Immunogenicity of Inactivated and Live Polio Vaccines
Condition: Poliomyelitis
MeSH terms: Poliomyelitis
Study type: Interventional
Phase: Phase 3

Summary: 
      This study is an open-label phase III randomized clinical trial that would compare
      immunogenicity after receiving one of five different combinations of polio vaccines. Infants
      will be enrolled and randomized at 6 weeks of age to one of five different arms:

      A) Three doses of trivalent oral poliovirus vaccine (tOPV) at 6, 10 and 14 weeks of age B)
      Three doses of bivalent OPV (bOPV) at 6, 10 and 14 weeks of age C) Two doses of intramuscular
      (IM) inactivated poliovirus vaccine (IPV) at 6 and 14 weeks of age D) Two doses of
      intra-dermal (ID) fractional IPV (f-IPV) at 6 and 14 weeks of age E) Sequential
      administration of ID f-IPV at 6 and 14 weeks of age with bOPV at 10 weeks of age To assess
      the immunogenicity of each study vaccine and vaccination schedule, antibody titers against
      poliovirus types 1, 2 and 3 will be determined in sera extracted from blood collected before
      (at 6 weeks of age) and after receiving 3 doses of study vaccine (18 weeks of age).
      Seroconversion will be defined as a titer 4-fold higher than the expected fall in maternally
      derived antibodies, assuming a half-life of 28 days. The initial antibody titer at 6 weeks of
      age will be used as the starting point for the expected decline in maternal antibody.

      This study will compare the immunogenicity of:

        1. Sequential dose of intra-dermal f-IPV and bOPV to bOPV alone administered at 6, 10 and
           14 weeks of age

        2. tOPV to bOPV administered at 6,10 and 14 weeks of age

        3. IM IPV to ID f-IPV administered at 6 and 14 weeks of age The answer to these questions
           will guide the global polio eradication program in designing new routine immunization
           schedule for children that eliminates the risks of paralysis due to vaccine derived
           poliovirus (VDPV) from type 2 vaccine poliovirus.
    

Detailed description: 
      Global polio eradication initiative (GPEI)

      In 1988, the World Health Assembly adopted the resolution of polio eradication by 2000. This
      launched the Global Polio Eradication Initiative (GPEI), spearheaded by World Health
      Organization (WHO), Rotary International, US Centers for Disease Control and Prevention (CDC)
      and United Nations Children's Emergency Fund (UNICEF). The major strategies to achieve polio
      eradication included: 1) provision of 3-4 doses of tOPV to young infants through routine
      immunization programs; 2) provision of additional doses to all children < 5 years of age
      through immunization campaigns (supplementary immunization activities or SIAs); 3)
      surveillance for all cases of acute flaccid paralysis in children <15 years of age; and 4)
      mop-up immunizations campaigns following the detection of poliovirus circulation.

      OPV was the vaccine of choice for polio eradication due to its low cost, ease of
      administration, ability to induce intestinal immunity and community spread to aid in
      induction of immunity.

      Limitations of trivalent oral polio vaccine (tOPV)

      tOPV is a mixture of all three types of polioviruses and there is interference among the
      strains during intestinal replication. Type 2 especially interferes with uptake of types 1
      and 3. tOPV has higher seroconversion rates in industrialized countries compared to that in
      developing countries. A study conducted in Brazil and Gambia reported tOPV seroconversion
      rates of 85% for Type 1, 94% for type 2 and 68% for Type 3 with three doses of tOPV. Compared
      to monovalent OPVs, trivalent OPV has lower seroconversion rates. To address concerns of
      lower efficacy of tOPV for type 1 and type 3 compared to monovalent vaccines, monovalent
      vaccines were re-introduced in the polio eradication initiative. Monovalent OPVs are more
      immunogenic than tOPV. In India, compared to two doses of tOPV given at birth and after 30
      days, type-specific seroconversion was significantly higher with two doses of mOPV1 (90% vs.
      63%) and mOPV3 (84% vs. 52%). In South Africa, compared to one dose of tOPV given at birth,
      type-specific seroconversion was significantly higher with one dose of mOPV1 (73% vs. 39%)
      and mOPV3 (58% vs. 21%).

      While the higher immunogenicity of monovalent vaccines compared to trivalent vaccine is
      highly desirable especially in the presence of a poliovirus outbreak caused by one antigenic
      type, the monovalent vaccines increase the complication in vaccine selection. Wild type 2
      poliovirus was eradicated in 1999 and at the present time there is global circulation of wild
      poliovirus Type 1 and 3. Weak routine immunization with poor immunization coverage will lead
      to immunity gaps against all three types of polioviruses. In the presence of Type 1
      poliovirus outbreak in a country with weak routine immunization, use of a monovalent Type 1
      poliovirus vaccine will contribute to reducing the immunity gap to Type 1 poliovirus,
      however, this would not address the existing immunity gap to Type 3 poliovirus and vice
      versa. Additionally, in the presence of an outbreak of Type 1 and Type 3 polioviruses,
      vaccine selection becomes further complicated. To address these concerns, bivalent OPV
      (bOPV), mixture of type 1 and type 3, was introduced in the polio eradication program in
      2010. The only published clinical trial on bOPV reported that two doses of bOPV given at
      birth and 30 days later was comparable in immunogenicity to two doses of mOPV1 and mOPV3 and
      significantly better than two doses of tOPV.

