received the vaccine at various HSE clinics around the country since the programme of vaccination began last Monday. This does not include those who received it from their local GP, meaning the actual figure is likely to be significantly higher.

The Department of Health estimates that it could take six to eight months to vaccinate the entire population, as supplies of vaccines are limited.

But David Hughes, deputy general secretary of the Irish Nurses Organisation, claimed the HSE's plans to extend the vaccination programme to the wider population could face significant problems due to restrictions on funding.

He said that under the current programme focusing on "at risk" groups, such as those with chronic heart and lung conditions and women more than 14 weeks' pregnant, the HSE took nurses out of hospitals and other areas of the health service without replacing them.

"Part of the problem is that they're trying to do it without it costing anything," he said. "But this is going to become a major problem. They are currently relying on releasing nurses from places that they can't be released from.

"If they attempt to vaccinate the entire population they will need mass vaccination clinics, and to pay to replace the nurses involved in this."

Some 30,000 people contracted the swine flu virus in the Republic last week alone.