Reuters quoted a senior World Health Organization (WHO) official, as saying, on Monday. Addressing WHO's annual ministerial assembly, Bruce Aylward said that the interim results announced earlier in the day from Pfizer Inc's phase-three vaccine trials were "very positive"."The ACT Accelerator programme, which is an alliance between the World Health Organization, countries including France and organizations such as the World Bank, aims to fundamentally change the direction of the pandemic by March as more tests, treatments and vaccines become available," the WHO senior advisor said.Pfizer early trials show vaccine 90% effectiveEarlier today, American pharmaceutical Pfizer and its German partner BioNTech announced their Covid-19 vaccine.