COMMENTARY

Niger J Paed 2013; 40 (1):15 –23

Tagbo BN

Achieving polio eradication in

Nigeria: prospects and challenges

DOI:http://dx.doi.org/10.4314/njp.v40i1,3

Accepted: 24th July 2012

Abstract The Global polio eradica-

tion initiative was launched in 1988

by the international community.

Since then, tremendous progress has

been made (99%). However, the last

that has never interrupted the trans-

mission of the poliovirus compared

to more than 125 countries in 1988.

What are the prospects and chal-

lenges to polio eradication in Nige-

ria? This paper discusses these and

other relevant issues regarding po-

lio eradication in Nigeria.

(

)

Tagbo B

Institute of Child Health,

University of Nigeria Teaching

Hospital Ituku-Ozalla Enugu,

Enugu State Nigeria.

1

% of the journey has experienced

several setbacks and rate of progress

has slowed down in the last few

years. Nigeria is one of the remain-

ing 3 endemic countries in the world

Email: tagbobeckie@yahoo.com

Introduction

Trends

Polio virus

2

Polio cases drastically reduced by more than 99% from

an estimated 350,000 in 1988 to 1,352 reported cases in

Polio or poliomyelitis is an acute viral disease character-

ized by inflammation of the nerve cells of the brain stem

and the spinal cord. The disease is caused by a virus

called Poliovirus. It belongs to the genus, Enterovirus

and the family, Picornaviridae. Viruses in this family are

small in size with single stranded RNA. There are 3 se-

rotypes: types 1, 2 and 3. Type 1 is the commonest and

most virulent. Type 2 has not been detected globally

1

2010 . The number of endemic countries has reduced

from 125 in 1988 to 3 in 2012. However, in 2009-2010,

23 previously polio-free countries were re-infected from

3

importations . Tables 1a and 1b show the trend of re-

ported wild poliovirus cases from 2010 to 2012.

1

since 1999 .

Table 1a: Reported wild poliovirus (WPV)₃c_,₄ases,* by type (WPV1 or WPV3) and category of polio-affected country — world-

wide, January–March 2010, 2011 and 2012 .

January-March 2010

January–March 2011

January–March 2012

Category/Country†

WPV1 WPV3

All WPV

WPV1 WPV3

All WPV WPV1 WPV3

All WPV

Polio-endemic countries

Afghanistan

7

1

33

6

40

7

35

1

2

—

37

1

40

6

9

—

49

6

India

3

16

2

19

2

1

—

2

1

—

21

13

—

7

—

28

15

Nigeria

---

3

6

8

Pakistan

9

12

27

—

27

2§

Countries with reestab-

lished transmission

Angola

1

7

---

8

1

77

2

3

—

80

2

3

—

0

—

3

—

Chad

---

7

33

3

36

3

—

3

Democratic Republic of

the Congo

---

16

---

80

---

96

42

—

10

42

—

86

—

16

—

Total**

224

234

104

*

Case data reported to the World Health Organization as of May 15, 2012, by date of onset.

†

§

*

Country category based on Global Polio Eradication Initiative 2010–2012 Strategic Plan

Includes one mixed WPV1/WPV3.

*Countries affected by outbreaks are excluded in this table

1

6

Table 1b: Reported wild polioviru₃s_,₄(WPV) cases,* by type (WPV1 or WPV3) and category of polio-affected

country — worldwide, 2010–2011

Total 2010

WPV1

Total 2011

WPV1

Category/Country†

Polio-endemic countries

Afghanistan

India

WPV3

69

All WPV

232

25

WPV3

17

All WPV

163

17

18

8

324

80

1

341

80

1

8

—

24

42

—

Nigeria

13

21

47

196

15

62

198

Pakistan

120

24

144

2

Countries with reestablished trans-

mission

144

33

15

---

15

159

33

227

5

3

230

5

Angola

Chad

—

3

11

26

129

132

Democratic Republic of the

Congo

100

614

---

100

782

93

—

40

93

Total**

168

1102

1142

**Countries affected by outbreaks are excluded in this table

5

Table 2 shows the trend of vaccine derived polioviruses worldwide from July 2009 to March 2011 .

