The World Health Organization (WHO) has urged African countries not to destroy Covid-19 vaccines that may have passed their expiry date.
Countries have been told to keep hold of them and wait for further guidance.
The appeal comes after Malawi and South Sudan said they would destroy more than 70,000 doses of the Oxford-AstraZeneca jab because they expired in mid-April.
But the Africa Centres for Disease Control (Africa CDC) said it had been assured the doses were safe to use.
Many vaccines can be used up to 36 months after manufacture, but because Covid-19 jabs are so new there is not enough data to prove their effectiveness over longer periods.
The final decision on whether to use expired jabs rests with national drug regulators, the BBC's health reporter in Nairobi, Rhoda Odhiambo, notes.
The rollout of coronavirus vaccines across Africa has been slow, partly because of supply issues and wider scepticism about the jab.
"My appeal to member states is: if we are doing our part to mobilise these vaccines, you do your part and use the vaccines," John Nkengasong, director of the Africa CDC, told a news conference on Thursday.
Malawi said it planned to destroy more than 16,000 doses of the AstraZeneca vaccine, which were manufactured by the Serum Institute of India (SII), because their expiry date was 13 April.
South Sudan, meanwhile, planned to discard some 59,000 doses for the same reason.
The vaccine doses were donated to 13 African countries through a partnership between the African Union (AU) and the telecommunication company MTN Group, the BBC's Peter Mwai from Reality Check reports.
The AU bought one million doses of the AstraZeneca vaccine from South Africa, which had stopped using the jab amid doubts over its effectiveness against a new variant that had become dominant in the country.
The Africa CDC sent the doses to countries in late March, a few weeks before they expired.
Mr Nkengasong, who called the vaccine landscape "extremely challenging", said the SII had advised Africa CDC that the "vaccines can still be used even after nine months".
The WHO's Africa regional director Matshidiso Moeti urged countries to "store the vaccines safely as we continue to study and try to get definitive advice on whether the vaccines can be used for longer".
Other than Malawi and South Sudan, the WHO said Ghana and Sierra Leone had also not used all of their vaccines due to their expiry dates.
Sierra Leone's health minister said the country had been left with about a third of the doses they received. "We had to scramble to make sure that we prioritise the use of these vaccines," Austin Demby told the BBC.
Out of 55 African countries, 41 have benefitted from the delivery of vaccines via the global-sharing scheme Covax. Seven are yet to receive their first batch.
The Covax scheme aims to ensure vaccines are shared fairly among all nations, rich and poor. So far, more than 38 million doses of vaccine have been delivered to 98 countries.
Health experts say equitable global access to vaccines is crucial to ending the pandemic.