(1) The Secretary may, on his or her own initiative and by notice in writing given to the holder of a licence, vary a manufacturing site authorisation in relation to the licence.
(2) A variation under subsection (1) takes effect:
(a) if the notice states that the variation is necessary to prevent imminent risk of death, serious illness or serious injury--on the day on which the notice is given to the holder; or
(b) in any other case--on the day specified in the notice (which must not be earlier than 28 days after the notice is given to the holder).