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Inactivated poliovirus vaccine (IPV) introduction and phased oral poliovirus vaccine (OPV) cessation are essential for eradication of polio. Healthy 6-week old infants in Bangladesh were randomized to one of five study arms: receipt of trivalent OPV (tOPV) or bivalent OPV (bOPV) at ages 6, 10 and 14 weeks, intramuscular IPV or intradermal one-fifth fractional dose IPV (f-IPV) at ages 6 and 14 weeks, or f-IPV at ages 6 and 14 weeks with bOPV at age 10 weeks (f-IPV/bOPV). All participants received tOPV at age 18 weeks. Of 975 infants randomized, 95% (922) completed follow-up. Type 1 seroconversion after 3 doses at 6, 10 and 14 weeks was higher with bOPV compared with tOPV (99% vs 94%, p=0.019). Seroconversions to types 1 and 3 after 2 IPV doses at ages 6 and 14 weeks were no different than after 3 doses of tOPV or bOPV at ages 6, 10 and 14 weeks. A priming response, seroconversion 1 week after IPV at 14 weeks among those who did not seroconvert after IPV at 6 weeks, was observed against poliovirus types 1, 2 and 3 in 91%, 84% and 97%, respectively. Compared with IPV, f-IPV failed non-inferiority tests for seroconversion with 1 or 2 doses and priming after 1 dose. The findings demonstrate considerable priming with IPV at age 6 weeks, comparable immunogenicity of tOPV and bOPV, and inferior immunogenicity of one-fifth f-IPV compared with IPV. If IPV induced priming at age 6 weeks is similar to that at age 14 weeks, IPV could be administered at a younger age and possibly with a higher coverage.

The eradication of poliovirus remains a global health priority, with inactivated polio vaccines (IPVs) playing a pivotal role in immunization strategies. Over the past decades, advancements in IPV production have focused on optimizing safety, efficacy, and immunogenicity while addressing vaccine production and logistical challenges. This paper discusses a novel IPV candidate, ultra IPV[sup.TM] , which departs from conventional formalin inactivation and uses a modern ultraviolet C (UVC) inactivation technology that includes a powerful antioxidant that protects virus epitopes from damage during and after irradiation. The potential of UVC inactivation to maintain structural integrity and immunogenicity of viral antigens, while circumventing safety issues with conventional vaccines, could bolster global polio eradication efforts and holds promise for applications to numerous other viral pathogens. Wistar rats were immunized with three dosages of ultra IPV[sup.TM] , IPOL[sup.R] , or vehicle alone. Immune responses were analyzed by whole-virus ELISA and antiviral neutralizing responses. Toxicity was analyzed primarily by increases in body weight and cytokine ELISA. Tolerability was analyzed by gross pathological and histological examinations. ultra IPV[sup.TM] was determined to be immunogenic and non-toxic. No pathological or histological abnormalities related to the vaccine were observed. The data suggest that ultra IPV[sup.TM] is immunogenic and well-tolerated in rats.

The World Health Organisation Western Pacific Region countries were declared free of polio in 2000 until a polio outbreak involving 305 cases occurred in Indonesia in 2006. It was not until 2014 that the World Health Organisation South East Asia region was officially declared polio-free again. However, in February 2019, the Global Polio Eradication Initiative announced a new circulating vaccine-derived poliovirus outbreak in the Papua province of Indonesia. To make matter worse, the outbreak responses were tardy and led to transmission among migrating communities to other cities. The pressing regional issues of polio outbreak caused by circulating vaccine-derived poliovirus and use of oral polio vaccine have not been well presented. Our letter highlighted the suboptimal outbreak responses as well as the necessity of cross-border vaccination to curb continued poliovirus transmission.

The polio eradication endgame strategic plan calls for the sequential removal of Sabin poliovirus serotypes from the trivalent oral poliovirus vaccine (tOPV), starting with type 2, and the introduction of ≥1 dose of inactivated poliovirus vaccine (IPV), to maintain an immunity base against poliovirus type 2. The global removal of oral poliovirus type 2 was successfully implemented in May 2016. However, IPV supply constraints has prevented introduction in 21 countries and led to complete stock-out in >20 countries. We conducted a literature review and contacted corresponding authors of recent studies with fractional-dose IPV (fIPV), one-fifth of intramuscular dose administered intradermally, to conduct additional type 2 immunogenicity analyses of two fIPV doses compared with one full-dose IPV. Four studies were identified that assessed immunogenicity of two fIPV doses compared to one full-dose IPV. Two fractional doses are more immunogenic than 1 full-dose, with type 2 seroconversion rates improving between absolute 19–42% (median: 37%, p<0.001) and relative increase of 53–125% (median: 82%), and antibody titer to type 2 increasing by 2–32-fold (median: 10-fold). Early age of administration and shorter intervals between doses were associated with lower immunogenicity. Overall, two fIPV doses are more immunogenic than a single full-dose, associated with significantly increased seroconversion rates and antibody titers. Two fIPV doses together use two-fifth of the vaccine compared to one full-dose IPV. In response to the current IPV shortage, a schedule of two fIPV doses at ages 6 and 14weekshas been endorsed by technical oversight committees and has been introduced in some affected countries.

