I have never heard of this. The African National Congress (ANC), which fought against Apartheid for decades, had close ties with communist regimes in Angola and Mozambique. Those countries in turn had Cuban help in the fight against (South Africa-backed) right-wing rebels.

The South African government at the time was rabidly anti-communist -- think Eugene McCarthy and the red scare in the U.S. -- so I doubt they would have much to do with Cuba.

They also attacked French, and South Africans in Angola, btw, fyi

And then the apartheid croaked everywhere south of 17th parallel

That has no relation to vaccine production at all.

I'll add another trivia: they also throw you in jail if you speak badly of the current regime, which btw doesn't allow free elections.