The announcement that a UK blood donor, who contributed a stabilising agent used in the manufacture of oral polio vaccine, has developed CJD will be a source of concern to parents.
Approximately 83,500 doses of the polio vaccine in question were distributed in the Republic between January 15th, 1998, and January 30th, 1999. Not all these vaccines would have been administered: there is a significant natural wastage of oral polio vaccine during its storage.
In addition, the Evans/ Medeva company was one of only two manufacturers of vaccine supplied here. Children given the SmithKline Beecham vaccine during the period under review are in no way affected.
For those children who received the Evans/Medeva vaccine during 1998 and early 1999, it is important to put the risk of developing new variant CJD in context.
First, the infected individual was not the only source of albumin, which is used as a stabilising agent in the vaccine manufacturing process. The person's blood was one of 22,353 blood donations used to make a pool. This in turn was combined with another pool to give a final dilution of one in 63,866.
Apart from the beneficial effects of dilution, the purification methods used in the manufacture of albumin are effective in eliminating the potential for infectivity. Recent studies of the various plasma fractions have shown no infectivity associated with albumin.
Prof Hall of the Virus Reference Laboratory in UCD told yesterday's press conference the risk of getting CJD from this batch of vaccine is zero. This is a significant statement from a leading authority on communicable diseases.
The Department of Health and Children has said the potential risk to recipients is essentially non-existent. "It is not possible in medicine to state that there is zero risk. However, in this situation, we are confident that this almost certainly the case," it said.
The National Disease Surveillance Centre has advised parents to continue with the normal vaccination programme. An uptake of less than 90 per cent over time would lead to the re-emergence of the wild or natural polio virus in the State and inevitably cause an outbreak of poliomyelitis and the re-establishment of the disease here. We have already observed this phenomenon in relation to measles: a low uptake of MMR vaccine saw a measles epidemic in the State this year.
At present, there is an average incidence of one case of polio in a recipient or contact of a recently vaccinated baby per two million doses of vaccine administered. It is vital to continue with a high uptake of oral polio vaccine if this low incidence of the disease is to be maintained.