Embryonated chicken eggs and primary chicken embryonic fibroblasts (CEF) have been used since decades for the manufacturing of human and veterinary viral vaccines, including traditional large volume vaccines such as human influenza or Newcastle disease vaccines, as well as more modern recombinant viral vectors (e.g. poxviruses).
They are the original single-use bioreactors inexpensive, easily scalable, and environmentally friendly. While long-standing, the process of egg based vaccine production has evolved to address various challenges, including yield, automation, capacity, quality assurance and production speed. Improvements to egg supply variability have also been made. In a typical egg based vaccine production, the eggshell is cracked, and the influenza virus is injected into the fluid surrounding the embryo. The egg is resealed, the embryo becomes infected, and the resulting virus is then harvested, purified and used to produce the vaccine.