BOSTON -- Three more measles cases have popped up at a business in the John Hancock Tower, bringing the total number of cases of the rarely-seen illness to seven in the Bay State.

NewsCenter 5's Pam Cross reported that the employer, Investors Bank and Trust, learned about the cases earlier this month when the Boston Health Department began an investigation into how the outbreak started.

"We were notified that 93 to 95 percent of the U.S. is immunized so, you don’t hear about it much, We don't think it will be much of a big deal and because of our population being so young, we think we are even higher in terms of a percent of those who are already immunized," said John Spinney, of Investors Bank & Trust.

The workers are all employees of Investors Bank and Trust and worked in two specific areas and came in contact with a contractor from India.

"Three were six employees and five of those are cleared to come back to work. We worked collectively with Boston Public Health and followed their instructions. We have vaccinated 600 people (Thursday). Hopefully, we will get the rest of our workforce vaccinated (Friday). We have asked our employees to get documentation of vaccinations as well, just to make the process work faster and keep it from spreading," Spinney said.

According to the Massachusetts Department of Public Health, other companies in the John Hancock Tower are being asked to take a more active role in determining the vaccination status of their employees. In addition, other educational materials related to respiratory and hand hygiene will be posted throughout the building.

Clusters of measles are rare, but health officials said the illness is a reminder for people to check if they are immunized against measles.

Another 1,000 to 1,200 employees of Investors Bank and Trust should be vaccinated by next week.