The global organisations that buy Covid vaccines for poorer countries "need to step up" and order doses from Africa's only Covid vaccine maker in order to save the production line, the company's senior executive told the BBC.
This follows warnings from Aspen Pharmacare that it may have to stop production at its South African plant.
It has been hit by low demand.
Fewer than one in six Africans have had two doses of a coronavirus vaccine, with many reluctant to get jabbed.
The continent's top health body has also urged those buying the jabs for Africa to place orders with Aspen.
Last November, Aspen negotiated a licensing deal to package and sell Johnson & Johnson's vaccine for distribution across Africa.
At the time, the deal was seen as a major boost for African countries which received far fewer doses than richer parts of the world.
South African President Cyril Ramaphosa said on Wednesday that he was working with his counterparts in Kenya, Rwanda, Egypt and Ghana in order "to make sure that vaccines that will be used on our own continent are actually bought from companies that make vaccines here".
But Aspen's group senior executive Stavros Nicolau told the BBC that purchases from African governments alone would not be enough to save the Covid vaccine production line in South Africa.
He said that Covax - the UN-backed body set up to get more jabs to less well-off countries - should have done more to buy doses from the African producer.
Mr Nicolau said that none of the two billion doses purchased by Covax came from the continent.
Global procurers "need to step up" and change where they are buying from, he added.
Africa's fully vaccinated stands at 16%
But the global vaccine alliance, Gavi, which is responsible for procurement on behalf of Covax, said the issue is currently one of demand.
Initially, in 2020 and 2021, as Aspen was "part of the broader manufacturing network for the Johnson & Johnson vaccine", Gavi had no say over how much each company would supply to Covax, a Gavi spokesperson said.
Now, however, Aspen has a licence to produce and sell Johnson & Johnson's Covid vaccine under the brand name Aspenovax.
But Gavi has said that while it welcomes this development, a lack of demand means that it is "not in a position to order large quantities of vaccines".
A number of countries around the world have seen falling vaccination rates, and figures from the Africa Centres for Disease Control and Prevention (Africa CDC) showed that just 16% of people on the continent are fully vaccinated.
Some experts blame concerns over the safety and efficacy of Covid vaccines for the slow uptake in many African countries.
However others argue that after struggling to get vaccines, Africa experienced a glut of supply which was difficult to use in the required time, and some have had to be destroyed.
The production of vaccines in Africa was seen as key to vaccine equity and making the continent less dependent on the global North to fight this and future pandemics.
When Aspen Pharmacare completed the deal with Johnson & Johnson allowing it to make Aspenovax, the World Health Organization hailed it as a "huge leap forward''.
And yet today, Aspen still finds itself in a position where it needs buyers from outside the continent in order for its Covid vaccine production to survive.
"The irony is not lost," Mr Nicolau said, adding that "there is still a dependence" on countries and agencies outside Africa.
Buying from African producers "is a political decision", argues Dr John Nkengasong, the head of Africa CDC, which oversees the continent's Covid response.
He told the BBC's Newsday programme that rather than being viewed as charity, it should be "part of global strategies to get rid of this and subsequent pandemics".