If offered a coronavirus vaccine free of charge, fewer than half of Black people and 66% of Latino people say they would agree to take it, according to a survey-based study that underscores the challenge of getting vaccines to communities hit hard by the pandemic.

The survey released Monday is one of the largest and most rigorous to date. Other recent studies have also pointed to vaccine hesitancy in communities of color, but Monday's survey delved deeper into the reasons, polling respondents on a spectrum of questions to get at the roots of their distrust.

Perhaps its most sobering findings: Only 14% of Black people trust that a vaccine will be safe, and 18% trust that it will be effective in shielding them from the coronavirus. Among Latinos, 34% trust its safety, and 40% trust its effectiveness.

The survey was conducted Sept. 1 through 15, before interim analyses were released showing that three experimental vaccines had achieved high levels of protection against the coronavirus and appeared largely safe.

The study's authors said trust in vaccine safety is especially critical and was found in subsequent questions to be by far the strongest predictor of whether people are willing to take the vaccine.

Vaccinating a large share of the U.S. population will prove pivotal to establishing national immunity to the novel coronavirus and slowing the spread of the pathogen, infectious-disease specialists say. To reach the threshold necessary to establish herd immunity, a majority of Americans will likely need to be vaccinated in coming years.

» READ MORE: COVID-19 pandemic is not halting everyone’s Thanksgiving travel plans

But even as pharmaceutical companies release encouraging data on three experimental vaccines and officials throughout the country build a complex infrastructure of distribution chains and ultracold freezers, it is becoming increasingly clear the country will face profound challenges in trust and uptake of the vaccine.

“It’s not having a vaccine that saves lives, it’s people actually getting vaccinated,” said Michelle Williams, dean of the Harvard T.H. Chan School of Public Health, who cofounded the COVID Collaborative, the nonprofit that commissioned the study. “For that to happen, we need to understand why so many are hesitant and help overcome that.”

Getting coronavirus vaccines to communities of color is especially important because those communities have disproportionately borne the burden of the pandemic.

Nearly nine months after the virus exploded in the United States, Black, Asian, Native American and Hispanic patients still die far more frequently than White patients, even as death rates have plummeted for all races and age groups, The Washington Post found, after analyzing the records of 5.8 million people who tested positive for the virus from early March through mid-October.

Officials are wrestling with how to ensure that vulnerable populations receive the vaccine. Almost certainly at the top of the list: about 21 million front-line health-care workers. But after them will probably be other essential workers, many of whom come from Black, Latino and Asian communities. Many can't work from home, don't have transportation and live in crowded housing.

For many Black people, the lack of trust in the coronavirus vaccine is rooted in history, some experts said.

"On one hand in this country, you have the anti-vaxxers and the unfounded disinformation they push," said Alexandre White, an expert at Johns Hopkins University who studies the sociology and history of epidemic response. "But what you see from minorities is a hesitancy that is quite rooted in historical reality."

The bodies of Black people who were enslaved were used by medical schools for anatomy dissections. Black women were used for gynecologic research, experimentation and sterilization, White noted.

At a meeting last month of Food and Drug Administration officials and vaccine experts, the worries of several people of color were read aloud from a recent focus group on vaccines:

"I firmly believe that this is another Tuskegee experiment."

"I would not be first in line and I would want to see some data."

"We are not going to be guinea pigs again."

For many in the Black community, the Tuskegee syphilis study — a secret experiment conducted by the U.S. government to study the deadly venereal disease without treatment — looms especially large in the collective memory, experts said.

Monday's survey — which found 48% of African Americans willing to get the vaccine — found that knowledge of the Tuskegee study was among the predictors for whether a Black respondent would be willing to take the vaccine. Other factors included strength of their racial identity, previous flu vaccine experience, partisanship, sex, age and education.

For Latino people, similar factors were the main predictors in vaccine acceptance. But also included was their level of trust in the government to look out for the best interests of Latino people and whether the individual lived in the suburbs.

The survey was conducted by Langer Research, a New York-based survey research firm that collaborates with The Washington Post on its joint ABC-Post polls.

The study collected questionnaire responses from 1,050 Black and 258 Latino adults. The respondents consisted of a nationally representative random sample administered online.

The same group that sponsored the study also announced a partnership Monday with the Ad Council to combat vaccine hesitancy in communities of color.

"America needs to do more to tap ingenuity and expertise, particularly at this time of national crisis and presidential transition," said John Bridgeland, cofounder of the COVID Collaborative.

While the survey studied only the Black and Latino communities in depth, the nonprofit that commissioned the report and other experts have expressed similar concerns about vaccine hesitancy among Native Americans, Asians and other minority groups.

Other efforts in recent weeks have shown the hurdles and resistance such efforts may encounter.

When the presidents of two historically Black colleges announced they were volunteering as test subjects for an experimental vaccine for the coronavirus, they were met with backlash from Black parents and accusations that they were condoning experimentation on the Black community.

The men's decision to share their participation in the trials is part of an effort among African American leaders to address the mistrust they worry puts communities of color in greater danger.

» Here are Philly’s current COVID-19 guidelines: inquirer.com/phillyguidelines

Others Black leaders have tried to address the mistrust.

Michigan's lieutenant governor, Democrat Garlin Gilchrist II, tweeted about his recent flu shot. And the Rev. Jesse Jackson said at his 79th birthday celebration last month in Chicago that his wish was that people of color protect themselves from the virus by following public health protocols.

A similar survey by the Kaiser Family Foundation and the Undefeated last month similarly found that 49% of African Americans said they would not take a vaccine even if scientists deemed it safe and made it free to anyone who wants it.

That hesitancy comes despite people in communities of color being much more likely to know someone who has suffered from COVID-19, the illness caused by the coronavirus.

In Monday’s survey, 55% of Black people said they knew someone diagnosed with COVID-19, and 48% knew someone who had been hospitalized with or died of COVID-19. The numbers were even higher among Latinos, with 73% knowing someone diagnosed and 52% knowing someone who had been hospitalized or died from COVID-19.

Howard University President Wayne A.I. Frederick, a physician, said Black health-care providers need to stress the importance of vaccinations in their communities so they feel confident about receiving them.

"The average African American cannot give you details of Tuskegee. Their mistrust is of institutions, of government institutions, of law enforcement, and that mistrust spreads across our community," Frederick said. He was one of several leading Black medical experts who have united to form the Black Coalition Against COVID-19 and held a news conference last week.

The study found that African Americans were twice as likely to trust a messenger from their own racial group compared with a White counterpart.

"The best messengers are going to be influencers from within their own communities," said Williams, from Harvard. "And very clearly, personal physicians from minority communities are going to be very important in this effort."

The Washington Post’s Ariana Eunjung Cha and Lena H. Sun contributed to this report.