A vaccine jointly developed by Pfizer and BioNTech has been 90 percent effective in preventing COVID-19 infections in ongoing Phase 3 trials, according to the companies in an announcement on Monday. Protection in patients was achieved seven days after the second of two doses, and 28 days after the first, according to preliminary findings.

"The first set of results from our Phase 3 COVID-19 vaccine trial provides the initial evidence of our vaccine's ability to prevent COVID-19," Pfizer chairman and CEO Albert Bourla said in a statement.

"We are reaching this critical milestone in our vaccine development program at a time when the world needs it most with infection rates setting new records, hospitals nearing over-capacity and economies struggling to reopen. With today's news, we are a significant step closer to providing people around the world with a much-needed breakthrough to help bring an end to this global health crisis. We look forward to sharing additional efficacy and safety data generated from thousands of participants in the coming weeks," Bourla said.

They're the first drugmakers to show successful data from a large-scale clinical trial of a coronavirus vaccine.