Assessment of emerging polio risks
cVDPV emergence
Environmental surveillance for poliovirus is
conducted in countries such as
Australia
,
Egypt
,
Haiti
and in Yogjakarta Province,
Indonesia
. This area of work tries to further quantify the risk of cVDPV emergence in
countries or parts of countries that have recently switched from OPV to IPV (Australia
and Yogjakarta Province,
Indonesia). Furthermore, these studies provide more evidence on the usefulness of
environmental surveillance, particularly in
Egypt
and Haiti.
iVDPV prevalence studies
This study series focuses on the rate of
long-term excretion of vaccine-derived poliovirus from immunodeficient
individuals. Country participation in this series of studies is currently
being discussed with approximately ten middle to low-income countries, including
Bangladesh
,
China
and the
Russian Federation
. The purpose of this series of studies is to better define the risk of iVDPV in
middle and low income countries.
Screening
of all Sabin viruses
This
section is in preparation.
return to top
Research to accelerate eradication
Serosurveys
Similar to a seroprevalence
survey conducted in
Egypt, a serosurvey is currently
being conducted in
Moradabad, Uttar Pradesh State,
India
among young infants and children to determine immunity to the three poliovirus
serotypes. The field work has been completed and the results are expected in
early 2008. This survey will help determine the population immunity status in
this area and help the program to determine whether to adjust the schedule of
supplemental immunization activities (SIAs). See selected
publications.
mOPV studies
Following the rapid development and licensure
of monovalent OPV type 1 (mOPV1) and its successful incorporation into
immunization campaigns in numerous countries since 2005, a similar process is
being implemented for monovalent OPV type 3 (mOPV3). Plans are now under way for
the development and licensure of monovalent OPV type 2 (mOPV2).
For the purposes of licensure, as well as WHO pre-qualification, these
vaccines are being studied in a series of comparative evaluations focusing on
the differences in immunogenicity induced between mOPV versus trivalent OPV (tOPV).
These studies are conducted as randomized double-blind trials set in
Egypt, India
, Indonesia
and South Africa.
Bivalent OPV
Building on the successful development, licensure
and use of mOPVs, and given the circulation of only two wild poliovirus
serotypes (types 1 and 3) in the remaining endemic areas, the Global Polio
Eradication Initiative is re-exploring the potential feasibility and role of
bivalent OPV for use in some supplementary immunization activities.
Evaluation
of the role of IPV in India
Assessment of rapid diagnostics
These
sections are in preparation.
return to top
Development of safer IPV production processes and
affordable strategies for use
Sabin-IPV
The major aim of this area of work is to make
IPV "safe for production in developing countries" and potentially
affordable for these settings.
WHO has set up a collaboration between
manufacturers and a national regulatory agency to facilitate the pharmaceutical
development of Sabin-strain-based inactivated polio vaccine (sIPV) to the
proof-of-principle stage, with the ultimate objective of demonstrating the
immunogenicity and reactogenicity of sIPV in an appropriate formulation.
Biological norms and standards for sIPV are being established. Preliminary
results of the pharmaceutical development should be available by mid-2008.
Work on IPV also includes the assessment of
optimal
IPV schedules (in selected publications) and schedule reduction
(in selected publications). In addition, WHO is studying the role of adjuvants in
increasing the immunogenicity of IPV.
return to top
Long-term surveillance and response
Polio antiviral research
Over the past few years, the Global Polio
Eradication Initiative has been considering the potential role of antivirals in
outbreak response and to clear chronic poliovirus infection among
immunodeficient individuals. Ongoing discussions have been taking place on
the feasibility of developing polio antivirals: in November 2005, the National
Academy of Sciences (at the request of CDC and WHO) hosted a workshop on
antiviral compounds. Possible approaches under review include capsid inhibitors,
protease inhibitors, and RNA inhibitors. A final
report (see selected publications) with recommendations on this subject was published in February
2006. Subsequently, limited funding has been identified to conduct further
research on capsid inhibitors. A collaborative effort to develop these compounds
is led by the Taskforce on Child Survival and Development in Atlanta.
Study on use of IPV in outbreak response
If an appropriate
opportunity were to occur, the Global Polio Eradication Initiative would examine
the potential for using IPV in outbreak control. The primary purpose of these
efforts would be to confirm that IPV can interrupt poliovirus transmission in a
developing-country, tropical setting.
return to top
Long-term containment of
polioviruses
Global Action Plan
The WHO Global Action
Plan to minimize poliovirus
facility-associated risks in the post-eradication/post-OPV era (GAP III, see selected
publications) was
drafted in 2007. GAP III provides a long-term vision and rational plan to ensure
that polioviruses are not reintroduced to human populations once transmission
has been interrupted. GAP III is currently being revised based on comments from
the public health community.
return to top
Options for safely stopping OPV use
Development of strategy options for OPV cessation
Guidelines for OPV withdrawal and destruction
These sections are in preparation.
IPV demonstration project
The Global Polio Eradication Initiative
launched in 2004 demonstration project in the province of Yogyakarta, Indonesia
on the use of IPV in a developing tropical country in order to: 1) determine the
operational feasibility of IPV introduction; and 2) to answer key scientific
questions that could influence a possible future recommendation for an IPV-only
schedule for developing tropical countries.
Yogyakarta
province was selected because it presented an
optimal setting for such a policy switch, including high routine immunization
coverage (<95%) and the opportunity to conduct environmental surveillance.
After extensive planning and preparation, as well as delays due to a 2005 wild
poliovirus outbreak in Indonesia, the policy switch from OPV to IPV took place on 3 September 2007. The
objectives of the IPV project are to evaluate the operational and programmatic
issues surrounding the change to IPV and evaluate through environmental
surveillance whether IPV-induced immunity precludes the emergence of VDPVs in
this tropical setting. To date, the adoption of IPV in Yogyakarta
province has proven to be successful and feedback remains positive.
Selected publications
Survey of poliovirus antibodies during
the final stage of polio eradication in Egypt.
PDF from Vaccine,
Volume 25, Issue 27, 28 June 2007, pp 5062-5070.
Serologic Response to Inactivated
Poliovirus Vaccine: A Randomized Clinical Trial Comparing 2 Vaccination
Schedules in
Puerto Rico, abstract available at Journal
of Infectious Disease, Issue 2007;195:12-20.
Randomized,
Placebo-Controlled Trial of Inactivated Poliovirus Vaccine in
Cuba, New England
Journal of Medicine, Volume 356:1536-1544.
Exploring the role of antiviral drugs in
the eradication of polio, Workshop
Report, National Academy of Sciences, 2006.
WHO
Global Action Plan
(pdf) to
minimize poliovirus facility-associated risks in the post-eradication/post-OPV
era.
return to top
|
