Ghana on Wednesday became the first country to receive vaccines from Covax, a global scheme to procure and distribute Covid inoculations for free to less developed or poorer countries.
Launched last April, Covax said it planned to ship two billion doses by year's end.
"The next phase in the fight against this disease can begin -– the ramping up of the largest immunisation campaign in history," UNICEF Executive Director Henrietta Fore declared in a statement.
"At last!" World Health Organization (WHO), Tedros Adhanom Ghebreyesus, whose organisation also backs the Covax initiative, said in a tweet.
"A day to celebrate, but it's just the first step."
The 600,000 doses delivered to Ghana are the Oxford/AstraZeneca formula, made under license by the world's largest vaccine manufacturer, the Serum Institute of India.
They are part of an initial tranche of deliveries headed to several low and middle-income countries.
An Emirates flight carrying the vaccines touched down at Accra's Kotoka International Airport shortly after 0740 GMT, where a government delegation led by the Minister for Health Designate Kwaku Agyeman Manu received them, in images broadcast on television.
Ghana's food and drug authority has already authorised the use of the Indian-made vaccines as well as Russia's Sputnik V, according to local media.
The West African nation has recorded 80,759 Covid-19 cases and 582 deaths since the start of the pandemic, although the true figure is believed to be higher because of lack of testing.
Vaccinations are scheduled to start on Tuesday in Accra, Kumasi and Obuasi.
They will begin with health workers and other frontline staff, adults over 60 and people with underlying health conditions, Information Minister Kojo Oppong Nkrumah said.
The first who will get the vaccines also include "frontline executive, legislature, judiciary and their related staff, frontline security personnel, some religious leaders, essential workers, teachers and other personalities," he said.
The government said it was making "frantic efforts" to acquire enough vaccines to inoculate all of Ghana's 30 million people and urged people to take part in the drive.
- New variants -
Covax, led by Gavi the Vaccine Alliance, the WHO and the Coalition for Epidemic Preparedness Innovations (CEPI), had expected a first round of deliveries in March with some early shipments occurring in late February.
For Ghana, it aims to deliver 2,412,000 doses.
Africa has been relatively spared by the pandemic.
It was the last continent except Oceania to reach the threshold of 100,000 deaths, which Europe crossed in April 2020.
To help speed immunisation of the continent's 1.3 billion people, the African Union said it had secured 270 million doses of anti-Covid vaccines for delivery this year.
The WHO on Monday accused wealthy countries of hogging Covid vaccines and hindering the pathway for poorer nations to get them too.
The health agency said some rich countries' direct deals with manufacturers had meant that previously-agreed vaccine allocations for poorer countries, via the Covax programme, were being reduced.
Some 145 participating economies are set to receive 337.2 million doses -- enough to vaccinate a little over three percent of their combined populations.
Covax has said it hopes to raise the figure to up to 27 percent in lower-income countries by the end of December.
New variants of the virus, including in neighbouring Nigeria, are spreading across the continent with the UK and South African variants recorded in cases in Ghana.
"It is strongly recommended for countries to use the AstraZeneca vaccine even if the... new variants are present," the WHO said in a statement last week.
In Ghana, schools reopened in January after a 10-month closure, but large social gatherings are banned and land and sea borders have remained closed since March 2020.
Economic growth is expected to have plummeted in 2020 to its lowest in three decades, to 0.9 percent according to the International Monetary Fund (IMF), from 6.5 percent in 2019.