smolaw11/iStock By ANNE FLAHERTY and SOPHIE TATUM, ABC News (WASHINGTON) — While teachers unions and school systems clash over what is considered a safe return to in-person learning and President Joe Biden looks to reopen a majority of K-8 schools in 100 days, the head of the Centers for Disease Control and Prevention said Wednesday it could be possible to get back to school safely without hinging the return to classrooms on vaccines. “There is increasing data to suggest that schools can safely reopen and that safe reopening does not suggest that teachers need to be vaccinated in order to reopen safely,” CDC Director Rochelle Walensky told reporters at a briefing. “Vaccination of teachers is not a prerequisite for the safe reopening of schools.”