A new manipulation of the vaccinia genome has been found to be an effective treatment of certain cancers. More specifically, researchers have deleted the F4L gene, which codes for the enzyme ribonucleotide reductase, and have now been able to produce a selective oncolytic-virus promoting anti-tumor immunity in bladder cancers. Regarding cancer therapies, viral vectors are among some of the safest due to the low prevalence of side effects or secondary interactions when compared to something like chemotherapy which lacks the precision in cell killing or surgery which lacks the broad-spectrum applicability. Further studies with this manipulated virus strongly support the original correlational claim when observing successful results in both ex vivo cultures and mouse models. A virus of historical significance is still influencing the treatment of deadly diseases in the modern era, but will it have as great an impact as it did in the past?