What should Krishner do? Does he accept the latest test results? Does he manufacture the vaccine based on the other three studies? What should he consider as he makes his decision?

Clinical trials are research studies that test the effectiveness of new drugs, equipment, vaccines, and medical procedures. Many of these trials are funded by private companies. Usually, these companies want to sell the medicines or equipment related to the study.
Changing or “fudging” data can be tempting for funding organizations when results of a lab experiment are unexpected or difficult to understand.
Ideally, clinical trials and tests from several sources would show similar results. If that is the case, the results are considered to be true, or valid.
Sometimes, though, studies show conflicting results.