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Strengthening routine immunization is one of the four prongs of the Global Polio Eradication Initiative. Using data collected through 30-cluster sample household surveys of caretakers of children aged 12-23 months, this paper assessed the effectiveness of house-to-house visits on routine oral polio immunization completion, using simple frequency tables, bivariate and multivariate logistic regression analyses. Logistic regression results demonstrated that children in households where the caregivers reported receiving a household visit by health workers were more likely to be fully immunized for polio through routine immunization than other children, although results were significant only after correcting for confounders. In Ethiopia and India, children of caregivers who remembered a house-to-house visit were significantly and positively associated with routine polio vaccination completion (OR=2.2 and OR=2.2 respectively). In Angola, the association was positive, though not significant (OR=1.3). The evidence suggests that targeting high-risk areas for house-to-house visits played a role in increasing routine polio vaccination.

Though previous studies have suggested a non-specific beneficial effect of oral polio vaccine (OPV), there has been no evaluation of the mortality impact of national polio immunization days. On the other hand, studies examining the effect of OPV and diphtheria–tetanus–pertussis (DTP) vaccines, which are usually administered together in routine immunisation programmes in low-income countries, have found no beneficial or even a negative effect on infant survival. In 1998, we used the opportunity of two national immunisation days to examine the impact of OPV administered alone on survival for the 6103 children less than 5 years of age in the Bandim Health Project's study area in Guinea-Bissau. Survival was ascertained through regular surveillance from March 1998 until the beginning of the war on June 7, 1998, the end of 1998, or the end of 1999, respectively. The child register was linked with a register for the only paediatric ward in Bissau to determine the risk of hospitalisations. Among children under 5 years of age, 82% had received 1 or 2 doses of polio vaccines during the campaign. Though polio vaccination during the campaign was associated with slightly lower mortality, this difference was not significant for all children under 5 years of age (mortality ratio (MR) = 0.46 (0.18–1.15)). However, oral polio vaccination was associated with a beneficial effect for children under 6 months of age at the time of the campaign, the mortality ratio being 0.09 (95% CI 0.01–0.85) in the 3 months before the war controlling for significant background factors, including routine immunizations, antenatal consultations, and arm circumference. The polio-vaccinated children aged 0–5 months had fewer hospitalisations than children who had not been polio vaccinated (RR = 0.27 (0.10–0.76)). With longer follow-up to December 1998 or December 1999, the difference in mortality gradually disappeared, the MR for polio-vaccinated children being 0.61 (0.32–1.14) and 0.83 (0.51–1.34), respectively. Among children aged 6–59 months of age, measles vaccine was associated with a 56% reduction in mortality (MR = 0.44 (0.28–0.69)) and no effect of oral polio vaccine was measurable in this age group. The effect of polio vaccine among children less than 6 months of age could be due to selection bias but might also represent a non-specific beneficial immune stimulation and there is nothing to suggest that OPV might have a negative effect on infant survival. Studies of the possible non-specific effects of oral polio vaccine are warranted before OPV is withdrawn.

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.

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.

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.

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 Immunization Systems Management Group (IMG) was established to coordinate and oversee objective 2 of the Polio Eradication and Endgame Strategic Plan 2013–2018, namely, (1) introduction of ≥1 dose of inactivated poliovirus vaccine in all 126 countries using oral poliovirus vaccine (OPV) only as of 2012, (2) full withdrawal of OPV, starting with the withdrawal of its type 2 component, and (3) using polio assets to strengthen immunization systems in 10 priority countries. The IMG's inclusive, transparent, and partnership-focused approach proved an effective means of leveraging the comparative and complementary strengths of each IMG member agency. This article outlines 10 key factors behind the IMG's success, providing a potential set of guiding principles for the establishment and implementation of other interagency collaborations and initiatives beyond the polio sphere.

