A batch of BCG vaccine, which is used to prevent tuberculosis, has been withdrawn from use in the Republic because of concerns about its effectiveness.
The Irish Medicines Board took the precautionary measure earlier this week when it was informed by the vaccine manufacturer that tests had shown that the batch concerned was less potent than normal.
However, the Department of Health and Children has emphasised that there is no health threat to the 2,500 people who received vaccines from the batch, other than that they might not have received adequate immunity.
BCG provides protection against tuberculosis (TB) infection and is normally administered to children at birth in maternity hospitals. It is also given to contacts of people who develop TB and who do not have immunity against the disease.
The batch in question, No 761641, was made by Evans Vaccines in Britain last November. It is understood to have passed a regulatory test in February and was distributed in the Republic on March 20th.
At the end of May the manufacturers carried out additional quality-control testing on a sample from the batch which suggested a problem with its potency. The company made the results of further tests available last Monday.
The Department of Health contacted the health boards and established that 2,500 sub-potent doses had been given in 33 hospitals and clinics throughout the State.
Health boards will contact those who received BCG vaccines from the batch to attend a clinic to establish whether the vaccine was effective. If this test, which must be carried out three months after vaccination, is negative, people will be offered re-vaccination.
To ensure the potency of all BCG vaccines in use, other batches have been withdrawn for testing of their effectiveness.
Dr John Devlin, deputy chief medical officer of the Department, said the BCG vaccination programme would be deferred until alternative supplies of vaccine were made available.
He emphasised that the problem represented a potency rather than a safety issue.