Next events centred around establishing criteria for the karyology of these cells, which was thought to be very significant at that time. It was thought to be significant because of the worry that if the chromosome constitution of a normal cell changes after many subcultivations, as did happen in the later subcultivations of WI-38, that it would represent a threat and that it might appear to the genesis of a cancer cell population. That turned out not to be true, but there were a number of meetings held over the years to establish standards for chromosome analysis, which required the dedication of one or more individuals and pharmaceutical companies to do chromosome studies before the vaccine was released.

It is almost impossible to understand why chromosome standards were never set for monkey kidney or chicken cells; they were demanded of our human diploid cells. There are a number of other bizarre inconsistencies in the understanding of scientists in respect to what... needs to be approved and what doesn't have to be approved. The argument with the monkey cells was: well, we've been using monkey cells for so many years and there doesn't seem to be any cancer occurring in the recipients – and that's highly questionable because of SV40 – then they're safe. It was that kind of argument. Well, we had absolute proof that these cells weren't cancers because nobody in their right mind would inoculate primary monkey kidney cells into a terminal cancer patient, where we... in respect to what is possible to happen concerning unwanted viruses, dangerous viruses. But we had no trouble introducing normal human cells into cancer patients and... which we learned that there was no problem because it simply disappeared. And no one ever did that with primary monkey kidney cells. In any case, I don't want to belabour that point, but it's an essential point and had advocates on both sides for a number of years until the other side eventually collapsed.