CAMBRIDGE (CBS) — The CEOs of nine bio-pharma companies, including Moderna in Cambridge, have signed a pledge to maintain “high ethical standards and sound scientific principles” while developing a coronavirus vaccine.

The pledge said the F.D.A. has established clear guidance for vaccine development. Therefore, they will only submit a vaccine for approval or emergency use authorization after it has gone through phase three of a clinical study.

They also promised to create a sufficient supply and a range of options to make the vaccine accessible globally.

The other companies involved include Astra-Zeneca, Johnson & Johnson, BioNTech, GlaxoSmithKline, Merck, Novavax Inc., Pfizer Inc., and Sanofi.