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Why is it necessary to stop OPV use in
routine immunization programmes, after the eradication of wild
poliovirus?
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When will OPV cessation occur?
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Where will OPV cessation occur?
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How was international consensus attained for OPV cessation?
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What do countries which currently use OPV need to do to prepare for OPV cessation?
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What do countries which currently use IPV need to do to prepare for OPV cessation?
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Why does OPV cessation need to occur in an internationally-simultaneous way?
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How can countries ensure high population immunity levels, following OPV cessation?
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What happens if an outbreak of polio occurs, following OPV cessation?
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Why is the World Health Organization (WHO) not recommending universal introduction of inactivated polio vaccine
(IPV)?
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What will be the role of IPV following OPV cessation?
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Who will be responsible for the management, maintenance, financing and - if necessary - replenishment, of the OPV stockpile?
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Will countries be allowed to keep their own stockpile?
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How will containment be verified and monitored?
1. Why is it necessary to stop OPV use in
routine immunization programmes, after the eradication of wild
poliovirus?
A. After interruption of wild poliovirus globally,
the Sabin strains contained in OPV will be the only source of live
polioviruses in the community. OPV, in rare instances, can cause
vaccine-associated paralytic poliomyelitis (VAPP). In
addition, the Sabin strains can mutate back to greater
neurovirulence and transmissibility, establish endemic and
epidemic transmission, and thus pose a threat to eradication. The
continued use of OPV after the interruption of transmission of
wild poliovirus is therefore increasingly considered inconsistent
with eradication. Polio cases– due to vaccine-associated
paralytic poliomyelitis (VAPP)– and outbreaks– due to
circulating vaccine-derived polioviruses (cVDPVs)– are the two
main reasons for eventually stopping the use of OPV for
routine immunization in all countries.
In September 2004, the Advisory Committee on
Poliomyelitis Eradication (ACPE) confirmed that "after
eradication of wild poliovirus, continued use of OPV would
compromise the goal of a polio-free world."
Once wild poliovirus is no longer circulating
in the environment and transmission has been interrupted, the
public health benefits of routine immunization with OPV will no
longer outweigh the burden of disease presented by VAPP and cVDPVs.
In addition, the threat of infection from a Vaccine-derived
Poliovirus, caused by the reintroduction of attenuated
polioviruses of OPV, will be greater than the threat of wild
poliovirus infection.
2. When will OPV cessation occur?
A. OPV Cessation should occur as soon as possible
after interruption of wild poliovirus transmission at a time when
surveillance sensitivity is high, but only after certification of
wild poliovirus eradication. The effective implementation of
the six prerequisites for simultaneous OPV cessation would have to
be ensured. These prerequisites are:
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confirmation of interruption of wild poliovirus transmission
globally and appropriate bio-containment of wild polioviruses;
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maintenance of the global surveillance and notification capacity;
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establishment of a global stockpile of mOPVs and a global response
mechanism;
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implementation of IPV requirements in countries that retain
poliovirus for research and/or vaccine production;
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synchronization of OPV cessation globally, and
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appropriate bio-containment of Sabin polioviruses.
The timetable for OPV cessation can divided
into three distinct periods correlating with the evolution of the
major polio risks and risk management strategies. These are:
The precise timing of these phases will depend
on the date of interruption of wild poliovirus transmission
globally and progress towards achieving the six prerequisites for
OPV cessation.
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3. Where will OPV cessation occur?
A. In order to ensure that no country is
inadvertently put at risk of importing a cVDPV from a country that
continues to use OPV, the cessation of OPV use for routine
immunization would have to occur in a synchronous simultaneous
manner, world-wide. No country should be permitted to
continue using OPV after this has occurred, because it will put
all other countries at risk.
4. How was international consensus attained for
OPV cessation?
A. The international bodies providing oversight to
the Global Polio Eradication Initiative have endorsed the need for
eventual simultaneous OPV cessation. An eventual World Health
Assembly Resolution will be necessary confirming international
consensus to cease using OPV following the eradication of polio.
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5. What do countries which currently use OPV need
to do to prepare for OPV cessation?
A. WHO has begun the process of developing and
pilot testing guidelines for the withdrawal of OPV from routine
immunization programmes. These guidelines will emphasize the need
to maintain the highest-possible level of OPV coverage and AFP
surveillance until the actual time of simultaneous OPV cessation.
It will be essential that all countries
currently using OPV develop a well-defined immunization policy for
implementation following OPV Cessation. Among the options
available will be the continuation of immunization against polio
through the use of the Inactivated Polio Vaccine (IPV).
