A key indicator of a vaccination or medication's effectiveness in preventing or treating viral illnesses is its capacity to kill viruses. In most cases, the efficacy of the vaccine or medication to neutralize a virus can be assessed by incubating it directly with a live virus in vitro and observing how well the virus can infect cells. However, for the extremely contagious SARS-CoV-2, processes involving live viruses must be carried out under BSL-3 settings, which significantly restricts the COVID-19 vaccine and medication development process. Pseudoviruses lack the nucleic acid of the virus and are unable to multiply in the body despite possessing the proteins required for living viruses to infect cells.
For more: SARS-CoV-2 neutralization assay