By Renju Jose SYDNEY (Reuters) – Australia said on Thursday it would expand the rollout of the fourth dose of COVID-19 vaccines from next week as it battles a steady rise in hospital admissions fuelled by the highly transmissible new Omicron subvariants, BA.4 and BA.5. The new subvariants have now become the dominant coronavirus strains in several countries, with pandemic experts warning they could lead to more hospitalisations and deaths because they spread more quickly than other coronavirus variants. New South Wales, Australia’s most populous state, warned it was experiencing a fresh wave o…