eSwatini will no longer use AstraZeneca's Covid-19 vaccine, its health minister said on Tuesday, after a trial showed it gave minimal protection against mild-to-moderate Covid-19 caused by the dominant variant in South Africa.

eSwatini, a tiny kingdom formerly known as Swaziland that borders South Africa, was due to receive AstraZeneca doses from the COVAX Facility, the global vaccine distribution scheme co-led by the World Health Organization (WHO).

South Africa on Sunday put on hold the rollout of AstraZeneca's shots, after researchers published preliminary data showing the vaccine had significantly reduced efficacy against the more contagious 501Y.V2 variant first identified late last year.

The researchers did not assess whether the AstraZeneca vaccine protects against severe Covid-19, and the South African government is consulting experts on how to proceed with the 1-million doses it already has received.

"The country has considered its close proximity with South Africa. We felt that the variant could be in the country already. We will no longer be using the AstraZeneca-Oxford vaccine," Minister Lizzie Nkosi said in an interview on local television.

"The change will mean that the government will be in talks with other suppliers," she added, saying eSwatini would consider doses from Pfizer or any other shot endorsed by the WHO.

AstraZeneca's chief executive said on Tuesday that his company believed its vaccine should still protect against severe Covid-19. The British-Swedish firm said earlier that it was adapting its vaccine to the 501Y.V2 variant.

eSwatini had hoped to receive enough vaccines for 20% of its 1.3 million population via the COVAX facility free of charge and wanted to buy additional doses for the rest of its people either via COVAX or other sources.

It has recorded more than 16 000 Covid-19 cases during the pandemic and 610 deaths.

Its Prime Minister Ambrose Dlamini died in a South African hospital in December after testing positive for Covid-19.