In April, I signed up for the world’s first coronavirus vaccine trial. I was twice injected with the highest dose of mRNA-1273, an experimental vaccine made by the National Institutes of Health and the private biotechnology company Moderna. That vaccine candidate, along with a handful of others, has progressed to the final stage of clinical testing. If proved safe and effective, it may put a stop to the pandemic.

President Trump has promised a coronavirus vaccine will be approved next month and the public will have access to it “immediately.” Talk about an October surprise. At a White House news briefing on Sept. 18, he said “hundreds of millions of doses will be available every month, and we expect to have enough vaccines for every American by April.”

Overconfidence aside, a recent survey by the Pew Research Center found about half of Americans say they would not take such a vaccine. Across all age groups, ethnicities and education levels, confidence in future coronavirus vaccinations is plummeting. Concerns over side effects and effectiveness loom large. The White House launched Operation Warp Speed in the spring to accelerate a vaccine, but Pew finds nearly 9 in 10 Democrats are more worried that the process is moving too fast, not too slow. Nearly 7 in 10 Republicans agree.

To ward off this growing anxiety, the Food and Drug Administration may soon issue tougher standards for vaccine approval. But Trump has said he may reject such a plan, saying it “sounds like a political move.”

What’s the point of developing a vaccine at “warp speed” if most Americans refuse to take it? This crisis of confidence could undermine the entire vaccine development effort, at least in this country. It will get much worse if partisan actors — up to and including Trump — tie vaccine approval to a political deadline.

Science does not happen on a fixed schedule. It takes time to get things right. Interfering with that process for political purposes would not only be dangerous, but it would also be an insult to the tens of thousands of vaccine volunteers like me who have already taken on personal risk on behalf of others.

How should the vaccine timetable be set? By science, of course.

Phase 1 trials, like the one I am in, are designed to discover whether a vaccine is safe in a small number of healthy people. When I received the highest experimental dose of the Moderna vaccine, I suffered a fever of more than 103, nausea and other unpleasant side effects that lasted one day. But my reaction helped scientists discover the dose I had been given was probably too high. That high dose is no longer being tested.

Phase 3 trials, like the one my mother is enrolled in, establish whether a vaccine actually works in a much larger and more diverse population. At their core, such trials are surprisingly simple: Thousands of volunteers like my mom get injected with either a vaccine or a placebo, then they’re monitored to see whether they catch the virus as they go about their daily lives. If people who received the placebo get infections at a higher rate than those who got the real vaccine, we know the vaccine is protective. Phase 3 trials can also reveal whether a vaccine causes rare side effects that earlier trials didn’t turn up in smaller populations.

How do scientists decide when a Phase 3 trial is over? When a predetermined number of participants are infected. How many is agreed on ahead of time — the larger the number, the more confident we can all be in the protective power of the vaccine.

In a commendable act of transparency, the companies behind four of the leading vaccine candidates — Moderna, Astra-Zeneca, Pfizer and Johnson & Johnson — have publicly released their full Phase 3 trial plans, including the predetermined number of infections they are looking for. In clinical-trial speak, these infections are euphemistically called “events.” Each trial is recruiting tens of thousands of volunteers and is designed for between 150 and 170 events.

Few people know how many infections have occurred within these Phase 3 trials — that critical data is seen only by an independent monitoring board that is not beholden to the companies or the government.

But soon, regulators will receive updates about how the Phase 3 trials are going. It is at those crucial moments when partisan pressure could be applied.

There is a chance initial results will point unambiguously toward approval or rejection, but things could also be murky. The number of infections in the trials might not be high enough to know for certain whether the vaccine is working. But the president has already promised approval.

The FDA, led by Stephen Hahn, has the power to grant emergency approval based on incomplete clinical trial data. We must rely on the agency to do the right thing, even if it means missing Trump’s mid-October deadline. But if the FDA commissioner declines to approve a vaccine in October because of limited data, the secretary of health and human services, Alex Azar, may be able to override that decision. Such interference from the top down is what led to emergency use authorization for the unproven drug hydroxychloroquine earlier this year. Eventually, the FDA reversed that decision, explaining the malaria medication was “unlikely to be effective” against covid-19, the disease the novel coronavirus causes, and any potential benefit of taking it would not outweigh “known and potential risks.”

In a bid to boost public trust — and partly for fear politics might undermine it — nine leading companies in the vaccine race recently pledged not to seek approval or emergency use authorization for their vaccines until “demonstrating safety and efficacy through a Phase 3 clinical study that is designed and conducted to meet requirements of expert regulatory authorities such as F.D.A.” It’s a noble pledge, but only if they stick to it.

I hope we develop a safe and effective vaccine as soon as possible. I put my body on the line to help make that happen. But people will have confidence in a coronavirus vaccine only if science — not partisan politics — leads the way.