The Philippines will be the first country in the world to begin large-scale human testing of Russia's coronavirus vaccine in October. President Rodrigo Duterte is expected to be inoculated as early as May next year.
Duterte had offered himself as a guinea pig for the first jab, saying he had "huge trust" in the vaccine. But his spokesman Harry Roque confirmed he will not receive the inoculation until regulators guarantee its safety.
There is growing scepticism about the effectiveness of the fast-tracked vaccine.
Phase 3 clinical trials in the Philippines are due to run from October to March 2021.
Roque said the president was scheduled to receive the vaccine no earlier than May 1.
Roque said Philippine experts will review next month the results of Russia's Phase 1 and 2 clinical trials before the Southeast Asia country starts its Phase 3 testing.
"We will do it simultaneously with Russia," Roque said.
On Tuesday Russia became the first country to grant regulatory approval for a Covid-19 vaccine, to be named "Sputnik V" in homage to the Soviet Union's launch of the world's first satellite.
Philippines' Food and Drug Administration is expected to approve the coronavirus vaccine - developed by the Gamaleya research institute and the Russian defence ministry - in April.
"May 1 is when the PSG (presidential security group) may allow him, once all requisite tests have been finished," Roque said.
Moscow said it has developed the world's first vaccine offering "sustainable immunity" against the coronavirus and is in the final stage of tests involving 2000 people.
The Philippines has logged the highest number of confirmed infections in Southeast Asia with more than 147,500 cases and at least 2400 deaths.
Anna Lisa Ong-Lim, an infectious disease professor at the University of the Philippines College of Medicine, said the Government's timeline to have a vaccine available by May was "very optimistic".
Despite scepticism surrounding Russia's vaccine development, the World Health Organisation (WHO) said it was looking forward to reviewing clinical trials.
The WHO said 28 of more than 150 potential vaccines are being actively tested on humans, of which six have reached the final Phase 3, when candidate drugs are tested on large groups of people.
"WHO is in touch with Russian scientists and authorities, and looks forward to reviewing details of the trials," the United Nations health agency said.
"WHO welcomes all advances in Covid-19 vaccine research and development."