“Well, they left it in the polio vax deliberately. They knew it was there but didn’t want to spend time and money refining it out.”
In Conspiracy World everything is done deliberately.
That used to be the province of leftists who explained everything by invoking Corporate Greed, but in our current era the koolaid gets served by both sides.
In the real world not inhabited by conspiracy nuts, SV40 was hard to detect until the advent of PCR testing in 1983.
SV40 contamination in the 50s and 60s became known once polymerase chain reaction tests were able to be run on samples of early Salk and Sabin vaccines.
People who worked on the vaccine knew it was in there, they didn’t want to spend time and money to take it out. The teams denied it was even in there publicly or that it could even cause cancer.
Independent folks knew by 1960 it was there yet because the makers denied it they kept giving those vaccines to people at least into 1963.
So they could have stopped injecting people with sv-40 contaminated vaccine and did not.
https://www.the-scientist.com/news-analysis/sv40-in-vaccines-53009