WENDELL ROELF and ALEXANDER WINNING SOUTH Africa agreed to onerous conditions like non-refundable down payments to secure COVID-19 vaccines from Johnson & Johnson (J&J) and Pfizer, its health minister said on Wednesday, describing terms vaccine manufacturers had demanded as "difficult and sometimes unreasonable". The country worst-hit by the pandemic on the African continent in terms of coronavirus infections and deaths is counting on the single-dose J&J and double-shot Pfizer vaccines to ramp up immunisations after a slow start. It has signed deals with the two firms for a combined 61 million doses, enough to vaccinate 46 million people out of…