GENEVA (Reuters) - The World Health Organization (WHO) welcomed Moderna reporting on Monday that its experimental vaccine showed 94.5% efficacy but said that “many questions” remained and it was no time for complacency.Only very limited amounts of any vaccine will be available in the first half of 2021 for people other than priority health workers, WHO officials said. “While we continue to receive encouraging news about COVID-19 vaccines and remain cautiously optimistic about the potential for new tools to start to arrive in coming months, right now we are extremely concerned by the surge in cases we are seeing in some countries, particularly in Europe and the Americas,” WHO director-general Tedros Adhanom Ghebreyesus told a news briefing. It marked his return to the Geneva agency from quarantine after being exposed to coronavirus some 17 days ago. Tedros said he had no symptoms and had seen no need for a test. Moderna Inc’s experimental vaccine is 94.5% effective in preventing COVID-19 based on interim data from a late-stage trial, the company said on Monday, becoming the second U.S. drugmaker to report results that far exceed expectations.