Table 2: Vaccine-derived polioviruses (VDPVs) detected --- worldwide, July 2009--March 2011

No. of isolates§ July 2009--March

011

Routine

Current status

2

VP1 diver- coverage Estimated

duration of⁽

date of last out-

gence

break case, last

from Sabin doses of VDPV

patient isolate, or

last environmental

sample)

Year(s) Source (total

de- cases or

tected* specimens)†

with 3

Category Country

Serotype

Non-AFP

source

OPV strain polio

%) vaccine

%)¶

replica-

tion**

Cases

Contacts

(

cVDPV†† Afghanistan₂²₀₁₁

010--

Outbreak (6

cases)§§

Importation

2

6

---

1.0--2.7

5.3

83¶¶

36

2.5 yrs

---

January 20, 2011

November 10,

2010

Chad

2010

1

(1 case)***

2

008-- ^O^u^t^b^r^e^a^k⁽³⁷ 2

010 cases)

009-- Outbreak (7

010

009-- ^O^u^t^b^r^e^a^k⁽¹⁶ 2

010 cases)

DRC†††

Ethiopia

India

17

7

0.7--3.5

1.3--3.1

1.0--1.6

2.5

68

3.2 yrs

2.8 yrs

1.5 yrs

---

October 26, 2010

November 4, 2010

January 31, 2010

June 1, 2010

3

60

cases)

16

1

50§§§

71

2

006-- ^I^m^p^o^r^t^a^tⁱ^oⁿ^s 2

Niger

010 (5 cases)***

Outbreak

(355 cases)

2

005--

011

Nigeria¶¶¶

Somalia

2

48

5

---

6

---

0.7--6.2

0.7--2.8

61

26

6 yrs

March 7, 2011

March 22, 2011

****

2

008-- ^O^u^t^b^r^e^a^k⁽¹³ 2

2.6 yrs

011 cases)

Abbreviations: cVDPV = circulating VDPV; DRC = Democratic Republic of Congo; iVDPV = immunodeficiency-associated VDPV; aVDPV =

ambiguous VDPV; OPV = oral poliovirus vaccine; IPV = inactivated poliovirus vaccine; AFP = acute flaccid paralysis.

*

†

§

¶

Total years detected and cumulative totals for previously reported cVDPV outbreaks (DRC, Ethiopia, and Nigeria).

Outbreaks list total cVDPV cases. Some VDPV case isolates from outbreak periods might be listed as aVDPVs.

Total cases for VDPV-positive specimens from AFP cases and total VDPV-positive samples for environmental (sewage) samples.

Based on 2009 data from the World Health Organization (WHO) Vaccine Preventable Diseases Monitoring System (2010 global summary) and

WHO-UNICEF coverage estimates, available at http://www.who.int/immunization_monitoring/en/globalsummary/countryprofileselect.cfm

National data might not reflect weaknesses at subnational levels.

.

** Duration of cVDPV circulation was estimated from extent of VP1 nucleotide divergence from the corresponding Sabin OPV strain; duration of

iVDPV replication was estimated from clinical record by assuming that exposure was from initial receipt of OPV; duration of aVDPV replication

was estimated from sequence data.

†

§

† Most cVDPV isolates from Afghanistan, Chad, DRC, Ethiopia, Niger, Nigeria, and Somalia were vaccine/nonvaccine recombinants.

§ Three cases from 2009 are not included in the count because they had <10 nucleotide substitutions in VP1 and the new definition was not yet

implemented.

¶ Routine trivalent OPV coverage was 14% among case-patients.

¶

*** Importations from Nigerian cVDPV outbreak. One imported VDPV from Niger had been previously incorrectly assigned to be from Guinea.

††† Previously reported outbreak. Additional information available at http://www.cdc.gov/mmwr/preview/mmwrhtml/mm5836a3.htm.

