One in 10 Irish people say they would not take any new vaccine that could prevent Covid-19.
A study by psychologists at Maynooth University and Trinity College found just 65% would definitely use it.
The researchers say it is a "worryingly low" level.
Dr Fréderíque Vallières, director of the Trinity Centre for Global Health, says they are going to investigate further.
"There were a healthy number of individuals - over 60% - who said that they would accept a vaccine for themselves or for their children should it become available.
"We did find about one in four who said that they would maybe consider it and then about 10% who said that they wouldn't consider it.
"In this next wave of surveys that we are hoping to conduct in the next couple of weeks, we hope to explore that further."
Dr Vallières said that vaccines and immunisations are important to reach herd immunity.
"So to make sure there is a sufficient number of the population that is protected by the vaccine so that we can actually protect those who cannot access them or are too vulnerable to access them."