Public confidence will be vital to a successful COVID-19 vaccine in the U.S., House Speaker Nancy Pelosi told a press briefing Friday.

Pelosi’s comments came amid the race for a COVID-19 vaccine, which gas been complicated by the upcoming Nov. 3 election. More than half of Americans indicated in a recent poll they would not get a vaccine before Election Day for fear politcs will result in the approval of an ineffective or unsafe treatment.

Top experts for the Centers for Disease Control and Prevention have placed the arrival of a broadly available vaccine in mid-2021, but President Donald Trump has insisted immunization will be available sooner. Democratic nominee Joe Biden said this week he trusts medical experts and vaccines, but not Trump.

"Unless there is confidence that the vaccine has gone through the clinical trials, and then is approved by the independent scientific advisory committee, as established to do just this, there will be doubts that people will have," Pelosi said.

A Pew Research Center study indicates Americans have doubts, with 51% saying they would definitely or probably get a COVID-19 vaccine if it were available today and 49% saying they would not get the vaccine today. Just four months earlier, 72% indicated their intention to get a COVID-19 vaccine.

Pelosi for the public to trust the vaccine, approval cannot be hurried.

"Those are the tests: safety and efficacy. And we want it to be available in a widespread, ethical way," she said. "And the best — it's not even an argument — but the best case for the vaccine is to have it as closely identified with the scientists who will be putting it forth."

Study results indicate Americans are concerned over the pace of vaccine production, with 78% saying their larger concern is that the process will move too fast without fully meeting scientific standards. Just 20% of people said they are worried the process will move too slowly.

Moderna and Pfizer released their clinical trial protocols this week to boost public confidence in their vaccine candidates. It normally takes years to develop a vaccine. Work on a coronavirus vaccine began earlier this year although some of the candidates are based on research that began with the 2002 SARS epidemic.