JOHANNESBURG, Aug 20 (Reuters) - South Africans formed queues hundreds of metres long to get their COVID-19 shots on Friday, after the government made vaccinations available to all adults in order to hasten a rollout beset by challenges and delays. South Africa has been battered by three coronavirus waves, infecting at least 2.65 million people, killing 78,000 - by far the continent"s worst toll - and pummelling an already struggling economy with lockdowns and travel restrictions. On Friday, authorities opened up vaccinations to 18 to 35 year-olds. About 8% of South Africa"s population of 60 million is fully vaccinated, and 14% have received one shot. "I just wanted to get it out the way. I"ve been waiting so long for it," 23-year-old medical student Lisa Heyneke said, shortly after receiving her shot in Johannesburg. South Africa"s campaign got off to a slow start, owing to bureaucratic hiccups, a failure to start early talks with pharmaceutical companies, and bad luck - it ditched a million AstraZeneca shots on evidence they may not work against its dominant variant, only for that evidence to be later overturned. Like other African countries, it also been at the back of a queue favouring rich Western nations. read more At Cape Town"s convention centre, the line of people was a mile long, while dozens of cars queued at a drive vaccination venue at converted car racing track in north Johannesburg. Challenges remain such as vaccine hesitancy and the difficulty of getting vaccines out to remote areas, Mary Kawonga, chair of the COVID-19 Advisory committee for Gauteng, the province around Johannesburg, told Reuters at the venue. On Thursday, a Johannesburg University survey showed vaccine acceptance improving to nearly three quarters of the population last month, compared with two thirds at the start of the year. Donald Mgimeti, 45, was initially unsure. Then, in May, he was shocked by the death of a friend from COVID-19. "It made me realise how serious this is," he said, rolling down his sleeves after his jab. Additional reporting by Mike Hutchings in Cape Town Editing by Raisa Kasolowsky Our Standards: The Thomson Reuters Trust Principles.