Patients of a Tasmanian medical clinic may have been given less effective vaccines across two decades, with a probe revealing there was no documented evidence the facility followed national storage guidelines.

The state's Department of Health is working with Dodges Ferry Medical to provide advice to people who were vaccinated at the clinic between July 2003 and March 22, 2023.

An investigation by the state director of public health found there was no documented evidence of vaccines being stored per national guidelines during that period.

The department says it is possible vaccines may have been exposed to temperatures in storage that were too hot or too cold, which can reduce their effectiveness in preventing disease.

"There is no risk of harm to people who have received these vaccines, however the vaccine may not be effective at preventing disease," Director of Public Health Mark Veitch said.

"It is not possible to determine whether vaccines administered at the clinic were effective or ineffective.

"Out of an abundance of caution, we are recommending people who received vaccines at the clinic to seek advice and consider having those vaccine doses repeated."

Vaccines that may be affected are those on the National Immunisation Program.

This includes routine government-funded childhood vaccines and some government-funded vaccines given to teenagers, adults and pregnant women.

The health department says flu and COVID-19 vaccines purchased from pharmacies on private scripts have not been affected.

Letters have been mailed to people impacted but due to record keeping over an extended time period, the current contact details of all those affected may not be known, the department says.

People who have been affected are encouraged to speak with their general practitioner to discuss revaccination relevant to their circumstances.

They can also visit the Department of Health website or call the public health hotline for more information.