§§§ cVDPVs clustered in Uttar Pradesh and Bihar, where routine coverage with trivalent OPV was ~50%.

¶¶¶ Previously reported outbreak. Additional information available at http://www.cdc.gov/mmwr/preview/mmwrhtml/mm5836a3.htm.

**** Count does not include 29 cases with <10 nucleotide substitutions in VP1 detected before 2010.

1

7

The global estimation of routine trivalent OPV (tOPV)

vaccination coverage (3 doses of tOPV by 12 months)

by the end of 2010 was 86%. The WHO Regional cover-

ages were 79%, 93%, 96% and 77% for African, the

Americas, European and West Pacific, and South-East

Asian Regions respectively . Some indicators of success

6

of the global polio eradication efforts are shown in

1

table 3 .

Table 3: Selected indicators of the success of the Global Polio Eradication Initiative

Parameter

1988

2000

2006

2009

No. of new cases per year

No. of endemic countries

No. of endemic WHO Regions

No. of circulating wild WPV serotypes

No. of remaining WPV genotypes#

300 000

>125

719

1997

1606

20

4

6

3

2

WPV1: 20

WPV2: 5

WPV3: 17

WPV1: 9

WPV2: 0

WPV3: 7

WPV1: 2

WPV2: 0

WPV3:2

WPV1: 2

WPV2: 0

WPV3: 2

WPV, Wild-type poliovirus.

#

sequence >15%) that are considered to have epidemiological linkage with each other .

A genotype is a group of genetically closely related poliovirus strains (difference in capsid protein VP1 coding

1

Transmission

Vaccination

Polioviruses are mainly transmitted through the faeco-

oral route (via stool contaminated food and water) and

also by person to person contact. They are acid resistant

and therefore able to travel safely through the stomach

to settle in the gut where they replicate. Therefore trans-

mission occurs most in areas with poor personal and

environmental hygiene. Polioviruses can survive for

weeks in water and sewage. Poliomyelitis is highly in-

fectious and transmission is expected to occur in almost

Polio has no cure: clinical cases can only be managed

with supportive care. Therefore, prevention is the main-

stay of management of polio. Apart from improvement

in hygiene and sanitation standards, vaccination is the

primary mode of prevention. Primary and booster doses

of polio vaccine protects most vaccinees for life.

Two vaccines are currently available namely the live

attenuated Oral Polio Vaccine (OPV), developed by

Albert Sabin; and the Inactivated (killed) Polio Vaccine

(IPV) developed by Jonas Salk. Both vaccines are triva-

lent, though recently, bivalent (bOPV) and monovalent

(mOPV) vaccines have been produced for data-driven

supplementary immunization activities (SIAs) in some

endemic countries.

1

00% of susceptible children and more than 90% of

susceptible adult household contacts. In general, trans-

mission is higher in developing countries. Additionally,

other factors that determine the ease and spee₇d of spread

include population density and rate of contact .

From the gut the viruses reach the central nervous sys-

tem through the blood stream to cause disease. The incu-

bation period is 7-14 days (4-35 days). Polio can be

symptomatic (4-8%) or asymptomatic (~95%); paralytic

Although OPV is safe, rare adverse event could occure

and Vaccine associated paralytic polio (VAPP) is one of

the most important of these rare adverse events. While

OPV virus has the potential to revert to a live virus that

is capable of causing paralysis, IPV cannot cause polio.

The vaccine associated paralysis is caused by mutation

or reversion of the Sabin virus to neurovirulence. Such

circulating vaccine derived polio viruses (cVDPVs)

therefore can result in polio cases and paralysis similar

to that caused by wild polio viruses (WPVs). Vaccine

associated paralytic polio occurs in both vaccinees and

1

or non-paralytic (99%) . On the average, only 1 in 200

infections will result in acute flaccid paralysis (AFP).

8

Paralytic polio could be spinal, bulbar or bulbo spinal .

