An Irish woman now living in Philadelphia is suing a major drug company and a Catholic order claiming she was used as a guinea pig in a drug experiment while a baby in Ireland in 1960 and 1961.

She claims  that a major U.S, drug company GlaxoSmithKline used Irish babies in homes for single mothers run by Catholic orders to experiment with a four in one shot against childhood diseases. The shots were later found to be less effective than the standard treatment.

Mari Steed, (50), born to an umarried mother, was given up for adoption to a couple in the US shortly afterwards. She says she and others were used a guinea pigs for a vaccine trial.

"The trials involved incredibly poor judgment on the part of all involved. We were basically used as human guinea pigs,"  Steed told the Irish Independent.

"There are at least four of us who are aware we were part of the trials, but there are probably more out there who don't know what happened to them."

She was given the vaccine on at least four times at the Sacred Heart Convent, Bessborough, in Cork, also known as the Bessborough Mother and Baby Home.

She realized she had been a guinea pig after she discovered her medical records when tracking down her mother Josephine in the 1990s.

Josephine, her mother has confirmed no permission was sought for the trial. “They didn't ask me for my permission to give her that shot,” she said.

Steed is filing a class action suit in the US courts against the multinational drugs giant responsible for the medical tests but is also suing the Catholic convent who allowed them, an Irish Independent investigation reveals.

Ms Steed and three others who were also subjected to the trials are looking to separately sue the Catholic religious order that they claim facilitated the experiments in the early 1960s. They are seeking details on whether they were paid for allowing the babies to be used.

Steed was involved in the first trial, which happened between December 1960 and November 1961 on 58 children in five different children's homes.

These were  St Patrick's Mother and Baby Home, Dublin; the Bessborough Mother and Baby home in Cork; and St Peter's Mother and Baby Home, Castlepollard, Co Westmeath. Children from St Clare's Baby Home in Stamullen, Co Meath, and the Good Shepherd Mother and Baby Home in Dunboyne, Co Meath.

The trial sought to find out what would happen if four vaccines for diphtheria (a life-threatening disorder caused by a highly contagious bacterial infection), pertussis (whooping cough), tetanus and polio were combined in one overall injection, known as the four-in-one shot.

However, the four-in-one jab never went into production after it failed to improve the previous standard vaccine.

Ms Steed's mother, Josephine is adamant she never gave permission for such shots.

Susan Lohan of the Adoption Rights Alliance said Ms Steed and other victims had been treated like "second-class" citizens.

Both the Sacred Heart Order and the drug company refused to comment.