Inactivated Polio Vaccine (IPV)
Comprehensive technical module
Rationale for IPV introduction & OPV withdrawal
in relation to Objective 2 of The Polio
Eradication & Endgame Strategic Plan
Immunization Systems Management Group (IMG)
Version date: February 10, 2014
Glossary of terms & abbreviations

cVDPV
Circulating Vaccine-Derived Poliovirus

DTP3
Diphtheria Tetanus Pertussis (third dose)

GPEI
Global Polio Eradication Initiative

IMG
Immunization Systems Management Group

IPV
Inactivated Polio Vaccine

OPV
Oral polio vaccine
-
bOPV
(bivalent, contains types 1 and 3)
mOPV
(monovalent)
OPV1
(type 1 component of OPV)
OPV2
(type 2 component of OPV)
OPV3
(type 3 component of OPV)

SAGE
Strategic Advisory Group of Experts on Immunization

VAPP
Vaccine-associated paralytic poliomyelitis

VDPV
Vaccine-derived poliovirus

WHA
World Health Assembly

WHO
World Health Organization

WPV
Wild poliovirus
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Definitions
Technical term
Definition (in the context of these slides)
Fractional Dose
A fractional dose is a dose that uses less antigen (1/5th or 1/3rd) for cost or supply sparing measures. With
IPV, fractional doses are being evaluated by administration into the skin (intradermal, ID). In contrast, full
dose is usually administered into the muscle (intramuscular, IM) or subcutaneous tissue (SC or SQ).
Intestinal
Immunity
Intestinal shedding refers to the amount of virus an infected person “sheds” or passes on through their
intestine (and fecal matter). Wild polioviruses and vaccine viruses can be spread from person to person this
way, if there is no intestinal immunity. In developing countries the major mode of transmission is thought to
be fecal shedding to others with oral ingestion.
Oral-pharyngeal
shedding
Oral-pharyngeal shedding refers to the amount of virus an infected person “sheds” or passes on through
their oral secretions (nose and mouth). In industrialized countries the major mode of transmission is thought
to be oral secretion to oral ingestion.
Priming
Children who do not seroconvert after a first dose are considered primed if they seroconvert within 7 days
of a 2nd dose.
Seroconversion
Seroconversion is defined as the development of antibodies in blood serum as a result of infection or
immunization and is correlated with protection
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Objectives of this module
1. Provide Technical background on Polio & Polio vaccines as it relates to
Objective 2 of GPEI’s Polio Eradication & Endgame Strategic Plan
-
Review Rationale for OPV cessation
Review Rationale for IPV introduction
2. Review of SAGE recommendations for IPV introduction
Note: this is a comprehensive stand-alone deck
of slides with an accompanying document
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Key messages for IPV introduction & OPV cessation
IPV recommended by
SAGE
• All countries introduce at least one dose of IPV into the
routine immunization system before the tOPV-bOPV switch
OPV cessation crucial
• OPV cessation must occur for the world to be polio free
because OPV in rare cases can cause paralytic disease
OPV cessation--2 phases
• Removal of type 2 in 2016 (tOPV to bOPV switch globally)
• bOPV cessation in 2018-2019 (complete cessation of
OPV)
IPV rationale
• Ensures that a substantial proportion of the population is
protected against type 2 polio after OPV2 cessation
Added IPV benefits
• Mitigates risks of type 2 reintroduction in association with
OPV2 cessation & facilitates polio eradication by boosting
immunity to types 1&3
IPV clarifications
• Recommended for routine immunization…not campaigns
• Recommended in addition to OPV…not replacing any OPV
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GPEI Accomplishment: Significant Decline in Polio-paralyzed
Children, 1988-2013*
400
1800
1600
1400
1200
1000
800
600
400
200
0
1352
Polio cases
Polio cases (thousands)
300
1604
200
650
369
230
2009
2010
2011
2012
2013
100
2013
2012
2011
2010
2009
2008
2007
2006
2005
2004
2003
2002
2001
2000
1999
1998
1997
1996
1995
1994
1993
1992
1991
1990
1989
1988
0
*as of 31 December 2013
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As wild polioviruses are eradicated, number of vaccine-derived cases
exceeds wild poliovirus cases
1800
Wild poliovirus cases
1604
1600
Vaccine-derived poliovirus
cases (VDPVs)/VAPP
1352
1400
Polio cases
1200
1000
800
650
600
369
400
230
200
?
?
0
0
0
0
2014
2015
2016
2017
2018
0
2009
2010
2011
2012
2013
Post interruption of WPV
transmission
A hypothetical scenario of estimated VDPV cases compared to reported
cases of wild poliovirus (as of 31 December, 2013)
