Lower proportions of black and Asian staff at a hospital trust have come forward to have a Covid-19 vaccine, according to a study.
The analysis found 70.9% of white staff at the University Hospitals of Leicester NHS Trust had received the jab, compared with 58.5% of South Asian staff and 36.8% of black staff.
This could have "major implications" for vaccine roll-out, the report said.
A union said it was important to understand "any reasons for hesitancy".
The study, yet to be peer-reviewed, was co-authored by Prof Kamlesh Khunti, a diabetes expert from the University of Leicester who is also a member of the Scientific Advisory Group for Emergencies (Sage).
The trust, where 36% of staff are from minority ethnic backgrounds, has been running vaccination hubs for staff at each of its three hospital sites.
The report - which covers the period from 9 December to 3 February - found 12,278 staff from a total of 19,044 had come forward to have a jab since it was offered in mid-December.
Further analysis of the South Asian group found a much lower take-up among Pakistani and Bangladeshi healthcare staff (43.2%) than the Indian cohort (60.3%).
However the rate between Black Caribbean and Black African staff was quite similar.
The study also noted a lower take-up among staff under 30.
Staff in this age range made up 18.7% of the vaccinated group compared with 31.7% in the group who had not come forward for a jab.
The report said: "These findings give significant cause for concern, as ethnic minority groups (especially those working in healthcare) are at higher risk of infection with SARS-CoV-2 [coronavirus] and adverse outcome from COVID-19, yet are not taking up this critical preventative intervention.
"Furthermore, healthcare workers are an important source of health information for ethnic minority communities and so our findings may also have implications for vaccine uptake in the population at large."
The authors called for the findings to be "acted upon urgently to prevent the disparities caused by the COVID-19 pandemic from being allowed to widen further".
Professor Martin Marshall, chair of the Royal College of GPs, said: "We need to understand the reasons as to why there is hesitancy amongst people from BAME communities, so that it can be properly addressed.
"Some reasons we've been told include misinformation about the virus and vaccine, mistrust in health interventions more generally, and some people have said they want to wait until there is more certainty about the safety and efficacy of vaccines."
Sara Gorton, Unison's head of health, said: "Encouraging vaccination for all is the key to getting us out of this crisis. It's important to have as much understanding as possible about any reasons for hesitancy.
"Health workers gather information from many sources, so it's vital to ensure those they turn to are correct.
"NHS staff also need to be given time to ask vaccination teams about their concerns, talk to those who've had the jab and think things through. It can't just be a one-off opportunity."
Dr Habib Naqvi, director of the NHS Race and Health Observatory, said the organisation was "deeply concerned that vaccine uptake for Covid-19 is lower among black and minority ethnic hospital staff".
"Amongst those most at risk of dying from Covid-19 are also those that are most vaccine-hesitant," he said.
"More needs to be done to mediate and ensure accurate information, based upon facts, is targeted in culturally appropriate ways, to reach those who need the vaccination the most."
University of Leicester Hospitals NHS Trust said: "The data is two weeks old and three in four Leicester hospital staff have now been vaccinated, with uptake rising across all ethnic groups, and others taking up the offer of a jab in their local community.
"We want everyone to get the jab when they are called to do so."