Master and Working Seed Banks are produced by the manufacturer from the supplied parent strain in Specific Pathogen Free (SPF) eggs, which are tested for confirmation of viral genome stability and absence of contamination.

To produce inactivated influenza vaccines on a large scale, the use of SPF eggs is not a viable option and so high quality “production” eggs are obtained from accredited flocks certified to rigorous quality control standards. The eggs are brought on site using temperature-controlled vehicles, cleaned and sanitised before being set at a holding temperature. Eggs are then incubated for 10-11 days before inoculation with the Working Seed Virus. A small volume of the Seed is injected either manually or through dedicated automated machinery into the allantoic cavity of the egg. The eggs are then incubated at 35-37oC at a relative humidity of around 65% for 48 to 72 hours to allow the virus to multiply.