among cytomegaloviruses, it has not been determined if a single prototype virus, such as AD 169, can protect against strains of somewhat differ¬ ent antigenic composition.Both Weiler16 and Dudgeon17 have considered the problems involved in the development of a cytomegalovirus vaccine and cautioned against the use of a live virus. Dudgeon suggests that the possibility of an inactivated vac¬ cine with adjuvant deserves consid¬ eration because of the persistence of the live virus and the durable immu¬ nity produced by inactivated poliovirus vaccines. It should be pointed out that irrespective of the viability of the product, it is highly desirable to administer a cell-free vaccine rather than a lysate. Methods are now avail¬ able for the production of a high-titered, extra-cellular virus that would eliminate any possibility of adverse effects from cellular contamination.18The above notwithstanding, the preliminary work by Elek and Stern will almost certainly be followed by similar investigations elsewhere. Al¬ though it is too early to predict what the outcome will be, it seems quite certain that we are going to hear a good deal of spirited debate on the subject of cytomegalovirus vaccines. This is appropriate. After all, has this not been true for every vaccine devel-oped since Edward Jenner inoculated 8-year-old James Phipps with pus from a cowpox lesion?