Saturday, September 1, 2018

PRO/EDR> Poliomyelitis update (39): Global, WPV & cVDPVs, cVDPV post OPV2 cessation

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In this update:
[1] Global (Afghanistan, DR Congo, Nigeria, Papua New Guinea) - GPEI
[2] VDPV2 post "cessation" of OPV2 - NEJM

[1] Global (Afghanistan, DR Congo, Nigeria, Papua New Guinea) - GPEI
Date: Fri 31 Aug 2018
Source: Global Polio Eradication Initiative / WHO [edited]

Poliovirus weekly update as of 28 Aug 2018 World Health Organization
New wild poliovirus cases reported this week: 1
Total number of wild poliovirus cases in 2018: 15
Total number of wild poliovirus cases in 2017: 22

New cVDPV cases reported this week: 7
Total number of cVDPV cases (all types) in 2018: 32
Total number of cVDPV cases (all types) in 2017: 96

Summary of new viruses this week:
- Afghanistan - 1 new wild poliovirus type 1 (WPV1) case
- Democratic Republic of the Congo (DRC) - based on positive contacts,
2 negative acute flaccid paralysis (AFP) index cases classified as
circulating vaccine-derived poliovirus type 2 (cVDPV2)
- Nigeria - 3 new cases of cVDPV2
- Papua New Guinea - 2 new cases of cVDPV1
- To assess if the 2016 trivalent-bivalent oral polio vaccine "switch"
was successful, a group of researchers from Imperial College London,
WHO, and the Bill & Melinda Gates Foundation analysed stool and sewage
samples from 112 countries collected in the 1st 15 months after the
switch. Study results were published this week in The New England
Journal of Medicine (see section [2]).

Weekly country updates as of 28 August 2018
- 1 new case of WPV1 was reported this week from Agam district,
Nangahar province, with onset of paralysis on [17 Jul 2018].
- The total number of cases reported in Afghanistan in 2018 is 12.
- During the August [2018] immunization campaign, almost 10 million
children were visited by vaccination teams to protect them from the

- No new cases of WPV1 were reported this week.
- The total number of WPV1 cases reported in Pakistan in 2018 is 3.
- The latest case, from Dukki district, Balochistan province, had
onset of paralysis on [18 May 2018].

- 3 new cVDPV2 cases were reported this week: 1 each from Miga local
government area (LGA), Jigawa state (date of onset [27 Jun 2018]);
Babura LGA, Jigawa state (date of onset [24 Jul 2018]); and Baure LGA,
Katsina state (date of onset [27 Jul 2018]).
- No new cases of WPV1 were reported in the past week. The most
recently detected WPV1 case, from Borno state, had onset of paralysis
on [21 Aug 2016].
- The country continues to be affected by 2 separate cVDPV2 outbreaks,
the 1st centered in Jigawa state, and the 2nd in Sokoto state.
- In response to cVDPV2 detection, the country continues to conduct
AFP surveillance-strengthening activities, including enhanced active
surveillance visits and community sampling. The programme has also
carried out an extensive search for type 2-containing vaccines
(tOPV/mOPV2) in the areas surrounding where the virus is detected.
- The GPEI is working with regional and country counterparts and
partners to support an outbreak response and plan the October [2018]
sub-national immunization activity.
- At the same time, outbreak response to WPV1 continues, including
efforts to address surveillance and immunity gaps in parts of Borno

Lake Chad Basin
- The detection of WPV1 and cVDPV2 in Nigeria continue to pose a risk
to the neighbouring countries of the Lake Chad basin.
- Emergency outbreak response efforts continue across the Lake Chad
basin, together with activities to fill subnational surveillance gaps
in the region.
- These include efforts to vaccinate children at markets, in
internally displaced persons and refugee camps, and at international
- Preparations continue for a cross-border synchronized immunization
activity in October [2018].

