About the Authors

Sarah Knowlson

Affiliation Division of Virology, National Institute for Biological Standards and Control, Potters Bar, Hertfordshire, United Kingdom

John Burlison

Affiliation Division of Virology, National Institute for Biological Standards and Control, Potters Bar, Hertfordshire, United Kingdom

Elaine Giles

Affiliation Division of Virology, National Institute for Biological Standards and Control, Potters Bar, Hertfordshire, United Kingdom

Helen Fox

Affiliation Division of Virology, National Institute for Biological Standards and Control, Potters Bar, Hertfordshire, United Kingdom

Andrew J. Macadam

Affiliation Division of Virology, National Institute for Biological Standards and Control, Potters Bar, Hertfordshire, United Kingdom

Philip D. Minor

Philip.Minor@nibsc.org

Affiliation Division of Virology, National Institute for Biological Standards and Control, Potters Bar, Hertfordshire, United Kingdom

Competing Interests

The authors have declared that no competing interests exist.

Author Contributions

Conceived and designed the experiments: SK JB EG HF AJM PDM. Performed the experiments: SK JB EG HF. Analyzed the data: AJM PDM. Wrote the paper: PDM AJM.