MRC-5

MRC-5 (Medical Research Council cell strain 5) is a diploid cell culture line composed of fibroblasts, originally developed from the lung tissue of a 14-week-old aborted white male fetus.

[1][2] The cell line was isolated by J.P. Jacobs and colleagues in September 1966 from the seventh population doubling of the original strain, and MRC-5 cells themselves are known to reach senescence in around 45 population doublings.

[2][3][4] MRC-5 cells are currently used to produce several vaccines including for hepatitis A, varicella and polio.

[5] During the COVID-19 pandemic, anti-vaccination and anti-abortion activists believed that MRC-5 was an ingredient of the Oxford–AstraZeneca COVID-19 vaccine, citing a study from the University of Bristol.

David Matthews, a co-author for this study, clarified that MRC-5 was solely used for testing purposes to determine "how the Oxford vaccine behaves when it is inside a genetically normal human cell.