LANSING (AP/WWJ) – Michigan health officials say vaccines are safe, and they’re emphasizing the need to keep children’s vaccinations up to date following recent chickenpox outbreaks.

The Michigan Department of Health and Human Services says Tuesday that outbreaks have been reported in recent weeks in Calhoun, Grand Traverse, Muskegon and Wayne counties and have involved mainly unvaccinated children in school settings.

READ MORE: Election Denial Probe Looms Over Critical Races In Michigan

Immunization against chickenpox and several other diseases is required for school entry in Michigan. However, parents have the option to waive the requirement.

WWJ’s Dr. Deanna Lites reports some of the affected children were hospitalized.

Also known as varicella, chickenpox is characterized by an itchy, blistery rash. The rash may be preceded or accompanied by fever, tiredness, headache and loss of appetite. Chickenpox is highly contagious, with the virus spreading through coughing and sneezing.

READ MORE: Police Search For Suspect In Fatal Shooting On Detroit's West Side

Studies have shown the recommended two-dose series given in childhood is somewhere between 89 percent and 98 percent effective in preventing any mild-to-moderate chickenpox disease and 100 percent effective in preventing severe chickenpox.

[Get more information from the state about vaccinations HERE].

TM and © Copyright 2015 CBS Radio Inc. and its relevant subsidiaries. CBS RADIO and EYE Logo TM and Copyright 2015 CBS Broadcasting Inc. Used under license. All Rights Reserved. This material may not be published, broadcast, rewritten, or redistributed. The Associated Press contributed to this report.

MORE NEWS: Amy Black, Who Was Sentenced To Life In Prison At 16, Granted Parole