Clinical features

The symptoms include fever, headache, vomiting, fa-

tigue, neck and back stiffness and muscle pains. Other

clinical features are paralysis of the limbs and respira-

tory muscles, respiratory failure, swallowing difficulty,

urinary retention, constipation, diarrhoea and abnormal

sensations (but not loss of sensation). Severity increases

with increasing age of infection. Only about 0.1-2% of

infected people have paralytic polio out of which 5-10%

die of respiratory failure. Recovery from an infection

7

their unimmunized contacts . Although wild_,₂t_,y₇pe 2 polio

1

virus has been eliminated since 1999 , type 2

cVDPVs are still being reported in some endemic coun-

tries.

In a few individuals with primary B-cell immunodefi-

ciency, there is chronic shedding of the Sabin virus with

increased neurovirulence. Such viruses are called immu-

nodeficiency-associated vaccine derived polioviruses

8

confers serospecific immunity .

(

iVDPV). These are not known to occur in HIV infec-

1

8

Definitions

individuals thereby conferring immunity on them.

This is the direct effect of the vaccine (herd immunity)

1

2

. These herd effects result in a population immunity

The following definitions were given by the Dahlem

Workshop on Disease Eradication in 1997 and published

by the C₉enters for disease control and prevention (CDC)

in 1999 :

that is higher than the sum of the individual immunity of

the vaccinated individuals in the community.

•

Control: The reduction of disease incidence, preva-

lence, morbidity or mortality to a locally acceptable

level as a result of deliberate efforts; continued in-

tervention measures are required to maintain the

reduction. Example: diarrhoeal diseases.

Elimination of disease: Reduction to zero of the

incidence of a specified disease in a defined geo-

graphical area as a result of deliberate efforts; con-

tinued intervention measures are required. Example:

neonatal tetanus.

Elimination of infections: Reduction to zero of the

incidence of infection caused by a specific agent in

a defined geographical area as a result of deliberate

efforts; continued measures to prevent re-

establishment of transmission are required. Exam-

ple: measles, poliomyelitis.

Eradication: Permanent reduction to zero of the

worldwide incidence of infection caused by a spe-

cific agent as a result of deliberate efforts; interven-

tion measures are no longer needed. Example:

smallpox.

How synchronized OPV mass campaigns work

Simultaneous administration of OPV within a short pe-

riod interrupts the transmission of wild polio virus by

displacing it from the gut. The effect is enhanced by a

100% vaccine coverage of the population at risk

(children less than 5 years). The result is abrupt interrup-

1

tion of WPV transmission in the community .

Global Polio Eradication Initiative (GPEI)

The Global polio eradication initiative was launched in

1

988. It was made up delegates from 166 member states

who adopted a resolution to eradicate polio world-wide.

It was primarily led by the World Health Organization

(

WHO), the Rotary International, the United States Cen-

ters for Disease Control and Prevention (CDC), and the

United Nations Children’s Fund (UNICEF).

•

7

, 13

:

The objectives of the GPEI include

•

Interruption of wild polio virus

Certification of global polio eradication

Contribution to health system development and

strengthening of routine immunization surveillance

for communicable diseases in a systematic way.

Extinction: The specific infectious agent no longer

exists in nature or in the laboratory. Example: none.

However, there are several other definitions of elimina-

tion and eradication ranging from₀ geographically limited

1

The GPEI has four major strategies for countries af-

fected or at risk of re-infection namely:

definitions to global definitions .

The ultimate aims of public health are disease control,

elimination and eradication. The basic question is when

these aims will be achieved.

•

High routine infant immunization coverage with 4

doses of OPV in the first year of life

Supplementary immunization activities for all under

five children

Optimum surveillance for WPV through reporting

and laboratory testing of all AFP cases in children

less than 15 years.

Why is polio eradicable?

Polio is considered eradicable because:

•

Man is the only reservoir/host.

A long term carrier state is not known to occur .

Effective and cheap vaccine is universally available

•

Targeted (data-driven) “mop-up” campaigns once

WPV is limited to specific focal areas.

1

(

OPV).

GPEI Strategic plan 2010-2012

•

The vaccine (OPV) is easy to administer on mass

basis.

