Pregnant Irish women are to be offered a form of swine flu vaccine which the World Health Organisation says is not "the preferred option" from a safety point of view.

A spokeswoman for the HSE confirmed that the H1N1 vaccine Pandemrix, which contains a chemical called an 'adjuvant', will routinely be offered to expectant mothers here. This is despite the fact that the other vaccine which the HSE has in stock, known as Celvapan, does not contain the chemical.

According to a report from the WHO's own advisory group on immunisation produced last July, inactivated "nonadjuvanted vaccines", similar to most seasonal flu vaccines, are the "preferred option" when vaccinating pregnant women. This is due to the "extensive safety data on their use in pregnant women", the report states.

"If such a product is not available, pregnant women should be vaccinated with another pandemic influenza vaccine available at that time," it states.

The HSE recently ann­ounced details of its plans to vaccinate around 410,000 "at risk patients" in the coming weeks, including women who are 14 weeks pregnant or more. Its spokeswoman said around 55% of its vaccine supplies are Pandemrix, which is manufactured by GlaxoSmithKline, and the remainder are Celvapan, produced by Baxter healthcare.

She said both vaccines had been licensed by the European Medicines Agency and the Irish Medicines Board for use in pregnant women in the second and third trimester. As a result, she did not anticipate that plans to provide Pandemrix to expectant mothers would change. She added that many other European countries had also licensed Pandemrix for use with pregnant women.

Health experts in Britain have warned that if infection rates increase as expected, then pregnant women are at high risk and should be prioritised for vaccination with whatever vaccine is available.

However, Mairéad Hilliard of the Irish Vaccine Informed Parents campaign group said she did not believe Pandemrix should be given to pregnant women.