Rapid and accurate determination of the potency of varicella vaccine by quantitative polymerase chain reaction

► The potency of varicella vaccines is currently determined by a plaque assay, which is laborious and has considerable inter- and intra-assay variability. ► The increasing demand for varicella vaccine requires a rapid, reliable assay to facilitate the availability of the vaccine. ► A new potency assay for varicella vaccine based on quantitative polymerase chain reaction in conjunction with a much more efficient virus infection step is described. ► The new assay is much faster and possesses high-throughput capacity in addition to acceptable accuracy and reproducibility when compared with the plaque assay. ► Using 23 vaccine lots from 7 manufacturers, we found no significant difference in infectivity between the new assay and plaque assay, suggesting that the assay could potentially be a viable alternative for vaccine analyses.