Table 3.

Estimations of viral log₁₀ infectious units/ml at each stage of the manufacturing process from initial isolate to a final trivalent influenza vaccine (assuming worst-case conditions)

Process step	Influenza	Adenovirus	Parainfluenza	BK polyomavirus	Avian reovirus
Throat sample	7.0	7.0	7.0	7.0	n/a
Egg isolate and passages	8.0	8.0	8.0	6.0	8.0
MDCK viral seed passages	9.0	4.0a	7.9	4.0a	6.8
PCR-tested seed	9.0b	2.0c	3.0c	2.0c	6.8b
Bioreactor inoculum	6.0	−1.0	0.0	−1.0	3.8
Bioreactor harvest	9.0	−1.0	3.0a	−1.0	6.0
Chromatographies I and II	8.5	−1.5	2.5	−1.5	5.5
Concentration	9.7	−0.3	3.7	−0.3	6.7
BPL inactivation	−7.8	−2.8	−5.8	−2.4	0.3
Splitting/subunit purification	−13.6	−7.6	−11.6	−7.2	−7.4
Formulation/final product	−13.9	−7.9	−11.9	−7.6	−7.7
Human infectious dose per vaccine dose	−15.9	−9.9	−13.9	−9.5	−9.7

BPL, β-propiolactone; MDCK, Madin–Darby canine kidney; PCR, polymerase chain reaction.

^aNo viral growth, but assume contamination by human operators during the final-stage passage in MDCK 33016 cell culture.

^bPCR test not included in calculation, therefore the residual titre calculated in the previous step is maintained.

^cPCR detection limit applied at this step.