WEBVTT

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AHMAD OMID RAHIMI:
Now let's begin.

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Oral Polio Vaccine or OPV is
a still the main preventive

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measure against polio
which is taken orally

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as drops, easily administered
and does not require a trained

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health worker.

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However, in
extremely rare cases,

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OPV can lead to
paralysis itself.

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If no mutation has occurred,
there is a 1 in 750,000 to 1

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and 2.7 million chance
in every polio drug

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to cause paralysis with no risk
of a spread to other children.

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This is called
vaccine-associated polio

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paralysis.

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In addition to that,
sometimes a very rare strain

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or type of virus,
which has mutated

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or genetically changed
from the original strain

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can cause paralysis.

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This virus is called
vaccine-derived polio virus.

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And if this leads to an outbreak
more often in low vaccination

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coverage areas, it's
called circulating

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vaccine-derived
polio virus or CVDPV.

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It's noteworthy that the amount
of paralysis caused by the OPV

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is a small fraction of
that amount of paralysis

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that would exist, but this
vaccine associated paralysis

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is an important reason that why
once polio has been eradicated,

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we should stop using
oral polio vaccine

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and rely entirely on IPV or
Inactivated Polio Vaccine.

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The first major outbreak of
paralysis caused by CVDPV

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occurred in 2000 and
2001 in the island

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of Hispaniola, an island
in the Caribbean Sea

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that includes the countries of
Haiti and Dominican Republic,

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where low routine
human immunization

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rates against polio
allowed circulating

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vaccine-derived polio
virus to spread.

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This figures shows a
geographic distribution

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of the biologically confirmed
cases, which are represented

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by circles and polio
compatible cases,

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represented by stars
associated with type 1

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circulating vaccine-derived
polio virus.

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Outbreak is in Hispaniola.

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Environmental samples that
were positive for type 1

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CVDPV isolates are
represented by triangles.

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And now this is
a short animation

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about CVDPV with its link
provided in this presentation.

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This is a very concise video
about the vaccine-derived polio

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vaccine.

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And in summary, it says
that if immunity is high,

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vaccine-derived
virus cannot arise.

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That's why it's so
important to reach

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every last child with vaccines.

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And now we are going to talk
about new tools and strategies

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aiming to reduce the risk of
vaccine-derived polio virus.

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Over all, we have
two strategies.

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One is switching from
trivalent oral polio vaccine

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to bivalent oral polio vaccine.

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And the other is administering
the inactivated polio vaccine

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or IPV.

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Trivalent OPV or tOPV protects
against all three types

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of polio viruses, type
1, type 11, and type III.

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Bivalent oral polio
vaccine or B OPV

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targets type I and type
III, but not type 2.

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Wild virus type 2
has been eradicated,

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but this is now circulating
type 2 vaccine-derived polio

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vaccine across the world.

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To try to stop this
from happening,

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there was a switch to bivalent
polio vaccine which contains

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only type I and type III.

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However, the tricky thing is
that while bivalent vaccine

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cannot cause type 2 circulating
vaccine-derived polio virus,

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it also can not to stop
circulation of type 2 vaccine

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derived polio vaccine.

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IPV or inactivated
polio vaccine also

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protects against all three
types of polio viruses.

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Until a few years
ago, IPV was not

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used at all and
much of the world,

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but recently IPV
has been introduced

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into routine and immunization
systems globally.

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Inactivated polio vaccine also
protects against all three

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types of polio viruses.

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Until a few years ago,
IPV was not used at all

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in much of the world.

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But recently, IPV has been
introduced into routine

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immunization systems globally,
because it cannot cause

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circulating vaccine-derived
polio vaccine and provides

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immunity to all three
types of polio virus.

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However, OPV or
oral polio vaccine

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is still an important
tool used in campaigns

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as it is easily administered
and does not require a trained

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health worker and most
importantly, provides

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environmental immunity
that IPV is not capable of.

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And now here's a short
glossary of some common polio

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related abbreviations that you
might encounter in this module.

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To wrap it up in
these few slides

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we found out that
oral polio vaccine

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is a very important tool
for polio eradication.

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However, it causes circulating
vaccine-derived polio virus,

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which has a side effect
of this kind of vaccine,

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but we have to still
rely on OPV to cover

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and to reach every child
throughout the world

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and increase the immunity of
these children against OPV.

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Once we reach to our target,
then we can shift to IPV.

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And once IPV is part of the
routine in every country,

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then we wont have any
cases of circulating

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vaccine-derived polio virus.

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