Central Africa
- In DRC, based on [12 and 22 Jul 2018], respectively). The total
number of cases detected in the country in 2018 is now 13.
- The country is affected by 3 separate strains of cVDPV2, in the
provinces of Mongola, Maniema and Haut Lomami/Tanganika/Haut
- In response to recent geographic spread of one of the strains,
including to Ituri province close to the border with Uganda,
provincial governors on [26 Jul 2018] convened an urgent meeting and
signed the "Kinshasa Declaration for Polio Eradication."
- The high-level meeting was convened by HE the minister of health, as
well as the WHO director-general and the regional director for Africa.
Provincial governors committed to providing the necessary oversight,
accountability, and resources needed to urgently improve the quality
of the outbreak response being implemented across the country.
Outbreak response since cVDPV was 1st confirmed in 2017 has been
marred by operational challenges, as too many children continue to
remain un- or under-vaccinated. This level of oversight can help
ensure that operational deficits are rapidly identified and
- The polio outbreak response is being conducted simultaneously to an
ongoing Ebola outbreak affecting North Kivu province, in the east of
the country (close to provinces affected by cVDPV2). As in the past,
the polio teams are coordinating closely with the broader humanitarian
emergency network, to ensure both outbreaks are addressed in a
coordinated manner (as was the case during the recent Ebola outbreak
in Equateur province, which was successfully stopped).
- Partners of the Global Polio Eradication Initiative will continue to
support authorities across the country to ensure that this new level
of commitment rapidly translates into operational improvements on the

Horn of Africa
- The Horn of Africa is currently affected by separate outbreaks of
cVDPV2 and cVDPV3, reporting both cases and environmental positives.
- No new cases were reported this week. The last case of cVDPV2, from
Daynile district, Banadir province, Somalia, had onset of paralysis on
[10 Jul 2018].
- Somalia has reported a total of 5 cases in 2018: 2 cVDPV2, 2 cVDPV3,
and 1 cVDPV2&3.
- cVDPV2 has also been detected during 2018 in 1 environmental sample
in Kenya.
- Outbreak response to both virus types is currently being implemented
in line with internationally-agreed guidelines. Large-scale
supplementary immunization activities (SIAs) have been implemented in
Banadir, Lower Shabelle, and Middle Shabelle regions, Somalia, with
additional SIAs planned or carried out in the affected zones of the
Horn of Africa. Special surveillance activities are being undertaken
to determine the origin of the viral circulation.
- WHO and partners continue to support local public health authorities
across the Horn of Africa in conducting field investigations and risk

Papua New Guinea
- 2 new cases of cVDPV1 were reported this week, from Madang (date of
onset [11 Jul 2018]) and Eastern Highland (date of onset [26 Jul
2018]) provinces.
- The total number of cases in the country in 2018 is now 6 (2 from
Eastern Highland, 1 from Enga, 1 from Madang, and 2 from Morobe
- Papua New Guinea officially launched the outbreak response campaign
on [16 Jul 2018] in Morobe, Madang, and Eastern Highlands provinces.
Three more campaigns are planned for late August, September, and
October [2018].
- With confirmation of recent cases in Eastern Highland and Enga
province, the geographic extent of the outbreak response is currently
being reviewed and will be expanded as necessary.
- Intensified surveillance measures to improve detection of AFP and
poliovirus are being implemented across the country, with
on-the-ground training for provincial and district staff being
provided by NDOH and WHO.

The Middle East
- No new cases of cVDPV2 were reported in the past week in Syria. The
total number of officially reported cVDPV2 cases in Syria in 2017
remains 74. There are no cases reported in 2018. The most recent case
(by date of onset) was reported in Boukamal district, with onset on
[21 Sep 2017].

Officially reported wild poliovirus cases as of 28 Aug 2018
Total global cases in 2018: 15 (compared with 9 for the same period in
Total in endemic countries in 2018: 15 (compared with 9 for the same
period in 2017)
Total in nonendemic countries in 2018: 0 (compared with 0 for the same
period in 2017)

- Afghanistan: 12 cases in 2018 (compared with 6 for the same period
in 2017); onset of paralysis of most recent case 17 Jul 2018
- Pakistan: 3 cases in 2018 (compared with 3 for the same period in
2017); onset of paralysis of most recent case 18 May 2018
- Nigeria: 0 cases in 2018 (compared with 0 for the same period in
2017); onset of paralysis of most recent case 21 Aug 2016

Total global cases in 2017: 22
Total in endemic countries: 22
Total in nonendemic countries: 0

