MANILA — A Russian official on Monday raised doubt on the safety of potential coronavirus vaccines developed by the US and the UK, as Manila and Moscow continued talks for a clinical trial.

The UK’s monkey adenovirus vaccine and the US messenger RNA “have never been studied longterm” and “have never received any approval before,” said Russian Direct Investment Fund (RDIF) CEO Kirill Dmitriev.

In contrast, the Russian coronavirus vaccine Sputnik V is a “modified” version of the human adenovirus vaccine against Ebola, he said.

“We based it on an already proven approach that has been tried on lots of people, including the US military,” said Dmitriev, whose organization funded the Russian vaccine development.

The UK and the US, he said, should publish studies showing that their vaccines “have no long term effects on increasing risk for cancer and infertility.”

“It’s just fair that we ask one question back because it’s about transparency , about honesty, and about people having information,” he said in an exclusive ANC interview.

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Last week, Britain's prestigious scientific journal Lancet published research that early tests of Sputnik V showed encouraging results.

Trial participants had “no significant side effects” and “on average developed 1.5 times the level of antibodies than a person who has been sick,” said Dmitriev.

Russia this week will apply for World Health Organization’s pre-qualification process for the vaccine, he said.

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Moscow and Manila are in talks for a clinical trial of Sputnik V. The Philippine health department last week stopped a planned trial in Cavite province for vaccines from the US and UK, pending approval from the local Food and Drug Administration.

“We are very eager to start our clinical trials in the Philippines,” said Dmitriev. “We believe it’s possible to start them this month.”

“We are in touch with your health ministry and once again, we agree that this issue should not be politicized. We should all be working together,” he added.

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The adenovirus vaccine enters people's cells and delivers the SARS-CoV-2 spike protein genetic code, helping the immune system "recognize and attack" the virus, said Denis Logunov of Gamaleya, the research institute that created Sputnik V.

The WHO insisted it would never endorse a vaccine that has not proven safe and effective and also said it did not expect widespread immunization against the novel coronavirus until mid-2021.

The organization said a total of 176 potential vaccines were being developed worldwide, including 34 being tested on people. Among those, 8 are at stage 3, the most advanced.

-- With reports from Agence France-Presse; Jamaine Punzalan, ABS-CBN News