Personal　protective　behaviors　and　their　dynamic　change　are　known　to　play　a　major　role　in　the　community　spread　of　severe　acute　respiratory　syndrome　coronavirus　2　(SARS-CoV-2),　the　causal　pathogen　of　the　coronavirus　disease　2019　(COVID-19)　pandemic.　In　this　study,　a　total　of　3229　students　in　Chinese　universities　completed　an　online　survey　about　their　knowledge　on　transmission　and　personal　protective　behavior　before　and　after　COVID19　vaccination.　Of　the　respondents,　87.6%　had　been　vaccinated.　Most　students　believed　that　the　large　droplet　(97.0%)　and　short-range　airborne　(89.3%)　routes　were　the　two　most　likely　SARS-CoV-2　transmission　routes,　whereas　only　24.1%　considered　long-range　airborne　transmission　to　be　possible.　Students　who　would　be　expected　to　possess　better　knowledge　about　virus　transmission　(e.g.,　students　of　medicine)　reported　better　personal　protective　behaviors.　Female　students　reported　relatively　better　personal　hygiene　practices　than　male　students,　so　did　the　confident　students　than　their　diffident　peers.　Students　washed　their　hands　on　average　of　5.76　times　per　day　during　the　pandemic.　Students　at　universities　in　southern　regions　washed　their　hands　more　frequently　but　paid　less　attention　to　indoor　ventilation　than　did　their　northern　counterparts.　Interestingly,　students　who　are　fear　of　being　infected　had　the　bad　personal　hygiene.　University　students　wore　22%　less　masks　in　public　indoor　environments　after　vaccination.　Chinese　university　students　weakened　their　personal　protective　behavior　after　vaccination　and　it　may　increase　the　potential　risk　of　infection　in　the　new　waves　of　variant　virus　(e.g.　delta).