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The Polio Eradication & Endgame Strategic Plan 2013-2018
The Plan differs from
previous eradication
plans
“complete the eradication
and containment of all
wild, vaccine-related, and
Sabin polioviruses such
that no child ever again
suffers paralytic
poliomyelitis.”
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The Plan has four objectives
1
• Detect and interrupt all poliovirus transmission
2
• Strengthen immunization systems, withdraw oral polio
vaccines (OPV), and introduce inactivated polio vaccine (IPV)
3
• Contain poliovirus and certify interruption of transmission
4
• Plan polio’s legacy
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Objective 2 of The Plan addresses the Endgame through
three distinct stages
2019-2020
2016
Withdrawal
Before
end 2015
Switch
• of bOPV & routine OPV
use
• tOPV to bOPV
Introduction
• at least one dose of IPV
• into routine immunization
Ongoing STRENGTHENING of routine immunization services
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Timeline for implementation of Objective 2, the Endgame
Last wild polio
case
Anticipated
timeline
2013
2014
2015
Phase in IPV
tOPV-bOPV
switch
2016
2017
Global
certification
Stop
bOPV
2018
2019-2020
IPV in routine immunization
 Before end of 2015: introduce one dose of IPV in immunization programs of all
countries, prior to tOPV-bOPV switch
 2016: tOPV-bOPV switch globally
 2019-2020: withdrawal of bOPV after the world is certified polio-free in 2018
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Technical Rationale for Oral Polio Vaccine (OPV) Cessation
Key Messages
 Because OPV in rare cases can cause paralytic disease, OPV
cessation must occur for the world to be polio free.
 OPV cessation will occur globally in two phases:
- removal of type 2 component (switch from tOPV to
bOPV) in 2016
- followed by bOPV withdrawal and cessation of OPV use
in 2018-2019.
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Oral Polio Vaccines (OPV) in routine and supplementary
immunization activities globally
 Types of OPV
-
Trivalent OPV (tOPV): types 1, 2, and 3
Bivalent OPV (bOPV): types 1 and 3
Monovalent OPV (mOPV): types 1 or 2 or 3
 Currently, TRIVALENT is the most commonly used OPV in routine
immunization globally, while BIVALENT is more commonly used in
supplementary immunization activities.
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Types of polioviruses
OPV
related
Wild
VAPP**
VDPVs*
•
•
•
•
99% reduction in cases of wild poliovirus since 1988
Type 1 (341 cases as of 20 November 2013†)
Type 2 (eliminated worldwide in 1999)
Type 3 (none detected since November 2012)
• Vaccine-associated paralytic poliomyelitis (VAPP)**
• Estimated ~250-500 globally per year
• Type 2 accounts for about 40% of VAPP
•
•
•
•
Vaccine derived polioviruses (VDPV)
Most are circulating VDPVs (cVDPVs)*
~49-184 per year since 2008 (through 20 Nov 2013)
Type 2 cVDPVs account for 97% of cVDPVs
† More up-to-date numbers can be found at http://www.polioeradication.org/Dataandmonitoring/Poliothisweek.aspx
*Other extremely rare VDPVs include primary immunodeficiency VDPVs (iVDPVs) and ambiguous VDPVs (aVDPVs)
**Refers to spontaneous reversion to neurovirulence of one of the attenuated viruses in OPV. VAPP occurs in OPV recipients or
their close contacts in contrast to cVDPVs which are widely transmitted in a community and are not likely to be related to contact
with a recent vaccine recipient.
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What does it mean for the world to be polio-free?
 Complete interruption of transmission and elimination of all polio disease
-
Wild polioviruses
Vaccine-derived polioviruses (VDPVs)
Vaccine-associated paralytic poliomyelitis (VAPP)
 Eradication & Endgame Strategic Plan 2013-2028 refers to both wild and
vaccine-derived polioviruses
Eradication
• Plan refers to wild
virus
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Endgame
• Plan refers to
management of
VDPVs and VAPP
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Rationale for continuing use of OPV until Polio Eradication &
Global Certification
Wild poliovirus
still circulating
• As long as there are susceptible persons in other countries,
there is risk of export of the virus to these countries.”
• Endemic in 3 countries – reservoirs for re-infecting others
(Pakistan, Afghanistan, Nigeria)
• In 2013, polio cases in 5 other countries previously polio free
countries (Somalia, Kenya, Ethiopia, Cameroon, Syria)
Eradication
requires OPV
• OPV is a critical component of the eradication strategy
until polio transmission is interrupted globally & the world is
certified polio-free,
• Risk of polio spread into other regions of the world is real
