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bacterial conc.Control of bacterial count is essential.

Virus vaccines

Virus strain used for vaccine production

Killed virus vaccine ---killed in a regular manner, shall be

Immunogenic.

Critical amount of formalin to kill the virus and retain its
antigenicity .The most immunogenic strain of the virus is
selected(Influenza ).The composition of influenza vaccines is
constantly under review.

For poliomyelitis isolated wild virus attenuated in cell
culture

(e.g. monkey kidney tissue incubated at 35 C was
used),chick

embryo fibroblast cultures were used to attenuate measles

virus.Small pilot clinical trials to test reactivity in man
followed

by larger trials to prove safety and immunogenicity and

general acceptability when used on a large scale.It is
essential

to ensure that the attenuated strain has not reversed to
the wild strain,and to ensure that the strain has not further

become attenuated and become less immunogenic.

Tests on cell substrate

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