AbstractVaccine-derived polioviruses (VDPVs) can emerge from Sabin strain poliovirus serotypes 1, 2, and 3 contained in oral poliovirus vaccine (OPV) after prolonged person-to-person transmission where population vaccination immunity against polioviruses is suboptimal. VDPVs can cause paralysis indistinguishable from wild polioviruses and outbreaks when community circulation ensues. VDPV serotype 2 outbreaks (cVDPV2) have been documented in The Democratic Republic of the Congo (DRC) since 2005. The nine cVDPV2 outbreaks detected during 2005–2012 were geographically-limited and resulted in 73 paralysis cases. No outbreaks were detected during 2013–2016. During January 1, 2017–December 31, 2021, 19 cVDPV2 outbreaks were detected in DRC. Seventeen of the 19 (including two first detected in Angola) resulted in 235 paralysis cases notified in 84 health zones in 18 of DRC’s 26 provinces; no notified paralysis cases were associated with the remaining two outbreaks. The DRC-KAS-3 cVDPV2 outbreak that circulated during 2019–2021, and resulted in 101 paralysis cases in 10 provinces, was the largest recorded in DRC during the reporting period in terms of numbers of paralysis cases and geographic expanse. The 15 outbreaks occurring during 2017–early 2021 were successfully controlled with numerous supplemental immunization activities (SIAs) using monovalent OPV Sabin-strain serotype 2 (mOPV2); however, suboptimal mOPV2 vaccination coverage appears to have seeded the cVDPV2 emergences detected during semester 2, 2018 through 2021. Use of the novel OPV serotype 2 (nOPV2), designed to have greater genetic stability than mOPV2, should help DRC’s efforts in controlling the more recent cVDPV2 outbreaks with a much lower risk of further seeding VDPV2 emergence. Improving nOPV2 SIA coverage should decrease the number of SIAs needed to interrupt transmission. DRC needs the support of polio eradication and Essential Immunization (EI) partners to accelerate the country’s ongoing initiatives for EI strengthening, introduction of a second dose of inactivated poliovirus vaccine (IPV) to increase protection against paralysis, and improving nOPV2 SIA coverage.

The Immunization Systems Management Group (IMG) was established as a time-limited entity, responsible for the management and coordination of Objective 2 of the Polio Eradication and Endgame Strategic Plan. This objective called for the introduction of at least 1 dose of inactivated polio vaccine (IPV) into the routine immunization programs of all countries using oral polio vaccine (OPV) only. Despite global vaccine shortages, which limited countries' abilities to access IPV in a timely manner, 105 of 126 countries using OPV only introduced IPV within a 2.5-year period, making it the fastest rollout of a new vaccine in history. This achievement can be attributed to several factors, including the coordination work of the IMG; high-level engagement and advocacy across partners; the strong foundations of the Expanded Programme on Immunization at all levels; Gavi, the Vaccine Alliances vaccine introduction experiences and mechanisms; innovative approaches; and proactive communications. In many ways, the IMG's work on IPV introduction can serve as a model for other vaccine introductions, especially in an accelerated context.

The eradication of poliovirus remains a global health priority, with inactivated polio vaccines (IPVs) playing a pivotal role in immunization strategies. Over the past decades, advancements in IPV production have focused on optimizing safety, efficacy, and immunogenicity while addressing vaccine production and logistical challenges. This paper discusses a novel IPV candidate, ultraIPVTM, which departs from conventional formalin inactivation and uses a modern ultraviolet C (UVC) inactivation technology that includes a powerful antioxidant that protects virus epitopes from damage during and after irradiation. The potential of UVC inactivation to maintain structural integrity and immunogenicity of viral antigens, while circumventing safety issues with conventional vaccines, could bolster global polio eradication efforts and holds promise for applications to numerous other viral pathogens. Wistar rats were immunized with three dosages of ultraIPVTM, IPOLR, or vehicle alone. Immune responses were analyzed by whole-virus ELISA and antiviral neutralizing responses. Toxicity was analyzed primarily by increases in body weight and cytokine ELISA. Tolerability was analyzed by gross pathological and histological examinations. ultraIPVTM was determined to be immunogenic and non-toxic. No pathological or histological abnormalities related to the vaccine were observed. The data suggest that ultraIPVTM is immunogenic and well-tolerated in rats.