without the continued use of OPV
OPV is
appropriate for
eradication
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• Inexpensive
• Easy to administer
• Offers good oral and intestinal immunity—needed for
interruption of person to person transmission
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OPV withdrawal
Objective 2 of the Plan calls for a phased withdrawal and
containment of OPV globally
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Type
2
All
OPV
Phase 1
2016
Phase 2
2019-2020
Remove type 2 by switch from
tOPV to bOPV…
…followed by bOPV withdrawal
and cessation of OPV use in
2019-2020
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Rationale for removing type 2 component of OPV (OPV2)
 Risks of OPV2 far outweigh the benefits
-
Thus, need to remove OPV2, but need to maintain population immunity against type 2
with IPV prior to OPV2 cessation
 Type 2 poliovirus apparently eradicated since 1999 (last case detected
in Aligarh, India)
 New diagnostics and experience suggest that type 2 cause >95% of
cVDPVs
 Type 2 causes 40% of VAPP today
 Type 2 component of OPV interferes with immune response to types 1
and types 3
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Rationale for retaining Types 1 & Types 3 components of OPV
(bivalent OPV) until global certification of polio eradication
 Type 1 causes all polio cases related to wild virus today
-
Few VDPV cases are type 1
Few VAPP cases in immunocompetent individuals
 Type 3 last detected in November, 2012 (as of 20 November 2013)
-
Few VDPV cases are type 3
Most VAPP cases (60%) in immunocompetent persons are type 3
While lack of detection since November 2012 is promising, the period
without detection to date is not long enough to assume eradication—due
to potential silent transmission, certification of eradication requires at least
3 years without detection of virus.
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Risks associated with OPV2 cessation
 Two main risks are associated with OPV2 cessation
 These risks are mitigated by strengthening routine immunization and
introduction of IPV
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Short-term
risks
• Time-limited risk of cVDPV2
emergence, highest 1-2 years after
OPV2 cessation
Medium &
long term
risks
• Poliovirus re-introduction from a
vaccine manufacturing site, research
facility, immune deficient persons,
diagnostic laboratory, or bioterrorism
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Role of OPV post-eradication
 Maintaining a stockpile of
monovalent OPVs (mOPV1,
mOPV2, mOPV3)
 Using mOPVs to control outbreaks
of cVDPVs or re-introduction from a
manufacturing site, research facility,
or diagnostic laboratory
mOPV1
POLIO
OUTBREAK
posteradication
mOPV2
mOPV3
 Stockpile of mOPVs would allow a
type-specific response for rapid
interruption of outbreak
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Technical Rationale for Introduction for Inactivated Polio Vaccine (IPV)
Key Messages
 Introducing IPV before the tOPV-bOPV switch in 2016 will
ensure that a substantial proportion of the population is
protected against type 2 polio after OPV2 cessation and
mitigate risks associated with OPV2 cessation
 IPV is recommended for routine immunization programmes
& not campaigns
 IPV is given in addition to OPV doses and does not replace
any OPV doses
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Planned use of IPV: SAGE Recommendations
• SAGE recommended that all countries introduce at least 1 dose of IPV in
their routine immunization programmes to mitigate the risks associated with the
withdrawal of type 2 component of OPV
• Single dose of IPV at 14 weeks of age with DTP3, in
addition to OPV3 or OPV4.
• Countries have flexibility to consider alternative
schedules
• All endemic and other high risk countries should
develop a plan for IPV introduction by mid-2014 and all
OPV-only using countries by end-2014
WER, 3 Jan 2014, vol. 89, 1 (pp 1-20): at http://www.who.int/wer/2014/wer8901/en/index.html
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Features of Inactivated Polio Vaccine (IPV)
 Not a live vaccine – no risk of VAPP or VDPVs
 Must be administered by intramuscular or subcutaneous injection
 Trivalent – produces antibodies to types 1, 2 and 3 poliovirus
 A high proportion of vaccinees, generally > 95% of children, have serum
neutralizing antibodies after 3 doses to all three polio serotypes
 Appears equivalent to OPV in inducing pharyngeal immunity
 Inferior to OPV in inducing gut immunity
 More costly to produce than OPV
− Partners are working towards achieving the lowest possible price for GAVI and non-GAVI
countries.
