A new survey is shedding light on the large number of employees who are reluctant to get vaccinated against COVID-19, reinforcing the challenge that company leaders face when it comes to promoting the vaccine to their workforce.

Nearly a quarter (24%) of employees say they will not get the vaccine, according to a new survey of more than 2,000 employees from the Employee Benefit Research Institute and independent research firm Greenwald Research. Nine percent say it depends, and 12% are still unsure about their vaccination decision. Overall, just over half (55%) say they are willing to receive a COVID-19 vaccine.

Related: HR’s next big job: Convincing employees to get COVID vaccines

When it comes to paying for the vaccine, 89% of survey respondents indicate they strongly or somewhat strongly feel that their insurance company should cover the vaccine’s full cost. Yet 50% strongly or somewhat feel they would be willing to pay $100 or less for the vaccine, and 28% are willing to pay more than $100.

“The American public is clearly conflicted about taking a COVID-19 vaccine, but not about who should pay for it,” Paul Fronstin, director of EBRI’s health research program and co-author of the report, said in a statement. “It does appear that those who are committed to taking the vaccine are willing to pay up to $100 for it, even if they feel the responsibility should lie elsewhere.”

The EBRI survey results—in line with other research that shows up to half of Americans are unsure about getting vaccinated against COVID-19—come as vaccines are getting closer to getting approved and rolled out in the United States.

Related: 7 questions HR is asking about COVID-19 vaccinations

Experts say that employers play a vital role in encouraging employees to get the vaccine, as well as distributing it. But employee hesitation and reluctance—as evidenced by the EBRI study—proves that might be a difficult challenge. “This is a complicated issue, with strong feelings for and against personally receiving the vaccine,” says Jaime Klein, founder and CEO of consulting firm Inspire Human Resources.

Still, employers would be wise to create a COVID vaccine plan and start encouraging employees to get vaccinated against the coronavirus.

“The distribution of COVID vaccines will be critical to getting back to business as usual,” says Michael Thompson, president and CEO of the National Alliance of Healthcare Purchaser Coalitions, a nonprofit, purchaser-led organization that represents some 12,000 employers. “Employers have a strong stake in ensuring the success of these public health efforts and can be a real ally in making it happen effectively.”

Other experts say communicating factual information about the vaccines to employees—including about safety and efficiency—and citing medical experts and organizations, like the CDC, can help. Tying the vaccine into wellness programs and offering employees incentives for taking it may also drive rates up.

Related: COVID-19 vaccine: What to know about communicating, legal compliance and more