Caught between President Trump’s Election Day deadline and a skeptical American public, nine drug companies issued a joint pledge on Tuesday, promising that any Covid-19 vaccine they develop will be fully tested for safety before it’s released.

Chief executives of the pharmaceutical developers vowed to “always make the safety and well-being of vaccinated individuals our top priority.”

It’s an extraordinary pledge, coming “at a time when President Trump has repeatedly pushed for a quick vaccine timeline,” says CNN.

Nine biopharmaceutical companies sign a joint pledge to uphold "high ethical standards" around developing Covid-19 vaccines, suggesting they won't seek premature government approval https://t.co/UtxIPv9d1y

— CNN Breaking News (@cnnbrk) September 8, 2020

Trump wants a vaccine ready before Nov. 3, which he sees as vital to his re-election hopes.

The document is headlined “BIOPHARMA LEADERS UNITE TO STAND WITH SCIENCE.”

Those signing included top executives of AstraZeneca, Johnson & Johnson, Merck, Moderna, and Novavax, plus those leading two joint vaccine projects: Pfizer and BioNTech, and Sanofi and GlaxoSmithKline.

Drug makers are unaccustomed to having to reassure a skittish public about the safety of their medications.

But they are clearly feeling the pressure, not only from the White House but from the virus itself. As of Tuesday morning, there had been more than 6.3 million U.S. infections and nearly 190,000 deaths in the pandemic, according to the Johns Hopkins Covid-19 Dashboard.

This is what it’s come to: 9 drug cos send an unusual public letter, saying they agreed to submit the vaccines for clearance only when they’re shown to be safe and effective in large clinical studies to counter perception of political interference.https://t.co/Fov5ew5QAb

— Amy Siskind (@Amy_Siskind) September 8, 2020

The companies allowed themselves some wiggle room, reports the Washington Post:

“The statement left open the door for the use of partial data from the massive Phase 3 vaccine trials — which require the participation of at least 30,000 test subjects — to seek emergency-use authorization,” the Post says. “Such trials typically take years to complete and require lengthy follow-up to see how long protection from a vaccine may last.”

Three vaccine candidates, from AstraZeneca, Moderna and Pfizer/BioNTech, have already entered Phase III trials, with Johnson & Johnson expected to begin soon. All of the companies want to complete testing of their prospective vaccines for effectiveness and safety in record time.

“But public confidence in the shots has dropped as … Trump has repeatedly predicted that a vaccine could come before the Nov. 3 election,” says Politico.

The Post notes that the president’s own top vaccine adviser, Moncef Slaoui, told NPR last week that there’s “a very, very low chance that the trials that are running” could be completed “before the end of October.”

“More than 60 percent of voters think the U.S. should fully test any coronavirus vaccine — even if that delays rolling it out and allows the virus to keep spreading in the meantime,” according to a Politico/Morning Consult survey conducted in July.