SYDNEY — Singapore suspended quarantine-free travel and Australia renewed its vaccination push on Wednesday as surging cases of the Omicron coronavirus variant just days before Christmas forced authorities to impose new curbs and expedite booster shots.

Governments globally have tightened social mobility restrictions and made urgent pleas for citizens to vaccinate as Omicron emerges as the dominant strain of the virus, upending reopening plans that many hoped would herald the start of a post-pandemic era in 2022. 

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