Updated data from the Centers for Disease Control & Prevention now shows nine Massachusetts counties at either substantial or high risk for COVID-19 transmission, up from four counties last week.

The new data has the CDC advising that even more Bay State residents mask up indoors in public places, even if they're fully vaccinated.

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Massachusetts counties at high risk for transmission of the virus include Nantucket and Barnstable counties on Cape Cod during peak tourist season.

Information from the CDC showed Bristol and Suffolk counties at substantial risk last week, while this week Hampden, Worcester, Middlesex, Essex, and Plymouth counties were added.

In any county deemed a moderate risk, the CDC recommends that even fully vaccinated individuals wear masks when in public indoor settings.

Berkshire County remains at moderate risk as concern over a small outbreak of the Delta variant at North Adams Commons. The number climbed to 35 confirmed cases today, Monday, Aug. 2, with an overwhelming majority of cases among vaccinated people.