Elsevier

The Lancet

Volume 369, Issue 9570, 21–27 April 2007, Pages 1356-1362
The Lancet

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Protective efficacy of a monovalent oral type 1 poliovirus vaccine: a case-control study

https://doi.org/10.1016/S0140-6736(07)60531-5Get rights and content

Summary

Background

A high-potency monovalent oral type 1 poliovirus vaccine (mOPV1) was developed in 2005 to tackle persistent poliovirus transmission in the last remaining infected countries. Our aim was to assess the efficacy of this vaccine in India.

Methods

We estimated the efficacy of mOPV1 used in supplementary immunisation activities from 2076 matched case-control pairs of confirmed cases of poliomyelitis caused by type 1 wild poliovirus and cases of non-polio acute flaccid paralysis in India. The effect of the introduction of mOPV1 on population immunity was calculated on the basis of estimates of vaccination coverage from data for non-polio acute flaccid paralysis.

Findings

In areas of persistent poliovirus transmission in Uttar Pradesh, the protective efficacy of mOPV1 was estimated to be 30% (95% CI 19–41) per dose against type 1 paralytic disease, compared with 11% (7–14) for the trivalent oral vaccine. 76–82% of children aged 0–23 months were estimated to be protected by vaccination against type 1 poliovirus at the end of 2006, compared with 59% at the end of 2004, before the introduction of mOPV1.

Interpretation

Under conditions where the efficacy of live-attenuated oral poliovirus vaccines is compromised by a high prevalence of diarrhoea and other infections, a dose of high-potency mOPV1 is almost three times more effective against type 1 poliomyelitis disease than is trivalent vaccine. Achieving high coverage with this new vaccine in areas of persistent poliovirus transmission should substantially improve the probability of rapidly eliminating transmission of the disease.

Introduction

By early 2004, the transmission of indigenous wild poliovirus had been interrupted in all but six countries of the world as a result of a concerted international eradication effort.1 In four of these countries—Nigeria, Niger, Pakistan, and Afghanistan—sustained transmission was the result of a failure to immunise a sufficiently high proportion of children against poliomyelitis.2 However, In India and Egypt, poliovirus transmission persisted despite immunisation coverage with four doses of the trivalent oral poliovirus vaccine of more than 90% among children aged less than 5 years.3, 4

In recognition of the grave threat that persistent transmission in India and Egypt posed to the Global Polio Eradication Initiative, the programme's international oversight body urgently reviewed a range of options in October, 2004, to enhance the effectiveness of vaccination in these areas. By that time, transmission of wild type 2 poliovirus had been interrupted worldwide and type 3 poliovirus had been eliminated in Egypt and all but one state of India. Consequently, the Advisory Committee on Polio Eradication recommended the rapid development, licensing, and introduction of a new monovalent oral type 1 poliovirus vaccine (mOPV1).1 This new vaccine possesses five times the potency of licensed monovalent vaccines used in the early 1960s (1×106 median cell culture infective doses [CCID50] vs 200 000 CCID50 per dose).5 Through an extraordinary public-private development effort this new mOPV1 was licensed by April, 2005, in India and Egypt and used in mass polio immunisation campaigns in India (April, 2005) and Egypt (June, 2005).6, 7

The efficacy of mOPV1 has major implications for international public health. The Global Polio Eradication Initiative has invested US$5 billion in eradication over a 20-year period and a key role is now proposed for monovalent vaccines in the strategic approach to interrupting the transmission of remaining indigenous wild poliovirus and managing the risks of re-emergent transmission of poliovirus after global certification of eradication.8, 9

Especially important to the programme is the effectiveness of the monovalent vaccine under field conditions of poor sanitation and high population density, where a high prevalence of diarrhoeal disease and other infections have been shown to interfere with the efficacy of trivalent oral poliovirus vaccine as well as to favour the transmission of wild poliovirus.10, 11, 12 In Egypt, no indigenous strain of wild poliovirus has been detected since the introduction of mOPV1.6 In India, however, a polio outbreak in 2006 allowed us to study the efficacy of this new vaccine under field conditions. Our aim was to determine the protective efficacy of mOPV1 in India and explore the consequent implications of mOPV1 for global polio eradication and post-eradication risk management.

Section snippets

Patients and procedures

Since the introduction of mOPV1 use in India in 2005, vaccination efforts have focused on the northern states of Uttar Pradesh—where over 80% of all type 1 cases of poliomyelitis in India in 2006 occurred—and Bihar. Frequent rounds of vaccination with mOPV1 have been interspersed with use of trivalent vaccine to maintain immunity to type 3 poliovirus. In the few districts with continued reporting of type 3 poliomyelitis, monovalent vaccine against type 3 (mOPV3) has also been used in up to two

Results

122 173 cases of acute flaccid paralysis were identified. Of these, 2580 did not have two adequate stool samples and had residual paralysis compatible with poliomyelitis and were thus excluded from the analysis; a further 5773 cases did not report the number of vaccine doses received and were also excluded. 4966 cases of type 1 poliomyelitis had complete dose information for the entire study period; of these, 2076 were matched with suitable controls (table 1). The age distribution of matched

Discussion

Our results show that, in the state of Uttar Pradesh, the monovalent vaccine is about three times more likely to result in a protective immune response against type 1 paralytic poliomyelitis than is the trivalent vaccine, irrespective of the assumption about routine immunisation. This increased efficacy is probably caused by the absence of interference between the three Sabin vaccine strains.20 Even balanced formulations of trivalent poliovirus vaccines tend to result in preferential infection

References (23)

  • H Graf

    Manufacturing and supply of monovalent oral polio vaccines

    Biologicals

    (2006)
  • Conclusions and recommendations of the Ad Hoc Advisory Committee on Poliomyelitis Eradication, Geneva, 21–22 September 2004

    Wkly Epidemiol Rec

    (2004)
  • Progress towards global eradication of poliomyelitis, 2003 and January–April 2004

    Wkly Epidemiol Rec

    (2004)
  • Progress towards poliomyelitis eradication in Egypt, January 2003 to July 2004

    Wkly Epidemiol Rec

    (2004)
  • Progress towards poliomyelitis eradication in India, 2003

    Wkly Epidemiol Rec

    (2004)
  • VM Caceres et al.

    Sabin monovalent oral polio vaccines: review of past experiences and their potential use after polio eradication

    Clin Infect Dis

    (2001)
  • Conclusions and recommendations of the Advisory Committee on Poliomyelitis Eradication, Geneva, 11–12 October 2005

    Wkly Epidemiol Rec

    (2005)
  • RB Aylward et al.

    Risk management in a polio-free world

    Risk Anal

    (2006)
  • RB Aylward et al.

    OPV cessation - the final step to a “polio-free” world

    Science

    (2005)
  • NC Grassly et al.

    New strategies for the elimination of polio from India

    Science

    (2006)
  • Factors affecting the immunogenicity of oral poliovirus vaccine—a prospective evaluation in Brazil and the Gambia

    J Infect Dis

    (1995)
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