The pledge was made following growing concerns about a rushed approval of a coronavirus vaccine after US President Donald Trump predicted a vaccine could be available by the end of the year.
The chief executives of nine companies developing vaccines against COVID-19 have pledged to "uphold the integrity of the scientific process", amid concerns US President Donald Trump will pressure regulators to approve a vaccine ahead of the presidential election in November.
"We, the undersigned biopharmaceutical companies, want to make clear our ongoing commitment to developing and testing potential vaccines for COVID-19 in accordance with high ethical standards and sound scientific principles," said the CEOs.
The statement was signed by AstraZeneca, BioNTech, GlaxoSmithKline, Johnson & Johnson, Merck, Moderna, Novavax, Pfizer and Sanofi.
Specifically, the companies said they would only seek emergency authorisations for vaccines "after demonstrating safety and efficacy through a Phase 3 clinical study that is designed and conducted to meet requirements of expert regulatory authorities such as FDA," the Food and Drug Administration.
Some experts and former officials of this agency worry it has become politicised after it issued emergency use authorisations for two COVID-19 treatments without sufficient proof.
Both hydroxychloroquine, whose authorisation was later revoked over safety fears, and blood plasma from recovered COVID-19 patients, were touted by Mr Trump.
Joe Biden, the Democratic candidate for president, has accused Mr Trump of "undermining public confidence" by regularly raising the possibility a vaccine will be ready ahead of the election on 3 November.
Stephen Hahn, the head of the FDA, has also guaranteed that only science will decide when a vaccine is ready.
In theory, the FDA has to rely on independent expert committees that oversee clinical trials before they give their green light. The makers themselves must also apply for authorization.
Among the companies, Moderna and Pfizer are in the most advanced stages of their trials, and the US Centers for Disease Control and Prevention (CDC) has asked states to have distribution networks ready by 1 November.
The widely-respected Anthony Fauci, director of the National Institute of Allergies and Infectious Diseases, has said the results of clinical trials aren't expected to be known until the final two months of the year.
"I think it's extremely unlikely but not impossible," that the trials will have results to show before the election, Moncef Slaoui, the scientific head of the White House program tasked with producing and delivering vaccine doses, told NPR.