It has been shown that IgM generated by pneumococcal polysaccharide vaccine is sufficient to confer protective immunity to Streptococcus pneumoniae (42); therefore, the use of O-glycan antigens on the cell surface or P. gingivalis OMVs for vaccine development for the prevention of P. gingivalis-related systemic diseases such as Alzheimer’s disease is worth further investigation. This evidence concerns the gene CD40LG and early-onset autosomal dominant Alzheimer disease.