− Collaborations & investigations underway to explore two “low cost” IPV options:
◊ fractional dose intradermal
◊ adjuvanted intramuscular IPV
− GAVI will cover the full cost of purchase for GAVI eligible and graduating countries
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Rationale for introducing at least one dose of IPV prior to the
tOPV-bOPV switch
Introducing IPV before the tOPV-bOPV switch in 2016 will ensure that a
substantial proportion of the population is protected against type 2 polio after
OPV2 cessation. One dose of IPV will:
 Reduce risks associated with
OPV2 cessation
-
Reduce risks
Lower risk of re-emergence of
type 2 polioviruses
 Facilitate interruption of
transmission with the use of
monovalent OPV2 if type 2
outbreaks occur
 Boost immunity against types 1
& 3 thus hastening polio
eradication
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IPV
Interrupt
transmission if
outbreaks occur
Hasten
eradication
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Individual protection against
paralytic disease induced by
IPV – REDUCE RISKS
Reduce risks
IPV
Interrupt
transmission if
outbreaks occur
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Hasten
eradication
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Impact of one dose of IPV*
 Primary role of one dose of IPV is intended to be a RISK MITIGATION
strategy to reduce risk of re-emergence of type 2 polioviruses after OPV2
cessation
 Seroconversion against type 2 after one dose of IPV ranges from 32-63%.
Persons who seroconvert should be protected against paralytic polio
 Seroconversion rates are higher when vaccine is administered later in
infancy presumably because of waning maternal antibody
 Persons who seroconvert should be protected against paralytic polio
Type 2
Author year
Country
Schedule
Seroconversion
Intramuscular administration of 1 dose of IPV
McBean 1988
Simasathien 1994
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US
Thailand
2 mo
2 mo
35%
39%
Resik 2010
Cuba
6 wk
36%
Mohammed 2010
Oman
2 mo
32%
Resik 2013
Cuba
4 mo
63%
* Estı´variz CF et al. Lancet 2012; 12(2):128-35
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Rationale for administering IPV after 14 weeks of age, in the
context of the Endgame Plan
 The immune response to intramuscularly administered IPV varies based on the
number of administered doses (higher with more doses) and the age at
vaccination (higher with delayed immunization).
-
3 doses: ~100% against all 3 serotypes
2 doses: ~90% against all 3 serotypes, when administered >8 weeks of age
1 dose: ~19%-46% against Type 1, 32%-63% against Type 2, and 28%54% against Type 3 poliovirus.
 It is important to note that immune response to one dose of IPV is substantially
higher, particularly against Type 2 poliovirus (63%) when administered at 4
months of age compared to 6 weeks to 2 months of age (32%-39%).
 Thus, SAGE recommends a single dose of IPV at 14 weeks or first contact
afterwards, or with DTP3/OPV3 or for countries administering a birth dose of
OPV, at the time of the OPV4 dose
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Poliovirus type 2 seroconversion & priming
 In a study from Cuba, among those who did not seroconvert after 1 dose of
IPV, 98% had a priming response to a subsequent dose of IPV--that is,
they developed significant antibody responses within 7 days of subsequent
exposure to IPV.
 Persons without priming who are seronegative would not be expected to make
detectable antibody for at least 10-14 days or longer after immunization.
 Persons who are seronegative but primed may also be protected against
paralytic polio although data are conflicting as to whether priming alone is
protective.
IPV administered at 4 months of age
(n=153)
1st dose seroconversion
63%
Priming
98%
1st dose seroconversion & priming
99%
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Sutter RW – Presentation to SAGE IPV Working Group June 2013 based on:
Resik S et al N Engl J Med 2013;368:416-24
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IPV Evidence: One IPV dose prevents VAPP in Hungary.
Implies priming induces clinical protection.
VAPP number of cases
In 1992,
single-dose
IPV at 3 mos of age,
before OPV receipt
In 2006,
IPV-only
schedule
Year
Sutter RW – Presentation to SAGE IPV Working Group In contrast, effectiveness against type 1 in
Senegal was 36% (0%-67%) implying that
June 2013
seroconversion is the predictor of immunity.
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Outbreak control with mOPV2 in a
population which previously
received IPV -- REDUCE RISKS
Reduce risks
IPV
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Interrupt
transmission if
outbreaks occur
Hasten
eradication
