Office providers in the Twin Cities may have to wait a few more months to see their spaces fill up with warm bodies as businesses take a wait-and-see approach to bringing employees back to their cubicles. In a new report, Colliers International’s Minneapolis-St. Paul office said many companies won’t start to implement long-term “return-to-work” plans until after Labor Day. By that time, youngsters will be back in school after summer break and more will be known about the effectiveness of the COVID-19 vaccine, the report says. School schedules and vaccine efficacy are among the factors that employers will consider before allowing workers to leave their home offices for traditional corporate work spaces, according to the Colliers first-quarter office report.