The polio vaccine is relatively stable.

st

In May 2008, the 61 World Health Assembly called for

a new one-year programme of work to replace the earlier

multi-year strategic plan and subsequently, the 2009

Programme of work was developed. Following the im-

plementation of the 2009 GPEI programme of work, a

strategic plan was developed based on lessons learned

from 20 years of experience in polio eradication and

implementation of the 2009 programme of work. This

new plan is to be implemented from 2010-2012 with

definite milestones set (Table 4). The progress is to be

Direct and Indirect effect of OPV (Herd effects)

When adequate number of doses of OPV are adminis-

tered to a population at risk, the immunity so conferred

interrupts transmission in that population. This is known

as the indirect effect of the vaccine, such that any sus-

ceptible individual in that community will no longer be

exposed to the virus and so is protected, though non-

immune (herd protection). Secondly, vaccinated indi-

viduals transmit the vaccine virus to unvaccinated

2

internationally analyzed and graded by experts .

1

9

Table 4 : GPEI global milestones 2010-2013

By mid-2010

By end-2010

By end-2011

By end-2012

By end-2013

Cessation of all

polio outbreaks

with onset in 2009*

Cessation of all

‘re-established’

Poliovirus transmis-

sion**

Cessation of all polio trans-

mission in at least two of the

four endemic countries***

Cessation of all

wild poliovirus

transmission†

Initial validation

of 2012 mile-

stones††

*

validated when six months without a case genetically linked to a 2009 importation (i.e. by end-2010). The target for stopping any

new outbreaks (i.e. with onset in 2010, 2011 or 2012) will be within six months of the confirmation of the index case.

** validated when 12 months without a case genetically linked to the re-established virus (by end-2011).

*** validated when 12 months without a case genetically linked to an indigenous virus (by end-2012); the year-to-year change in

the number of polio cases will be monitored quarterly for each endemic country to guide the assessment of progress towards this

global milestone.

†

epidemiologic region .

validated when 12 months without a case genetically linked to an indigenous virus (by end-2013).

† ‘certification’ will require at least three years of zero polio cases in the presence of appropriate surveillance across an entire

2

1

4

Table 5: WHO Regions certified polio free

WHO Region

Year certified

The Americans (36 countries)

Western Pacific (37 countries)

European Region (countries)

1994

2000*

2002*

*Some countries in these regions have suffered importations after

certification

Fig 1: Number of laboratory-confirmed cases by wild poliovirus (WPV) type or vaccine-derived poliovirus type 2 (VDPV2) and

month of onset, type of supplementary immunization activity (SIA),* and type of vaccine administered in Nigeria, January 2009--

Abbreviations: mOPV1 = monovalent oral polio vaccine (OPV) type 1; mOPV3 = monovalent OPV type 3; tOPV = trivalent OPV; bOPV = biva-

lent OPV.

*

Mass campaign conducted in a short period (days to weeks) during which a dose of OPV is administered to all children aged <5 years, regardless

of previous vaccination history. Campaigns can be conducted nationally or in portions of the country.

2

0

1

However, the current objectives are

Polio Eradication Trends in Nigeria

•

Interrupting wild poliovirus transmission in Asia

Interrupting wild poliovirus transmission in Africa

Enhancing global surveillance and outbreak re-

sponse

In Nigeria, routine surveillance report of AFP cases as-

sociated with faecal excretion of type 2 cVDPV, type 1

and type 3 WPVs from January 2005 to June 2009 were

1

5

studied by Jenkins et al . It revealed that within the

study period there were a total of 2,323 cases of type 1

WPVs, 278 cases of type 2cVDPVs and 1,059 cases of

type 3 WPVs. There were no significant differences in

the clinical severity of paralysis caused by these types of

polioviruses.

•

Strengthening immunization systems

For a WHO region to be certified polio-free, three con-

ditions must be met :

•

8

At least 3 years of no polio case due to WPV

Disease surveillance efforts in countries must meet

international standards

Each country must show capacity to detect, report

and respond to “imported” polio cases.

