II In response to Prichard and Shipman's letter to the editor regarding the paper: Efficacy of ganciclovir in combination with zidovudine against cytomegalovirus in vitro and in vivo: Freitas, V.R., Fraser-Smith, E.B., Chiu, S., Michelson, S. and Schatzman, R.C. (1993) Antiviral Res. 21, 301–315