evidence: Safety of residual cellular DNA in vaccines [...] The risks, if any, of residual cellular DNA in vaccines as a result of the production process are theoretically two in number: (i) transmission of latent viruses and other agents; and (ii) incorporation of cellular DNA into host genetic material. These are theoretical safety issues that need to be considered in the scientific decisions underpinning registration of vaccines produced in new cell substrates. GACVS noted that WHO will be setting up a Working Group to consider international specifications for the quantity of residual cellular DNA in vaccines from new cell substrates. The Committee has agreed to serve as a reference point for safety issues for this Working Group.