Personal information of nearly 500 seniors who received flu shots in Wellesley has been lost or stolen.
The information was in an envelope that had been mailed earlier this month by the town's health department to a Medicare office in Boston. But officials say when the envelope arrived, it was open and the contents were missing.
The Postal Service is trying to determine whether theft or mechanical failure was to blame.
The material included social security numbers, addresses and dates of birth for about 480 Wellesley seniors who had received flu shots from the town last fall.
The town is sending a letter to the seniors notifying them that their personal information may have been compromised.