Officially reported cVDPV cases as of 28 Aug 2018
Total global cases in 2018: 32 (compared with 47 for the same period
in 2017)
- Syrian Arab Republic: 0 cases in 2018 (compared with 39 for the same
period in 2017); onset of paralysis of most recent case 21 Sep 2017
- DRC: 13 cases in 2018 (compared with 8 for the same period in 2017);
onset of paralysis of most recent case 22 Jul 2018
- Nigeria: 8 cases in 2018 (compared with 0 for the same period in
2017); onset of paralysis of most recent case 27 Jul 2018
- Somalia (type 2 and type 3): [5] cases (one cVDPV2 and one cVDPV3
isolated from the same child) in 2018 (compared with 0 for the same
period in 2017); onset of paralysis of most recent case 10 Jul 2018
- Papua New Guinea (type 1): 6 cases in 2018 (compared with 0 for the
same period in 2017); onset of paralysis of most recent case [26 Jul

Total global cases in 2017: 96
Total in endemic countries: 0
Total in nonendemic countries: 96

Communicated by:

[The good news this week is that there were no new WPV1 cases reported
from Pakistan and Nigeria, making it 3.5 months since the last case
was reported in Pakistan, and just over 2 years since the last case
was reported in Nigeria. There were no reports of positive
environmental sampling in any country.

The not-so-good news is that the number of cVDPV cases continues to
increase, with new cases reported from Nigeria, the DRC, and Papua New

As mentioned in previous posts, as the wild poliovirus is decreasing
in prominence, and has disappeared from all but the 3 endemic
countries, the vaccine virus has increased its presence as a major
challenge in countries that have interrupted the WPV transmission
through major campaign activities but have not been able to keep up
the high levels of vaccination coverage following declaration of
polio-free status in the country.

The global map of WPV and cVDPV cases can be found at:
<> (I recommend
using Internet Explorer to see the map clearly).

HealthMap/ProMED-mail maps:
Pakistan: <>
Afghanistan: <>
Nigeria: <>
Congo DR: <>
Somalia: <>
Papua New Guinea: <> - Mod.MPP]

[2] VDPV2 post "cessation" of OPV2 - NEJM
Date: Wed 29 Aug 2018
Source: Global Polio Eradication Initiative [edited]

In April 2016, the polio programme embarked on a massive, coordinated
effort to withdraw Sabin type-2 from routine use, through a
synchronized switch from the trivalent formulation of the oral
poliovirus vaccine (tOPV) to the bivalent form (bOPV). Over a 2-week
period, 155 countries and territories successfully made this change,
marking the largest and fastest vaccine rollout in history.

Referred to as simply "the switch," this global undertaking was a
major programmatic achievement, but it was also a necessary step on
the road to eradication. That's because, in rare cases, the live,
weakened virus contained in OPV can mutate and spread, resulting in
cases of cVDPVs. The vast majority of these cases are caused by just
one of the 3 components contained in tOPV (Sabin type-2 virus), so
switching to a bivalent form that doesn't contain this component was
an attempt to significantly minimize the risk of further cVDPV2 cases,
a decision that was endorsed by the global health community. Further,
with Sabin type-2 responsible for 40 percemt of vaccine-associated
paralytic polio (VAPP) occurrences -- a much rarer phenomenon at 2-4
cases per 1 million -- there was even stronger justification for the

To assess whether the switch was successful, a group of researchers
from Imperial College London, the World Health Organization, and the
Bill & Melinda Gates Foundation analysed stool and sewage samples from
112 countries collected in the 1st 15 months after the switch. The
results, published in The New England Journal of Medicine, show that
VDPVs and Sabin type-2 excreted into the environment after vaccination
disappeared rapidly after the switch, shrinking to a much smaller
geographic area.

These findings validate the GPEI decision to withdraw tOPV and
demonstrate that the switch achieved its desired goal of reducing
VDPVs and VAPP. This research also provides important evidence that
the complete withdrawal of OPV after eradication of all wild
polioviruses will eventually eliminate the risk of VDPVs, provided
high immunity and effective surveillance are maintained. Eradication
is simply not compatible with continued use of OPV.

However, the study also showed that, while some outbreaks of VDPV were
expected post-switch, the number and magnitude of some of these
outbreaks in different geographies has proven more difficult to
control than expected. Type-2 VDPV outbreaks outside of Africa have
been responded to with monovalent type-2 OPV (mOPV2) and controlled.
However, outbreaks in the Horn of Africa, DRC, and Nigeria have been
very difficult to bring to a rapid close.

