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Table 3 Safety concerns of the vaccine strain

From: Live bacterial vaccines – a review and identification of potential hazards

Systemic disturbance Systemic infection
  Conversion from avirulent to virulent bacterium
  Translocation to organs
  Disturbance of digestive processes
  Inhibition of bacterial production of nutrients
Immune system Absorption of allergens through the intestinal epithelium
  Induction of tolerance to pathogen instead of immunity
  Induction or potentiation of autoimmunity
  Bacterial mimicry of self-antigen
Metabolites Production of harmful/undesired metabolites including enzymatic activities
  Breakdown of chemicals to toxic metabolites
Implications for natural flora in GI tract Permanent colonisation of cell substrate in the intestine
  Gene/plasmid transfer to host's indigenous flora
  "Competitive exclusion" of indigenous flora
Unintentional transferral of cell substrate Unintentional transfer to other individuals
  Unintentional transfer to and viability/propagation in environments other than the intestines
Contamination Extraneous or perceived adventitious DNA components should be removed (possibility of oncogenicity).