The progress of polio eradication had been initially

slow, then checkered and retarded by political and socio-

cultural factors in 2003. Following the resurgence of

polio in Nigeria in 2003, and subsequent export of the

virus to 20 other countries, the feasibility of polio eradi-

•

Since 1988, more than 2 billion children around the

world have been immunized against polio, through the

unprecedented cooperation of more than 200 countries

and 20 million volunteers, backed by an international

investment of more than US$ 5 billion .

So far, the following regions have been certified polio-

free: (Table 5)

1

6

cation was brought under serious question . Subse-

quently there was a sudden success leap towards the end

of 2009 followed by uneven progress till date. Fig 1

from CDC summarizes the progress between January

1

17

009 and June 2011 .

2

However, to achieve a global polio-free certification,

laboratory stocks must be contained and safe manage-

ment of WPV in IPV manufacturing sites must be as-

sured.

Table 6 shows the WPV situation worldwide and coun-

try break down as at first week of₈July 2012. The data

1

which was published by the GPEI shows that Nigeria

tops the list and endemic countries contribute more than

9

5% of global burden. The total year-to-date WPV in

Nigeria increased by more than 300% from 2011 to

012.

2

th

Table 6: Wild poliovirus situation worldwide as at 4 July 2012

Total in

Date of most

recent case

Year-to-date 2012

Year-to-date 2011

2

011*

Countries

WPV1

40

WPV3

12

Total

52

10

WPV1

12

WPV3

Total

17

Nigeria

Afghanistan

Pakistan

India

5

1

62

80

198

1

06-Jun-12

29-May-12

22-May-12

13-Jan-11

11-May-12

20-Dec-11

07-Jul-11

22-Dec-11

08-Dec-11

09-Oct-11

03-Aug-11

30-Jul-11

24-Jul-11

23-Jun-11

22-Jan-11

15-Jan-11

10

19

8

2+1W1W3 22

57

1

58

1

Chad

4

82

60

4

3

85

60

4

132

93

5

DR Congo

Angola

Niger

1

5

CAR

4

China

21

3

1

Guinea

Kenya

1

Côte d'Ivoire

Mali

11

4

11

4

36

7

Congo

Gabon

Total

1

73

14

0

88

84

4

226

26

6

252

650

Total in endemic coun-

tries

6

4

9

78

84

341

309

Total outbreak

148

20

168

1

Data in WHO as of 05 Jul 2011 for 2011 data and 03 Jul 2012 for 2012 data

2

1

9

Fig 2a highlights the persisting presence of cVDPVs

in Nigeria. They still constitute a significant proportion

of the total polio cases.

have been responsible for polio outbreaks in several

7

countries including Nigeria, Democratic ₅Republic of

Congo (DRC), Egypt, Haiti and Madagascar .

Experts argue that since OPV from which these reverted

strains are derived currently remains the main stay of the

Polio Eradication Programme (PEP), and realizing that

IPV is too expensive to serve as a substitute in many

developing countries; “it is clear that poliovirus eradica-

tion using the current affordable strategies is unrealis-

2

0

tic” . It has been argued that the huge sum of money

spent on PEP cannot be justified on the basis of disease

burden. They rather advocate that such funds should be

inves₀ted in developing a cheaper non-live polio vac-

2

Note: The difference between total confirmed polio cases and wild virus con-

firmed polio cases is due to circulating vaccine-derived polio virus.

cine .

1

9

The other argument is that polio is largely an asympto-

matic disease and it is estimated that for every single

case of paralytic polio there are about 200 undetected

infections. By the time a response with an SIA is organ-

ized, the disease would have likely spread. Although

man is the only host, chronic polio virus carriage has

been demonstrated in small number of patients with B-

cell deficiency in which polio virus has persisted for

Fig 2b shows the global picture and Africa has the

highest burden.

7

many years .