31
IPV Evidence: What impact is one dose of IPV in routine immunization
likely to have during SIAs in outbreak situations?
 Impact on seroconversion of IPV followed by OPV
Figure: Giving a single dose of OPV
after a prior dose of IPV gives
comparable immunity** to 2 OPV
doses
is similar to IPV-IPV or OPV-OPV
 Thus, with one dose of IPV a proportion of the
Type 1
population is already immune.
 Use of mOPV in an outbreak control setting in a
population who received a dose of IPV is likely to
lead to higher immunity levels than a single dose of
mOPV in a completely susceptible population
 Thus, population immunity thresholds to terminate
poliovirus transmission are more likely to be
reached after a dose of IPV followed by mOPV
compared to a single dose of mOPV only in
response to an outbreak.
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Type 2
Type 3
100
90
80
70
60
50
40
30
20
10
0
IPV-IPV
OPV-OPV
IPV-OPV
Comparison of 2-dose response, Faden et al, JID, 1990
**These data are based on a US study in Baltimore and Buffalo.
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IPV in reducing transmission of
polioviruses – Interrupt
Transmission
Reduce risks
IPV
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Interrupt
transmission if
outbreaks occur
Hasten
eradication
33
OPV challenge studies: Shedding of poliovirus in IPV versus OPV
vaccinees
 IPV is equivalent to OPV in reducing oral shedding but is inferior to
OPV in reducing intestinal shedding.
 To the degree that polioviruses are transmitted orally, IPV should be
equivalent to OPV.
 To the extent that polioviruses are transmitted via the fecal-oral route, IPV
is likely to be inferior to OPV.
From Vidor E et. al, Poliovirus Vaccine – Inactivated, Vaccines 6th edition, Elsevier, 2013
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Although IPV may not be as effective as OPV in decreasing prevalence of
poliovirus excretion in stool, IPV may still decrease transmission
 IPV does reduce the duration of shedding and the amount of virus shed in the
stool.
 Thus, IPV should decrease the spread of polioviruses if they are introduced,
compared to a fully unvaccinated population.
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From Sutter et al. Poliovirus vaccine-live, Vaccines 6th ed, Elsevier, 2013
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IPV in boosting immunity in
OPV primed individuals –
Hastens Eradication
Reduce risks
IPV
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Interrupt
transmission if
outbreaks occur
Hasten
eradication
36
A single dose of IPV after prior doses of tOPV boosts
immunity to types 1 & 3
•
•
IPV could also play a role in the eradication efforts, in conjunction with bOPV, by
boosting immunity against type 1 and 3 polioviruses in polio endemic countries and
countries where poliovirus circulation has been reestablished.
Immune response to Types 1 & 3 significantly better with IPV at 6 months of age
in children who received three prior doses of tOPV in Ivory Coast but were still
seronegative*
3 tOPV + IPV**
3 tOPV + tOPV**
Type 1 seroconversion
80%
40%
Type 3 seroconversion
76%
22%
** Fourth dose at 6 months
•
•
•
Seroconversion after one dose of IPV in seronegative children with prior OPV
substantially higher than would be expected with one dose of IPV in polio vaccine
naïve children.
Further, IPV in persons with prior OPV induces boosts in mucosal immunity.
Results from a similar study in Moradabad showed 91%-100% seroconversion for
types 3 and 2 respectively among those who received IPV**
*Moriniere BJ et al. Lancet 1993;341:1545-50, ** Estı´variz CF et al. Lancet 2012; 12(2):128-35,
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Schematic description of
technical rationale for use
of at least one dose of IPV
as part of the Endgame
Strategy
tOPV: 3 rings of protection
against types 1, 2, and 3
Type 1
Type 2
Type 3
tOPV-bOPV
switch
bOPV
bOPV
+
IPV
IPV adds protection
against type 2 & boosts
immunity to 1 & 3
(enhancing bOPV
effect)
2 rings of
protection against
types 1 and 3
mOPV2
Potential Type
2 outbreak
requiring
mOPV2
bOPV + IPV
mOPV2
bOPV + mOPV2
Protection against
type 2 provided by
supplementary
use of mOPV2 in
the setting of an
outbreak
bOPV + IPV + mOPV2
bOPV & mOPV2 effect
is enhanced in an IPV
population thus
facilitating outbreak
control
IPV Presentations and Formulations
Stand-alone
IPV
Combination
products
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•
•
•
•
Only WHO prequalified formulation
1-dose and 10-dose available now
5-dose expected in late 2014
Preservative : 2PE does not allow for Multi dose
vial Policy application
•
•
Tetravalent, pentavalent, hexavalent available