6. What do countries which currently use IPV need to do to prepare
for OPV cessation?
A. Countries currently using Inactivated
Poliovirus Vaccine (IPV) will have to confirm whether they intend
to maintain their polio immunization policies. In addition,
these countries must also ensure that they meet the containment
requirements established for the OPV cessation and verification
phase and the Post OPV era.
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7. Why does OPV cessation need to occur in an
internationally-simultaneous way?
A. Due to the proven risk of exportation of a
virus from one country to another, the use of OPV following the
interruption of wild poliovirus transmission will constitute an
international public health risk. In order to avoid some
countries becoming more vulnerable to infection by a VDPV than
others, it is essential that all countries cease using OPV at the
same time.
8. How can countries ensure high population
immunity levels, following OPV cessation?
A. Countries will have to determine for themselves
which will be the most appropriate immunization policy to
implement following OPV cessation, based on their perceived risks
of infection. The two options currently available are either
to stop all polio vaccination or to switch to IPV. A 2-dose IPV
schedule may provide adequate population immunity. Research has
been on-going in the development of new vaccines such as Sabin IPV,
which may soon provide additional options for protection against
polio. A supplement to the WHO position paper on the Introduction
of IPV into OPV-using countries was recently published in the WER
addressing the policy decisions necessary for the OPV Cessation
era and the implications on immunity.
There are also key risk management strategies
that may be implemented to protect populations and minimize the
risk of an inadvertent release or reintroduction of poliovirus.
These include the reduction of the number of facilities storing or
handling polioviruses and the implementation of high-level
bio-containment.
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9.
What happens if an outbreak of polio occurs, following OPV
cessation?
A. An internationally managed global stockpile of
monovalent OPV (types 1, 2 and 3) is being developed for use in
the event of a polio outbreak after the cessation of OPV. Such a stockpile will allow a type-specific response which will
not only ensure a greater impact of the outbreak response, but
also prevent the reintroduction of other polioviruses.
The Global Polio Eradication Initiative is also
considering the potential role of IPV and antivirals in an
outbreak response.
10. Why is the World Health Organization (WHO) not recommending
universal introduction of inactivated polio vaccine (IPV)?
A. In countries without poliovirus storage or IPV
production, OPV cessation will be primarily associated with a time
limited risk of paralytic disease due to the potential emergence
of circulating vaccine-derived poliovirus (cVDPV) (e.g., 3-5 years
after OPV cessation). Based on the experience in cVDPV management
in the past 5 years, this risk can be efficiently and effectively
managed with an mOPV stockpile to which all countries would have
access. Consequently, WHO will not recommend universal IPV due to
the very high actual and opportunity costs.
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11. What will be the role of IPV following OPV
cessation?
A. As stated above, IPV is currently the only
option for countries wishing to continue routine polio
immunization. Countries which perceive themselves to be at risk
for wild poliovirus release/re-introduction may decide to
introduce IPV.
12. Who will be responsible for the management,
maintenance, financing and - if necessary - replenishment, of the
OPV stockpile?
A. The management of the polio vaccine stockpile
will take advantage of existing governance mechanisms which will
not only ensure a well-functioning and cost-effective
administration, but provide countries a familiar platform of
operation. WHO will act as the managing agency for the polio
stockpile, while UNICEF will be responsible for procurement and
storage processes. The ACPE would assume responsibility for
decision-making concerning trigger mechanisms in the event of a
polio outbreak in the Post-OPV era, including the drafting and
approving of SOPs for a trigger of stockpile vaccine release. By
the start of the Post-OPV phase, the control of the stockpile
would have fully shifted within WHO, from the Polio Eradication
Initiative (POL) team to the Alert and Response Operations (ARO)
team.
The financing of the stockpile has been secured
via GAVI by the International Finance Facility for Immunization.
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13. Will countries be allowed to keep their own
stockpile?
A. International agreement will be sought through
a WHA resolution ensuring that the global polio vaccine stockpile
managed by WHO will be the only OPV stockpile and countries will
not keep their own.
14. How will containment be verified and monitored?
A. Countries must conduct an in-depth survey for
wild- and vaccine-derived poliovirus infectious materials, among
all research and diagnostic laboratories. The requirements
for laboratories which decide to hold poliovirus will become more
stringent. This process must be finalized by the time wild
poliovirus transmission is interrupted globally, and the process
of destroying or properly containing those materials must be
completed 12 months later. Specific policies will be
published in a 3rd edition of the Global Action Plan for
Laboratory Containment (GAP III).
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