They usually track the lot numbers but I don't think it is for QA - https://cairnsnews.org/2018/11/19/u-s-govt-loses-landmark-vaccine-lawsuit
They also make sure to split and ship lots all over to attempt to hide 'hot lots' through geographical confusion. https://www.sott.net/article/396436-The-Tennessee-Sudden-Infant-Death-Syndrome-cluster-How-Wyeth-concealed-the-DPT-vaccine-SIDS-link
My mom sent me pics of my vaccine records (she wishes she had never vaccinated me or my brother at all but she believed the doctors up until I got so sick from them when I was a teen). There are no lot numbers but this would have been 1978,1980,and 1996. These are just handwritten documents from doctors to get into school.
They usually track the lot numbers but I don't think it is for QA - https://cairnsnews.org/2018/11/19/u-s-govt-loses-landmark-vaccine-lawsuit
They also make sure to split and ship lots all over to attempt to hide 'hot lots' through geographical confusion. https://www.sott.net/article/396436-The-Tennessee-Sudden-Infant-Death-Syndrome-cluster-How-Wyeth-concealed-the-DPT-vaccine-SIDS-link