VDPV outbreaks emerge in areas with very low population immunity, due
to low immunization coverage. Factors which enable them -- insecurity
and resulting inaccessibility, weak health systems, and poor campaign
performance -- are the same that need to be addressed to stop their
transmission. While the programme is aware of these risk factors and
has proven experience and strategies to respond to them, the longer
outbreaks persist, the harder they can be to stop.

The key to stopping these outbreaks will be to increase the focus on
improving the quality of vaccination campaigns in accessible areas. In
inaccessible areas, we need to use all available means to negotiate
access and implement vaccination campaigns. Achieving high-quality
campaign activities will give us the best chance to stop all types of
poliovirus for good and prevent any child from being paralysed by the
virus ever again.

[Byline: Roland Sutter]

Communicated by:

[The study referred to in the GPEI discussion above:
Blake IM, Pons-Salort M, Molodecky NA., Diop OM., Chenoweth P,
Bandyopadhyay AS, Zaffran M, Sutter RW, Grassly NC. Type 2 Poliovirus
Detection after Global Withdrawal of Trivalent Oral Vaccine. N Engl J
Med. 2018; 30 Aug 2018. 379:834-845. doi: 10.1056/NEJMoa1716677


"Mass campaigns with oral poliovirus vaccine (OPV) have brought the
world close to the eradication of wild poliovirus. However, to
complete eradication, OPV must itself be withdrawn to prevent
outbreaks of vaccine-derived poliovirus (VDPV). Synchronized global
withdrawal of OPV began with serotype 2 OPV (OPV2) in April 2016,
which presented the 1st test of the feasibility of eradicating all

"We analyzed global surveillance data on the detection of serotype 2
Sabin vaccine (Sabin-2) poliovirus and serotype 2 vaccine-derived
poliovirus (VDPV2, defined as vaccine strains that are at least
0.6percent divergent from Sabin-2 poliovirus in the viral protein 1
genomic region) in stool samples from 495 035 children with AFP in 118
countries and in 8528 sewage samples from 4 countries at high risk for
transmission; the samples were collected from [1 Jan 2013] through [11
Jul 2018]. We used Bayesian spatiotemporal smoothing and logistic
regression to identify and map risk factors for persistent detection
of Sabin-2 poliovirus and VDPV2.

"The prevalence of Sabin-2 poliovirus in stool samples declined from
3.9 percent (95 percent confidence interval [CI], 3.5 to 4.3) at the
time of OPV2 withdrawal to 0.2 percent (95 percent CI, 0.1 to 2.7) at
2 months after withdrawal, and the detection rate in sewage samples
declined from 71.0 percent (95 percent CI, 61.0 to 80.0) to 13.0
percent (95 percent CI, 8.0 to 20.0) during the same period. However,
12 months after OPV2 withdrawal, Sabin-2 poliovirus continued to be
detected in stool samples (less than 0.1 percent; 95 percent CI, less
than0.1 to 0.1) and sewage samples (8.0 percent; 95 percent CI, 5.0 to
13.0) because of the use of OPV2 in response to VDPV2 outbreaks. Nine
outbreaks were reported after OPV2 withdrawal and were associated with
low coverage of routine immunization (odds ratio, 1.64 [95 percent CI,
1.14 to 2.54] per 10 percent absolute decrease) and low levels of
population immunity (odds ratio, 2.60 [95 percent CI, 1.35 to 5.59]
per 10 percent absolute decrease) within affected countries.

"High population immunity has facilitated the decline in the
prevalence of Sabin-2 poliovirus after OPV2 withdrawal and restricted
the circulation of VDPV2 to areas known to be at high risk for
transmission. The prevention of VDPV2 outbreaks in these known areas
before the accumulation of substantial cohorts of children susceptible
to type 2 poliovirus remains a high priority. (Funded by the Bill and
Melinda Gates Foundation and the World Health Organization.)"

