Russia’s coronavirus vaccine will be gradually rolled out to high-risk people before a mass vaccination of Russians begins in October, the head of the group funding the research said on Wednesday.

Russian President Vladimir Putin announced the approval of a coronavirus vaccine for use on Tuesday, claiming it as a “world first,” amid continued concern and unanswered questions over its safety and effectiveness.

Speaking to CNN’s Anderson Cooper and Dr. Sanjay Gupta on Tuesday, Russian Direct Investment Fund (RDIF) head Kirill Dmietriev said “safety is at the core of the vaccine.”

“We know the technology works and we will publish the data in August and September to demonstrate that,” Dmietriev said.

Developed by the Moscow-based Gamaleya Institute, the vaccine has yet to go through crucial Phase 3 trials in which it would be administered to thousands of people.

Russia hasn’t released any scientific data on its testing and CNN is unable to verify the vaccine’s claimed safety or effectiveness.

“The rollout in Russia will be very gradual. We are not going to give it to 10 million people tomorrow,” Dmietriev said, adding that frontline medical workers and people who are at high risk of contracting the coronavirus will be first in line to voluntarily receive the vaccine.

Following a planned mass rollout among Russians in October, Dmietriev said the vaccine will be made available to other countries around November. He claimed they have already received pre-orders for a billion doses of the vaccine.

Brazil’s Parana state is set to sign a cooperation agreement for testing the vaccine, according to a statement from the Russian Embassy.

“Brazil is aware of all the vaccine studies under development and guarantees that, as soon as it has access to a vaccine that is proven to be effective against Covid-19, Brazilians will have access to it,” the Brazil Health Ministry told CNN on Wednesday.

Philippine President Rodrigo Duterte has also backed Russia’s Covid-19 studies, saying in a Monday news briefing that he would volunteer to take the first dose of the vaccine in public, according to CNN affiliate, CNN Philippines.

His comments came after Moscow offered to supply the vaccine to the Philippines. The Philippine Department of Health reportedly said its officials were in talks with the RDIF over doses and setting up manufacturing laboratories in the Philippines. But any vaccine would need to go through local processes and Philippine Food and Drug Administrationapproval, the President said, according to CNN Philippines.

Russia insists vaccine is safe but questions abound

Putin’s claim of victory in the global race to create an effective Covid-19 vaccine comes amid suggestions that Russia cut essential corners in its development.

Russia enacted a law in April which eliminated the requirement for Phase 3 trials to be conducted before approval. This has allowed researchers to fast-track the vaccine development process.

Dmietriev said that during a pandemic, the law allowed them to run phase 3 trials concurrently “with launching the vaccine to high-risk groups, which we are doing,” adding “we believe it is exactly the right approach.”

Phase 3 trials are set to start on Wednesday in Russia with 2,000 participants. The United Arab Emirates, Saudi Arabia, Brazil and Mexico will begin the trials on August 12, according to the new Sputnik V website.

Experts have voiced unease over releasing a vaccine before it was fully tested.

“The bar is necessarily set very high for criteria that must be satisfied for approval after Phase 3 clinical trials,” Danny Altmann, Professor of Immunology at Imperial College London, told the Science Media Centre. “The collateral damage from release of any vaccine that was less than safe and effective would exacerbate our current problems insurmountably. I hope these criteria have been followed. We are all in this together.”

On Tuesday, Dr. Anthony Fauci, director of the US National Institute of Allergy and Infectious Diseases, said he had serious doubts the Russian vaccine is ready for widespread use.

“I hope that the Russians have actually, definitively proven that the vaccine is safe and effective. I seriously doubt that they’ve done that,” Fauci told Deborah Roberts of ABC News for a National Geographic event to broadcast Thursday. A portion of the interview was posted by National Geographic on Tuesday.

Fauci said that having a vaccine and proving it is safe and effective are two different things.

“We have half a dozen or more vaccines,” he said. “So if we wanted to take the chance of hurting a lot of people or giving them something that doesn’t work, we could start doing this, you know, next week if we wanted to. But that’s not the way it works.”

Six pharmaceutical companies, including Moderna and Pfizer, have reached deals with the US government to develop a Covid-19 vaccine as part of a federal push to curb the pandemic. The US Food and Drug Administration (FDA) has previously said it would only approve a vaccine if it meets a 50% efficacy requirement.

US Health and Human Services Secretary Alex Azar said on Tuesday that the United States has strict safety standards and “this is not a race to be first.”

“We will require any vaccine in the United States be safe and effective and meet the FDA’s gold standard,” Azar said during a news conference from Taipei, where he was meeting with Taiwanese leaders to discuss Covid-19.

Azar said that two of the six vaccines the US government invested in entered Phase 3 clinical trials weeks ago, and he noted that data from the initial Russian trials has not been disclosed.

In a statement emailed Tuesday, the World Health Organization said it is in contact with Russian scientists and authorities and looks forward to reviewing details of the trials. According to WHO, there are 28 vaccines in human trials around the world.