好，介詞沒問題。我覺得你的提議和原標題在語法上都正確。我上網看了一下，不同的媒體在報道這則消息時用了略微不同的標題。我在

此把他們列出來，或許能幫助你理解。1，Student killed himself after bullying about his vaccination status. 2. Chicago teen committed suicide after ( relentless ) bullying about his vaccination status. 3. Latin School student died after ("increasingly cruel") bullying ignored by adults. 4. Student takes his own life after being bullied over his vaccination status. 5. Student kills himself after （peers mercilessly bully him ）over his vaccination status. 6. Chicago student died by suicide after bullying while school 'turned a blind eye'. 把例2 和例3 括號裏的修飾詞去掉，就跟例1一樣了。把例5裏的bully改成現在分詞，其它詞去掉，也跟例1一樣了。例4跟你的想法一致。所以，兩者語法上都對。原標題強調事件本身，用動名詞，使標題更簡捷。例4強調動作，用被動語態，意思更明了。對英語讀者來說，兩者都不會有太多誤解。