      Oral poliovirus vaccines are live attenuated viral vaccines and the vaccine virus in OPV can
      mutate and acquire neurovirulence causing paralysis either due to vaccine-associated
      paralytic polio (VAPP) or due to circulating vaccine-derived polioviruses (cVDPV), in which
      the attenuated vaccine virus not only acquires the ability to cause paralysis but can also
      circulate similar to wild poliovirus (WPV). The potential of vaccine virus to acquire
      neurovirulence and cause paralytic poliomyelitis is incompatible with eradication of polio.
      Therefore, polio eradication will require eventual cessation of all OPVs.

      The last case of type 2 WPV (WPV2) was reported in 1999 in India. Type 2 vaccine virus in
      tOPV is most likely to cause cVDPVs and over 80% of cVDPVs over the past decade have been
      cVDPV2. Of the estimated 250-500 annual VAPP cases almost 40% are due to type 2. Thus, with
      the eradication of WPV2 it is imperative to prioritize removal of type 2 containing OPV.

      Role of bivalent oral polio vaccine (bOPV) and inactivated polio vaccine (IPV)

      The licensing and availability of bivalent OPV (bOPV) containing type 1 and 3 offers the
      option of an OPV that does not contain OPV2. No studies have assessed the immunogenicity of
      bOPV when administered in the Expanded Program on Immunization (EPI) schedule of 6, 10 and 14
      weeks of age. Additionally, no studies have compared the immunogenicity of bOPV to that of
      tOPV when administered at 6, 10 and 14 weeks of age. Thus, this comparison has been proposed
      in this study with inclusion of a bOPV and a tOPV arm.

      At the same time, while a switch in routine immunization from tOPV to bOPV has been proposed,
      there are significant challenges that need to be addressed prior to implementing this
      possible switch. Removing type 2 OPV from routine immunization will rapidly increase the
      proportion of population susceptible to type 2. This is turn could facilitate the
      transmission of cVDPV2 from countries experiencing an outbreak of cVDPV2. Ideally, all cVDPV2
      outbreaks will need to be stopped prior to replacement of tOPV with bOPV. Equally important
      is the need for synchronization of cessation of type 2 OPV globally or regionally to reduce
      the risk of cVDPV2 importation from countries that continue to use tOPV. The IPV working
      group of Strategic Advisory Group of Experts on Immunization (SAGE) has endorsed a set of
      necessary pre-requisites for type 2 OPV cessation and these include: formal validation of
      absence of WPV2, interruption of cVDPV2 prior to OPV2 cessation, laboratory containment of
      WPV2, availability of sufficient bOPV for the switch and stockpile of monovalent oral
      vaccines (mOPV) for outbreak response. At the same time, there is a clear recognition that it
      would take few more years to achieve the necessary pre-requisites while the balance has
      already shifted from benefit to risk for type 2 OPV.

      Another potential option is to switch from tOPV to IPV but IPV is substantially more
      expensive than OPV and is not as immunogenic as OPV in inducing mucosal immunity. Hence, the
      polio eradication program is exploring ways to make IPV affordable for polio eradication that
      include reducing the number of IPV doses, reducing the antigen content for each dose,
      manufacturing IPV in developing countries and optimizing other production processes. One of
      the possible methods of reducing the antigen content of each dose of IPV is to use a
      fractional injection of IPV (f-IPV) of one-fifth of standard IPV dose given intra-dermally.
      Compared to intra-muscular injection of IPV, it appears that f-IPV has sub-optimal
      immunogenicity when administered at 6, 10 and 14 weeks of age (EPI schedule) [ID f-IPV vs IM
      IPV: Type 1: 53% vs 89%; Type 2: 85% vs 96%; Type 3: 69% vs 99%] though the immunogenicity is
      comparable when administered at 2, 4 and 6 months of age [ID f-IPV vs IM IPV: Type 1: 97% vs
      100%; Type 2: 96% vs 100%; Type 3: 98% vs 100%]. Prior studies have reported that the
      interval between multiple doses of IPV plays an important role in the immunogenicity of IPV
      11. A study conducted in Cuba reported seroconversion rates of 94%, 83% and 100% for Type 1,
      2 and 3 respectively with 3 doses of IM IPV administered at 6, 10 and 14 weeks of age. These
      seroconversion rates were similar to seroconversion observed after 2 doses of IPV
      administered at 8 and 16 weeks of age (Type 1: 90%; Type 2: 89%; Type 3: 90%). Hence, it is
      hypothesized that the 1-month interval between the 3 doses in EPI schedule is a major
      contributor in the sub-optimal immunogenicity of f-IPV compared to the immunogenicity
      reported with the 2, 4 and 6 month schedule, which has a 2-month interval between doses. As a
      result in this study the immunogenicity of IM IPV and ID f-IPV administered at 6 and 14 weeks
      is being assessed where the interval between doses is 2 months.

