“Four vaccines have been approved for moving into clinical trials... and another six are in the pipeline for us to review,” Hahn said during a press briefing on Tuesday.

The US Administration launched in May Operation Warp Speed, a joint project of Health and Defense Departments, which aims to deliver 300 million doses of a vaccine for COVID-19 by January 2021.

The country’s top pandemics expert Anthony Fauci warned on Tuesday, however, that there is no certainty the United States will be able to develop a vaccine against COVID-19 that works and will be safe.

Data on vaccine effectiveness, he added, may be available in the winter or early next year.