Customers may have been exposed to hepatitis A at a Farmingdale restaurant.
Officials say a worker at the Italian restaurant Trento on Route 110 may have spread the illness to customers.
The Suffolk County Department of Health Services says people at risk include anyone who had a beverage inside the establishment on July 19, 23, 26, 29 or 30.
The Health Department is offering free vaccines at their facility at 3500 Sunrise Highway, building 200 on Satuday fro 10 a.m. to 4 p.m.
Hepatitis A symptoms include abdominal pain, nausea, vomiting and diarrhea.
The restaurant's owner said, "I hope my customers understand we try to do our best, our restaurant is safe. I wouldn't allow anyone to come here if it wouldn't be safe because my reputation is important to me and I work very hard for all my staff."
The virus affects the liver and is usually transmitted by contaminated food and water.