The statement is meant to reassure the public that the companies will not seek a premature approval of vaccines under pressure from the Trump administration.
A group of drug companies competing with one another to be among the first to develop coronavirus vaccines are planning to pledge early next week that they will not release any vaccines that do not follow rigorous efficacy and safety standards, according to representatives of three of the companies.
The statement, which has not yet been finalized, is meant to reassure the public that the companies will not seek a premature approval of vaccines under political pressure from the Trump administration. President Trump has pushed for a vaccine to be available by October — just before the presidential election — and a growing number of scientists, regulators and public health experts have expressed concern over what they see as a pattern of political arm-twisting by the Trump administration in its efforts to combat the virus.
The companies’ joint statement was planned for early next week, but it may be released before then after its existence was made public on Friday by The Wall Street Journal. The manufacturers that are said to have signed the letter include Pfizer, Moderna, Johnson & Johnson, GlaxoSmithKline and Sanofi.
The pharmaceutical companies are not the only ones pushing back. Senior regulators at the Food and Drug Administration have been discussing making their own joint public statement about the need to rely on proven science, according to two senior administration officials, a move that would breach their usual reticence as civil servants.
Scientists have been rushing at record speed to develop a vaccine that could end the pandemic, which has taken nearly 190,000 lives and infected more than six million people in the United States. Three companies — Moderna, Pfizer and AstraZeneca — are testing their candidates in late-stage clinical trials.
Pfizer’s chief executive said this week that the company could see results as early as October, but the others have said only that they plan to release a vaccine by the end of the year.
Public health experts have applauded the companies’ rapid development of a vaccine, and early results have been promising. But in recent weeks, they have grown worried as Mr. Trump and his allies have begun talking about a vaccine that could be ready before the election on Nov. 3.
Even as companies are competing to be the first to bring a coronavirus vaccine to market, they must navigate perilous political terrain. If they are among the first to bring a successful vaccine to market, they could earn major profits and help rehabilitate the image of an industry battered by rising drug prices.
But if a vaccine turns out to have dangerous side effects for some people, the fallout could be catastrophic, damaging their corporate reputations, putting their broader portfolio of products at risk and broadly undermining trust in vaccines, one of the great public health advances in human history.
In tweets and public comments, Mr. Trump has explicitly tied his re-election fortunes to a vaccine, an idea detailed last week at the Republican National Convention, where promotional videos featured the administration’s efforts to fund and develop one in its crash program called Operation Warp Speed.
Trump campaign advisers have privately called a pre-election vaccine “the holy grail.”
Also last week, the Centers for Disease Control and Prevention sent letters to public health agencies around the country asking them to prepare for the possibility that a vaccine could be ready by late October or early November.
And on Friday, even as federal health officials had been tempering expectations about when a vaccine would be ready, Mr. Trump said one would “probably” be ready in October. Even the companies can’t see the results while the trials are underway, but he promised, “You are going to see results that are shockingly good.”
Just the day before, Dr. Moncef Slaoui, the top scientist on Operation Warp Speed, warned in an interview with National Public Radio that the chance of successful vaccine results by October was “very, very low.”
Scientists within the federal government and outside of it say they are dismayed by what they see as meddling by the Trump administration in the federal pandemic response, from the president’s misguided promotion of hydroxychloroquine as a treatment and his exaggeration of the benefits of convalescent plasma to the C.D.C.’s changing guidance on who should be tested.
Several top health officials have made it explicit in recent weeks that they would rather quit than be co-opted by the White House in approving a vaccine.
Dr. Slaoui told Science magazine on Thursday that he would “immediately resign if there is undue interference in this process,” though he said there had been none so far.
In a conference call last month, Dr. Peter Marks, who heads the F.D.A. division that approves new vaccines and treatments, made the same pledge to members of a vaccine working group at the National Institutes of Health.
“If something is not safe enough and effective enough for my family, there’s no way I’m going to stand by and see it given to the rest of the country,” Dr. Marks said in an interview on Thursday. “It’s not going to happen under my watch.”
Dr. Stephen M. Hahn, the F.D.A. commissioner, has repeatedly said his decisions are based on scientific data alone. He has publicly committed to vet any vaccine approval through an advisory committee of outside experts, who typically review clinical trial data before a new vaccine is approved.
Senior F.D.A. officials, including political appointees, have been frustrated by comments Mr. Trump has made in recent weeks about his efforts to speed along approvals, giving the impression the White House is playing a regulatory role.
At his news conference Friday, Mr. Trump said he had just spoken to the head of Pfizer, describing him as a “great guy” whose company is a leader in the race to develop a vaccine.
In a separate appearance on Friday, the president said pharmaceutical companies had told him that “if this was a more typical kind of president, getting these approvals would take two or three years.”
With vaccines, Mr. Trump’s ability to influence the approval process has its limits. While a government agency, such as the C.D.C., can request vaccine approval, requests typically come from the drug makers.
Companies have separately sought to underscore their commitment to rigorous scientific review.
On Monday, AstraZeneca’s chief executive, Pascal Soriot, released a statement acknowledging recent questions about the speed of vaccine development. “I want to reiterate my commitment that we are putting science and the interest of society at the heart of our work,” he said. “We are moving quickly but without cutting corners.”
And on Friday, Moderna’s chief executive, Stéphane Bancel, told CNBC that the company was slowing enrollment in its trials to include more people from groups at high risk for Covid-19. “I would rather we have higher diverse participants and take one extra week,” Mr. Bancel said in the interview.