Additionally and very importantly too, neuro virulent

polio virus has been synthesized de novo in the labora-

2

1

tory and this strongly raises a question as to the view

or concept that the planet can ever be reliably sterilized

from polio virus. With the advent of bioterriosim coun-

tries cannot ignore the possibility of such an agent being

used against them by terrorists. According to Grepkin ,

although the PEP has achieved remarkable success in

the control of the disease, the continued policy towards

the present end-point of polio virus eradication, is unat-

tainable.

Rational arguments

The eradicability of polio has been a subject of debate

especially in recent years. Some have called to question

the rationality or otherwise of the huge sums of fund

spent globally on the Polio Eradication Initiative (PEI)

while proponents have advanced their own reasons for

continuing effort towards the global project. While some

believe polio is not eradicable, others think that even if

it is eradicable, it is of little individual benefit . Yet

others strongly believe it is not only eradicable, but that

eradication is in sight. This group also believes it is of

great public good.

2

0

2

0

Arguments for eradication

On the other hand, some experts see polio eradication as

very feasible from biological point of view. In their

opinion, since there are effective vaccines, just like in

the case of small pox, polio can be eradicated. Indeed,

one of the 3 types of the virus (types) has been eradi-

cated. Additionally 99% reduction in circulation of

WPV worldwide has already been achieved and many

countries and some regions have already eliminated the

virus. The last 1% should be achievable. Only 3 coun-

tries have never interrupted WPV transmission-Nigeria,

Afghanistan and Pakistan. Even in Nigeria, transmission

is only limited to Northeast and Northwestern regions of

the country. All these point to the feasibility of polio

eradication, not only in Nigeria but globally. Before

India achieved certification for elimination, it similarly

had WPV transmission limited to the Uttar Pradesh and

Bihar states and the Indian Government almost gave up

on eradication efforts. However further concentration of

eradication efforts in these areas eventually led to a suc-

cessful interruption of polio transmission. This is inspite

of lower immune response to tOPV in South East Asia

Arguments against eradication

That small pox was successfully eradicated does not

necessarily imply that other diseases will be eradicated

also. Epidemiologists have argued that some diseases,

for which global eradication programs have been

launched in the past, are not eradicable. This is because

diseases that have non-human reservoirs could be re-

introduced following a presumed eradication. This ap-

plies to malaria and yellow fever₀whose past global

2

eradication programmes have failed .

2

0

Polio vaccine is not as effective as small pox vaccine

and after 3 doses of OPV, full protection is not guaran-

teed as vaccines are not equally effective against all 3

7

strains of the virus . The live vaccine virus on rare occa-

sions can revert to neuro-virulence and cause disease

similar to that caused by the wild polio virus. Some have

described this as using fire to fight fire. These cVDPV

2

than in Africa .

2

Although polio eradication has been said to divert lim-

ited financial and human resources away from primary

•

The continuing cases of VAPP resulting from the

reverted VDPV.

Mal-orientation of communities, politicians and

health workers.

Politicization of health issues.

Very large population and high population growth

rate with cultural, religious and geographical

barriers.

Funding short-falls and poor accountability frame-

work.

2

health care , a world free of the need for polio vaccine

would save₁₆U_,₂₃SD81.5 billion per year in immunization

costs alone . Additionally, apart from financial sav-

ings and prevention of crippling effects of polio, polio

eradication also has intangible and co-incidental bene-

fits. These include stronger immunization and surveil-

lance systems, well established global laboratory net-

work, millions of tr₂a₄_,i₂n₅ed health workers and strong ad-

vocacy movements . The option of controlling rather

than eradicating polio (by means of routine immuniza-

tion only) has been shown in a modeling study to poten-

tially result in great cumulative cost and far larger num-

•

With elimination of poliovirus in India, Nigeria stands

out as the single most important country now in the

global polio eradication agenda.

1

6,26

.

ber of cases

The Way Forward

Prospects

•

The current use of mOPV 1, mOPV 3, bOPV and

tOPV must continue but must be guided by sound

scientific advice from experts. However, the use of

mOPV and bOPV must be balanced with the find-

ings of waning population immunity against type 2

which predisposes to susceptibility to type 2

cVDPV. Yet, it must be born in mind that tOPV

which is the only OPV against type 2 has much

lower effectiveness against the commonest type 1 in

the country. This calls for a delicate balance in the

use of these vaccines and for further research.