In 2015, the Global Commission for the Certification of Polio Eradication certified the eradication of type 2 wild poliovirus, 1 of 3 wild poliovirus serotypes causing paralytic polio since the beginning of recorded history. This milestone was one of the key criteria prompting the Global Polio Eradication Initiative to begin withdrawal of oral polio vaccines (OPV), beginning with the type 2 component (OPV2), through a globally synchronized initiative in April and May 2016 that called for all OPV using countries and territories to simultaneously switch from use of trivalent OPV (tOPV; containing types 1, 2, and 3 poliovirus) to bivalent OPV (bOPV; containing types 1 and 3 poliovirus), thus withdrawing OPV2. Before the switch, immunization programs globally had been using approximately 2 billion tOPV doses per year to immunize hundreds of millions of children. Thus, the globally synchronized withdrawal of tOPV was an unprecedented achievement in immunization and was part of a crucial strategy for containment of polioviruses. Successful implementation of the switch called for intense global coordination during 2015–2016 on an unprecedented scale among global public health technical agencies and donors, vaccine manufacturers, regulatory agencies, World Health Organization (WHO) and United Nations Children's Fund (UNICEF) regional offices, and national governments. Priority activities included cessation of tOPV production and shipment, national inventories of tOPV, detailed forecasting of tOPV needs, bOPV licensing, scaling up of bOPV production and procurement, developing national operational switch plans, securing funding, establishing oversight and implementation committees and teams, training logisticians and health workers, fostering advocacy and communications, establishing monitoring and validation structures, and implementing waste management strategies. The WHO received confirmation that, by mid May 2016, all 155 countries and territories that had used OPV in 2015 had successfully withdrawn OPV2 by ceasing use of tOPV in their national immunization programs. This article provides an overview of the global efforts and challenges in successfully implementing this unprecedented global initiative, including (1) coordination and tracking of key global planning milestones, (2) guidance facilitating development of country specific plans, (3) challenges for planning and implementing the switch at the global level, and (4) best practices and lessons learned in meeting aggressive switch timelines. Lessons from this monumental public health achievement by countries and partners will likely be drawn upon when bOPV is withdrawn after polio eradication but also could be relevant for other global health initiatives with similarly complex mandates and accelerated timelines.

To meet the demand for effective and affordable inactivated polio vaccines (IPVs), a reduced dose, aluminium hydroxide (Al(OH)3)-adjuvanted IPV vaccine was developed (IPV-Al, Picovax®) and evaluated in clinical trials. The present trial is an extension of two previous trials (a primary and a booster trial). The aim was to evaluate the persistence of seroprotective antibodies (poliovirus type-specific antibody titre ≥ 8) in 4-year-old children who previously received IPV–Al as primary and booster vaccine doses and to determine the potential booster response and safety profile of an additional dose of IPV-Al. Children participating in the two previous trials were invited to receive one additional dose of IPV-Al at 4 years of age (2.5 years after the booster dose) and to have their blood samples collected to measure the pre- and post-vaccination antibody titres. Systemic adverse events (AEs) and local reactogenicity were recorded. At study entry, the seroprotection rates were 89.2%, 100% and 91.1% against poliovirus type 1, 2 and 3, respectively. The additional vaccination with IPV-Al boosted the level of poliovirus type 1, 2 and 3 antibodies to above the seroprotection threshold for all but one subject, i.e., 99.4% for type 1 and 100% for types 2 and 3. The additional dose induced a robust booster response of a 26.3-, 13.9- and 30.9-fold increase in titre for poliovirus types 1, 2 and 3, respectively. The vaccine was well tolerated, with only mild and transient AEs reported. The present trial demonstrated that the primary vaccination with an aluminium-adjuvanted reduced dose IPV induced a persistent immune memory as evidenced by the robust anamnestic response when the subjects were re-exposed to the antigen 2.5 years after the last dose. Thus, the IPV-Al is an efficient and safe addition to increase the availability of inactivated polio vaccines globally. (ClinicalTrials.gov reg no. NCT04448132).

In May 1988 the World Health Assembly set to World Health Organization (WHO) the goal to achieve a global eradication of poliomyelitis by the year 2000. Surveillance of the acute flaccid paralysis (AFP) remains the ‘gold standard’ for the detection of polio. The criterion of sensitivity of the surveillance system is the incidence from non-polio related AFP, in children under 15 years of age. The aim is to detect more than 1 case of AFP, per 100,000 children. In 2019, WHO announced the eradication of wild poliovirus 3, and poliovirus 2 was eradicated in 2015. Wild poliovirus 1 continues to circulate. The main goals of the WHO Polio Eradication Strategy for the period 2022-2026 are: permanently interrupt all poliovirus transmission in endemic countries (Afghanistan and Pakistan), stop cVDPV (circulating vaccine-derived poliovirus) transmission and prevent outbreaks in non-endemic countries.