Dr. Colm Henry:

It is not akin to a normal vaccination programme, which is predictably seasonal and we deal with a set type of mutations of a virus. In this case, we are dealing with a virus that we are still getting used to and it is getting used to us, and it mutates somewhat unpredictably. What we found is that many vaccines went beyond their expiry dates but what is probably more important is that they were no longer fit for purpose for the type of variants that were circulating. The updated guidance from the national immunisation advisory committee, NIAC, in November 2022, for example, pointed towards a new type of bivalent vaccine which would be more effective.