The summation paragraph at the end of the conclusions section of this
paper is critical: "...The withdrawal of OPV2 is a test of the Global
Polio Eradication Initiative strategy to eradicate all polioviruses,
including the live vaccine-derived virus. Our findings provide
evidence that supports the planned withdrawal of bivalent OPV after
eradication of wild polioviruses is confirmed, provided that a high
level of immunity and effective surveillance is maintained in
high-risk areas. Nonetheless, in 2017, the number of poliomyelitis
cases associated with cVDPV2 (96 cases) exceeded those caused by wild
poliovirus (22 cases) for the 1st time, and outbreak-response
campaigns with monovalent OPV2 are continuing in several countries.
Timely control of these outbreaks in the context of a growing cohort
of children who do not have immunity to type 2 poliovirus is critical
to the success of polio eradication."

As I've pointed out in prior commentaries, in essence, the very
vaccine that has facilitated the elimination of wild poliovirus
circulation in all but 3 endemic countries, the oral poliovirus
vaccine (OPV), seems to be coming back to bite us now in the form of
challenges associated with cVDPVs, with reversion in neurovirulence of
the attenuated vaccine viruses. And remembering the situation in the
USA in the 1970s: the USA had virtually eliminated transmission of the
WPV except for an isolated outbreak in a non-vaccinated religious
group, related to an outbreak in the Netherlands and Canada, of a
virus apparently genetically related to a virus identified as
circulating in Turkey. With the picture of limited importations of
WPVs among inadequately vaccinated returning travellers, the majority
of cases of acute paralytic poliomyelitis were associated with the OPV
and OPV-related viruses (we did not have the capacity for molecular
diagnostics of isolates in those days, but all vaccine associated
cases were classified then as either in recipients or in contacts of
vaccine recipients). In other words, we began recognizing that our
main challenge was the vaccine we were using.

In the perspectives article accompanying Blake et al's paper,
(Pallansch MA. Ending Use of Oral Poliovirus Vaccine: A Difficult Move
in the Polio Endgame. N Engl J Med 2018; 30 Aug 2018. 379:801-803.
doi: 10.1056/NEJMp1808903,
<>), Pallansch
raises an important caution in interpreting and extrapolating the data
from Blake's paper: "The analysis by Blake et al. covers the 1st 2
years after the switch, when it was too early to detect any clear
trends as a function of time after the last OPV2 use. Since, as the
authors note, universal introduction of a single dose of IPV has not
resulted in high coverage as originally planned, in part because of a
global supply shortage, several countries have seen dramatic decreases
in population immunity to type 2 poliovirus among children born after
the switch. How this heterogeneity among countries in decreasing
immunity will affect the likelihood and severity of future outbreaks,
the choices made regarding outbreak responses, the risk of new cVDPV
emergence, and the ultimate disappearance of type 2 poliovirus is not
clear from this analysis. Answers to these questions not only are
important for the completion of the OPV2 switch but also could
significantly affect planning for the ultimate cessation of all OPV

I'd add my own caution here: beware of Mother Nature. She has been,
and continues to be, full of surprises, and we need to ensure that
active surveillance will continue for years following the apparent
interruption of circulation of WPV1 and the cVDPVs (remember the
reappearance of WPV1 in Borno, Nigeria, with a virus that had last
been identified in Borno 5 years earlier). - Mod.MPP]

[See Also:
Poliomyelitis update (38): global (Congo DR, Nigeria, Somalia)
Poliomyelitis update (37): global (Afghanistan, Nigeria, Papua New
Poliomyelitis update (36): Papua New Guinea (EH)
Poliomyelitis update (35): (Papua New Guinea, Nigeria, El Salvador)
Poliomyelitis update (34): Nigeria, cVDPV, WHO
Poliomyelitis update (33): Papua New Guinea (EG)
Poliomyelitis update (32): global (DR Congo, Nigeria, Papua New
Guinea), cVDPV
Poliomyelitis update (31): global, Afghanistan, Nigeria
Poliomyelitis update (30): global, WPV, cVDPV, vaccine reaction,
Poliomyelitis update (20): (Pakistan) WPV1 conf.
Poliomyelitis update (10): Congo DR, cVDPV
Poliomyelitis update (01): global (Afghanistan)
Poliomyelitis update (47): Pakistan, global (Congo DR)
Poliomyelitis (01): Pakistan (GB), global, RFI
Poliomyelitis update (21): IPV shortage, global
Poliomyelitis update (01): India, VDPV, wild type-free]
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