BOSTON -- Local school staffers who were supposed to be vaccinated against the H1N1 flu were mistakenly given a dose of insulin instead, NewsCenter 5 has learned.

NewsCenter 5's Rhondella Richardson reported that several staffers at Wellesley's Schofield School got insulin shots during a flu shot clinic at the school on Friday.

Somehow six staffers mistakenly received a shot of insulin, not the vaccine, the school said.

Although the vaccine was dropped off at the school by the Wellesley Department of Health, health officials said the insulin was not shipped with the vaccines, adding the department doesn't even have access to insulin.

Some faculty members who got the incorrect shot got sick.

On Sunday, Wellesley Superintendent of Schools Bella Wong sent a note home to parents and faculty saying: "These staff were cautioned to report to a medical facility to be monitored for necessary support at any sign of symptoms that a drop in blood sugar would cause. It is, without a doubt, most fortunate that any impacted staff that did receive insulin in error did not come to greater harm as might have happened when they became ill."

Hypoglycemia, or low blood sugar, can be dangerous for anyone who has extra insulin when they don't need it for medical reasons, experts said.

A full investigation is under way.