Sinovac says it will not take South Africa's shots.
Indonesia gives boosters to those vaccinated with Sinovac.
The Chinese shipments will help the sputtering global COVAX vaccine sharing programme which is far behind its pledge to deliver 2 billion doses this year following supply problems and export curbs imposed by major producer India.
It could also boost Beijing vaccine diplomacy efforts despite concerns over the efficacy of the Chinese shots, which have been turned down by some of the recipient countries or paired with boosters from Chinese manufacturers.
Of the 100 million Chinese vaccines, half will be provided by Sinopharm and half by Sinovac, with deliveries planned for July to September 2021, a WHO document says on July 29.
About 10 million Sinopharm shots had been sent by mid-August, a spokesperson for the Global Alliance for Vaccines and Immunization said Reuters. COVAX was co-lead by WHO throughout.
Sinopharm, Sinovac and China's trade minister did not answer to requests for comment about when Chinese vaccines would be delivered.
The Chinese vaccines have been allocated to 60 countries, mainly in Africa, which is expected to receive a third of the 100 million doses.
South Africa is listed by COVAX as one of the largest recipients of Chinese shots with an allocation of 2.5 million Sinovac doses, but a senior health official told Reuters the country was currently unable to accept the vaccines.
There is not enough information on effectiveness against the Delta variant and there is no data on Sinovac in people with HIV, said Nicholas Crisp, a deputy director-general in the health department who is overseeing the vaccine rollout.
We have not accepted COVAX Sinovac because it is premature in our evaluation and planning process, he told Reuters.
Sinovac did not immediately respond to a request for comment about South Africa's response.
A third recipient of Chinese vaccinations in Africa under COVAX with an allocation of nearly 8 million Sinopharm doses, has approved that vaccination, but has called it a possible option for the country's inoculation campaign.
A GAVI spokesperson declined to comment on South Africa and Nigeria and noted that other countries in the Round were not included, with one of the reasons being that some had decided not to receive the Sinopharm and Sinovac vaccines.
Officials from Kenya, Rwanda, Togo and Somalia, who are entitled to smaller COVAX shipments, said they had no concerns about the Chinese shots because they had been vetted by the WHO and more people need to be inoculated as soon as possible.
The decision by COVAX to give Chinese vaccines comes after the WHO gave emergency approval for the Sinopharm shot in May and Sinovac in June. GAVI has secured a combined supply of up to 550 million vaccines from the two companies until next year.
Including the Chinese vaccines, the facility expects to deliver about 500 million doses by the end of September, its latest forecast shows. It has so far shipped 215 million vaccines, mostly AstraZeneca's.
Ukraine is the only country in Europe on the ICOVAX list for China shots and is expected to receive about 160,000 Sinovac doses.
Some Chinese countries are expected to receive more than 25 million Sinovac vaccines, of which nearly 11 million Sinovac doses would go to Indonesia, making it the largest recipient of Chinese shots through COVAX. Other vaccines will go to countries in the Middle East and Latin America.
Indonesia will give vaccines, largely with the Sinovac vaccination, to health workers - who have been immunised with Moderna shots.
That mirrored similar moves in other countries that have deployed Sinovac shots, such as Brazil and Chile.
Healthcare workers are a small portion of those vaccinated in China but the booster policy has been interpreted by many as a sign of decreasing confidence in Indonesia.
Asked why Indonesia was buying the vaccine, of which Indonesia is a bilateral recipient also through major deals, an official at the Indonesian health ministry told Reuters: Sinovac could assure us of the amount they would deliver.