Key workers in 145 countries must get Covid-19 shots by June-end: WHO nch health workers carry a patient on a stretcher from Mulhouse hospital before a helicopter transport on March 23, 2020. Reuters file photo UNB, Dhaka UNB, Dhaka With the rollout of the Covid-19 vaccination programme, the United Nations has urged key workers and other vulnerable people in 145 countries to get immunised by the first half of this year. The aim of yesterday's announcement by the World Health Organization (WHO) is to help governments chalk out their vaccine distribution programmes, by providing details about which vaccine they can expect to receive between now and June-end.