It also draws the country’s attention towards plan-

ning to explore the place of IPV in the future which

will totally eliminate the threat of cVDPVs and

VAPP.

There is a very urgent need to raise routine immuni-

zation coverage to at least 95%. This coverage

should not only be achieved nationally but also sub-

nationally in all Local Government Areas (LGAs)

and wards.

Additionally SIAs should be more effective with

realistic coverage approaching 100%.

Focused and effective mop up activities in special

areas.

The prospects for polio eradication in Nigeria and by

extension globally are high. These are based on:

•

The antecedent of not just small pox eradication but

also progress so far made in polio eradication in

Nigeria, India and the currently polio-free countries

and regions.

The huge financial and human resources the country

is able to mobilize from the Federal, State and Local

Governments; as well as from International and

local partners.

Already existing health care structure, especially for

immunization, established by the National Pro-

gramme on Immunization (NPI) and improved upon

by the National Healthcare Development Agency

•

(

NPHCDA).

•

High level of community and political awareness

already achieved.

•

A level of political and community commitment

Skilled and experienced personnel-both full time

and adhoc health workers.

•

Massive global technical, political and financial

support especially based on the fact that polio eradi-

cation is a global initiative and not just a Nigerian

programme.

Continuing immunogenicity, epidemiological and

communication studies are required to monitor

trends and develop area-specific strategies.

Targeted mop ups and penetration of conflict areas

are required to eliminate reservoirs of the virus.

Re-orientation of health workers, adhoc personnel,

policy makers and the community.

Challenges

•

Although the prospects are high, the challenges are enor-

mous and require total commitment and focused strate-

gies to overcome. These challenges include;

•

Low and differential routine and supplemental im-

munization coverages below the threshold required

for interruption of transmission. These immunity

gaps allow viruses to persist in smaller areas and

Effective advocacy to politicians and massive social

and community mobilization.

Targeted communication strategies aimed at over

coming cultural, religious and political barriers.

Also improvement in community participation

Intensive and special arrangement for adequate cov-

erage of hard to reach areas and migrant popula-

tions.

Urgent strengthening of AFP surveillance in all

communities in all LGAs.

Country / government ownership of PEP as well as

routine immunization programme with full imple-

mentation of the accountability framework.

2

population sub-groups .

•

Relatively lower effectiveness of tOPV resulting in

low immunity especially against type 1 virus in

vaccinated population . Type 1 is the commonest

in Nigeria.

The emergence of type 2 cVDPVs outbreaks in Ni-

geria whose transmissibility, pathogenicity and

disease severity are similar to those of type 2 WPV.

Type 2 WPV has been eliminated globally since

•

1

5

•

1

999.

2

3

Conclusion

The future

Small pox was eradicated and polio is biologically eradi-

cable. The global eradication effort has already achieved

over 99% success with elimination certification in many

countries and WHO regions. Even re-infections have

been successfully and promptly eliminated in previously

certified countries. India whose polio eradication history

is similar to Nigeria’s in several ways has eventually

achieved elimination certification. Nigeria has also

achieved giant strides (90% success) since the PEP in

the country. Therefore the prospects for polio eradica-

tion in Nigeria are high but the current challenges re-

quire urgent, sustained and focused attention so as to

shorten the journey from now to eradication time.

Even after WPV transmission is interrupted and elimi-

nated globally. The problem of reverted neurovirulent

vaccine virus would remain to be addressed. As long as

live OPV remains in use, Nigeria and indeed, the world

cannot relax. Nigeria and the global community must

plan for a switch from OPV to IPV and then complete

stoppage of OPV production. Many countries have al-

ready stopped the use of OPV while others are at the

OPV-IPV transition phase. While the call for a cheaper

IPV continues, Nigeria must not wait but should begin

to plan for financing of the switch. Local vaccine pro-

duction is a potentially cheaper option.

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