The pro and con commentaries by Drs Judelsohn and Katz (Pediatrics 1996;98:115-117) do not mention projected costs. In these days of limited resources, the greatest bang for the buck is important and perhaps is becoming the most important factor of delivery of medical services to large populations. Developing a single product multi-vaccine containing inactivated polio virus, to be followed by oral live virus vaccine, will unquestionably add to the cost of protection. Also, Dr Katz does not seem to address the problem of compliance.