Geneva, Nov 11 : WHO Director-General Tedros Adhanom Ghebreyesus has called for "fair allocation" of a Covid-19 vaccine after drugmakers Pfizer and BioNTech this week said that their vaccine candidate was found to be more than 90 per cent effective in preventing the disease in interim analysis of data. Addressing the member states at the 73rd World Health Assembly on Tuesday, the WHO chief said that the UN health agency welcomes Pfizer's "promising news" and expect additional effective vaccines in near future along with advances in testing and therapeutics. "I called on Member States to reiterate their commitment to fair allocation of a #COVID19 vaccine. We mustn't leave any country behind in the response," Ghebreyesus said. Based on current projections, Pfizer and BioNTech expect to produce globally up to 50 million vaccine doses this year and up to 1.3 billion doses in 2021. The issue of challenges of distributing a potential vaccine such as the one being developed by Pfizer and BioNTech was also raised by Matshidiso Moeti, WHO's Regional Director for Africa. "The exciting news yesterday (Monday) of a possible effective vaccine becoming available presages significant cold chains challenges for African countries by the type of vaccine that that is. Which will need to be factored into the support to be provided," Moeti said. In his opening speech at the World Health Assembly on Monday, the WHO chief said that a vaccine is needed urgently to control the pandemic. "But as you know, it will not fix the vulnerabilities at its roots," he said. "A vaccine cannot address the global under-investment in essential public health functions and resilient health systems, nor the urgent need for a 'One Health' approach that encompasses the health of humans, animals and the planet we share. "There is no vaccine for poverty, hunger, climate change or inequality," the WHO chief said. /IANS