      Justification for this study

      There are significant risks associated with switching from tOPV to bOPV in routine
      immunization. IM IPV is substantially more expensive than tOPV and not as immunogenic in
      inducing mucosal immunity. These are the principal reasons that prevent use of IM IPV in EPI
      schedule. ID f-IPV has sub-optimal immunogenicity when used in EPI schedule. Therefore, the
      polio program needs to test the immunogenicity of combination of poliovirus vaccines as this
      could potentially address concerns of risks of using bOPV alone and suboptimal immunogenicity
      of ID f-IPV. Prior studies have shown that IPV and OPV given together as a combination or
      sequentially with OPV followed by IPV achieves a higher seroconversion than IPV or OPV alone
      and the mucosal immunity induced by combined IPV and OPV is similar to that induced by OPV.
      However, seroconversion of sequential f-IPV and bOPV has not yet been determined.
      Consequently, this study will assess the immunogenicity of a sequential dose of f-IPV and
      bOPV. Combining bOPV and f-IPV in an immunization schedule has multiple advantages. Firstly,
      f-IPV will aid in development of Type 2 immunity. Secondly, bOPV combined with f-IPV is
      likely to be more immunogenic than f-IPV alone. Finally, bOPV is likely to contribute
      substantially to development of Type 1 and 3 mucosal immunity.

      Rationale for the location of the study and the study population

      Polio immunization in Bangladesh is provided through the Expanded Program on Immunization to
      achieve high routine coverage with 3 doses of tOPV in infants younger than 12 months and
      through National Immunization Days that are usually conducted twice a year. The 3 doses of
      tOPV through routine immunization services is administered to infants at 6, 10 and 14 weeks
      of age and WHO/UNICEF estimate coverage of 95% for 2010 with three doses of polio vaccine.
      With these strategies, Bangladesh interrupted endemic transmission in 2000 and has
      successfully prevented outbreaks or re-establishment of circulation following importations
      from neighboring India. With the interruption of polio transmission, Bangladesh is at a
      critical juncture where it needs to consider steps to reduce the risks associated with
      emergence of VDPV2. Therefore, it is advantageous to test a potential new combination of
      existing polio vaccines to reduce risks of VDPV2 emergence in Bangladesh. The results of the
      study will be applicable in Bangladesh as well as important for the global polio eradication
      program. ICDDR, B has long-standing expertise in conducting clinical trials and has conducted
      a polio clinical trial in the proposed site Mirpur, Dhaka. This study reported a
      seroconversion of 86% for Type1, 97% for Type 2 and 75% for Type 3 after 3 doses of tOPV at
      6, 10 and 14 weeks of age.
    

Intervention name(s): Group A: Trivalent Oral Polio Vaccine; Group B: Bivalent Oral Polio Vaccine; Group C: Inactivated Polio Vaccine; Group D: fractional IPV (f-IPV); Arm E: f-IPV and bOPV
Intervention type(s): Biological; Biological; Biological; Biological; Biological
Intervention description(s): Group A will receive 3 doses of trivalent oral polio vaccine (tOPV) at 6, 10 and 14 weeks of age. A challenge dose of tOPV will be administered at 18 weeks of age.; Group B will receive 3 doses of bivalent oral polio vaccine (bOPV) at 6, 10 and 14 weeks of age. A challenge dose of tOPV will be administered at 18 weeks of age.; Group C will receive 2 doses of inactivated polio vaccine (IPV) at 6 and 14 weeks of age. IPV will be administered intramuscularly using standard needle and syringe. A challenge dose of tOPV will be administered at 18 weeks of age.; Group D will receive 2 doses of fractional inactivated polio vaccine (f-IPV) at 6 and 14 weeks of age. f-IPV (one-fifth dose of IPV) will be administered intradermally using MicroJet 600 microneedle hub by NanoPass Technologies. A challenge dose of tOPV will be administered at 18 weeks of age.; Group E will receive 2 doses of f-IPV at 6 and 14 weeks of age with bOPV at 10 weeks of age. f-IPV will be administered intradermally using MicroJet 600 microneedle hub by NanoPass Technologies. A challenge dose of tOPV will be administered at 18 weeks of age.
Intervention MeSH terms: Vaccines
Allocation: Randomized
Intervention model: Parallel Assignment
Masking: None (Open Label)
Primary purpose: Prevention
Keywords: Polio; Inactivated polio vaccine; oral polio vaccine; vaccine trial