Combination with whole-cell pertussis not
currently available
Substantially higher cost than stand-alone IPV
•
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Example 6-10-14 week schedule with IPV
Vaccine
6 weeks
10 weeks
DTP-HepB-Hib
√
√
√
Pneumococcal
√
√
√
Rotavirus*
√
√
√
OPV
√
√
√
BCG
Birth
14 weeks
√
Stand-alone IPV
√
1st contact after 14 weeks
 Single dose of IPV at 14 weeks or first contact afterwards
-
All children who are behind on their schedule should receive one dose of the IPV
at the first immunization contact after 14 weeks
 Countries have flexibility to consider alternative schedules (e.g. earlier IPV
administration based on local conditions)
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* Rotavirus vaccine may be administered in 2 or 3 doses, depending on the country schedule
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Administration of Inactivated Polio Vaccine (IPV)
 IPV is administered by intramuscular injection (IM) or subcutaneously (SQ) in a
dose of 0.5 ml into the outer part of the thigh
 When given at the same visit, IPV and other injectable vaccines should be
given at different injection sites at least 2 cm apart
-
For example, if IPV, Pentavalent vaccine, and Pneumococcal vaccine are to be given
during the same visit, IPV and Pneumococcal should be in one thigh 2 cm apart and
the Pentavalent vaccine (more reactogenic) in the other thigh
 IPV should not be mixed with other vaccines in the same vial or syringe
 IPV can be administered to prematurely born infants and children with
immunodeficiencies (e.g., HIV, congenital or acquired immunodeficiency, sickle
cell disease)
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Multiple Injections: Acceptability and Safety
 Recently, more low and middle income countries have begun using multiple
vaccine injections with the addition of pneumococcal vaccine and IPV
 Substantial evidence has reinforced the well-established record of safety and
acceptance of multiple injections from countries using multiple injections*
- For example, US infants often receive 3 or more injections during each of the primary series
vaccination visits
 Giving a child several vaccinations during the same visit offers three major
advantages:
- Immunizing children as soon as possible provides protection during the vulnerable early months of
their lives.
- Giving several vaccinations at the same time means parents and caregivers do not need to make
as many vaccination visits. 1
- It means that health care providers are able to more efficiently provide and deliver other health
services by reducing the time they need to spend providing vaccinations.
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*http://www.cdc.gov/vaccinesafety/Vaccines/multiplevaccines.html
*http://www.cmaj.ca/content/182/18/E843.full
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Specific notes on the recommended IPV schedule*
 IPV does not replace ANY of the OPV doses – that is, IPV will be
given in addition to OPV and OPV will continue to be used per current
practice for now
 IPV is recommended for routine immunization programmes and
not campaigns because injections are difficult to accommodate in
campaigns against polio
 The higher the IPV coverage the better, but even low coverage will
provide direct benefit to those vaccinated and greatly facilitate
building population immunity in an emergency response
*from 7th Meeting of the SAGE Polio Working Group, October 18-19, 2013
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IPV introduction
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Planned use of IPV: IPV Rationale Summary
 IPV induces immunity in a proportion of children which will protect them against polio
caused by vaccine viruses (VAPP and cVDPVs) and polio caused by wild poliovirus
-
IPV should lower risk of re-emergence of type 2 polioviruses
IPV in conjunction with bOPV will decrease the number of cases of VAPP caused by
types 1 and 3
-
IPV will boost immunity to types 1 and 3 which should hasten eradication of types 1
and 3 wild polioviruses and reduce polio disease caused by types 1 and 3 cVDPVs
-
IPV by inducing immunity to type 2 will facilitate outbreak control with mOPV2
should type 2 viruses be reintroduced
−
A proportion of the population will already be immune resulting in a higher level of immunity after a
dose of mOPV2 in outbreak control than after a dose of mOPV2 to contain an outbreak in a completely
susceptible population
 The higher the IPV coverage the better, but even low coverage will provide direct benefit
to those vaccinated and greatly facilitate building population immunity in an emergency
response
7/24/2016
IPV introduction
44