•Polio is considered a serious threat to public health in Pakistan.•Online commenters show empathy for polio health care workers.•Misinformation on polio vaccine as an amplification of new polio cases.•Online commenters correct misinformation and false claims by providing factual information on polio.•Pakistan launches the Perception Management Initiative (PMI) to block anti-vaccination propaganda social media pages. Polio, which is caused by poliovirus, is a contagious, potentially crippling, and deadly disease. Pakistan is one of the countries in which polio is still endemic in the 21st century. In 2019, 146 polio cases were reported across the country with some resulting in deaths. Following the spread of rumors insinuating that children were falling sick after receiving an anti-polio vaccine, a mob attacked and set fire to a small hospital in the Peshawar district in April 2019. The present study investigates readers’ discussions that emerged from Dawn’s online readers’ comments on polio-related news stories in Pakistan. Using thematic analysis, we analyzed (N = 2216) comments made by readers in the polio-related news stories published on Dawn.com from January 1, 2012, to March 1, 2020. Seven major themes emerged from the analysis of the comments: 1) reasons for and challenges resulting in the failure to eradicate polio; 2) proposed solutions and policy changes to eradicate polio; 3) misinformation; 4) criticism, frustration, and shame; 5) comparison of Pakistan to other countries; 6) the internet as a public sphere; 7) suffering, empathy, and appreciation. Overall, our findings suggested that commenters are knowledgeable about polio vaccines and consider polio a serious threat to public health in Pakistan. Our study not only validated previous study findings such as reasons, challenges, and issues related to polio vaccination, but also found new challenges in online news sites concerning misinformation on polio and polio vaccination in Pakistan.

To evaluate the immunogencity and safety for three immunization schedules of inactivated poliovirus vaccine (IPV) and bivalent oral poliovirus vaccine (bOPV) for providing a basis for further optimization of the polio sequential immunization schedule. To obtain immunogenicity data and to active surveillance the occurrence of adverse events following immunization (AEFI), healthy infants ≥ 2 months of age were randomly chosen in Hebei Province, and were divided into three groups to be vaccinated with IPV-bOPV-bOPV(Group a), IPV-IPV-bOPV(Group b) and IPV-IPV-IPV(Group c) at 2, 3 and 4 months of age respectively. AEFI cases related to poliomyelitis vaccines in Hebei province by passive surveillance from January 1, 2018 to December 31, 2022 were obtained from national adverse event following immunization surveillance system (NAEFISS). After basic immunization with polio vaccine, the positive conversion rate of neutralizing antibodies of types I, II and III were all > 97.00% and the positive rates were all > 98.00%, the geometric mean titer (GMT) was significantly higher than that before basic immunization, the GMT level of neutralizing poliovirus antibody after basic immunization was the highest in type I, followed by type III, and the lowest in type II. A total of 16 AEFI cases (2.52%) were reported by active surveillance, and 2903 AEFI cases (1.40%) were reported by passive surveillance. AEFI reported by both monitoring modalities were dominated by fever of common vaccine reactions. No rare serious adverse reactions like VAPP etc. were monitored and the overall regression was positive. All three immunization schedules for polio vaccine have demonstrated good immunogenicity and safety when administered to healthy populations.

•48.3% children are fully vaccinated in the super-high-risk union councils districts of Pakistan.•Vaccination coverage varies considerably across the super-high-risk union council districts.•Dropout rate between vaccine visits is as higher as 60.5% and as low as 4.9% in the districts.•Full immunization is associated with parental education level. The current polio epidemiology in Pakistan poses a unique challenge for global eradication as the country is affected by ongoing endemic poliovirus transmission. Across the country, 40 union councils (UCs) which serve as core reservoirs for poliovirus with continuous incidences of polio cases are categorized as super-high-risk union councils (SHRUCs). A cross-sectional survey was conducted in 39 SHRUCs using a two-stage stratified cluster sampling technique. 6,976 children aged 12–23 months were covered. A structured questionnaire was used for data collection. Data were analyzed using STATA version 17. Based on both vaccination records and recall, 48.3% of children were fully-, 35.4 % were partially-, and 16.3% were non-vaccinated in the SHRUC districts. A child is considered fully vaccinated when h/she completed vaccination for BCG, OPV0, OPV 1-3, Penta 1-3, PCV 1-3, IPV, and MCV1. Vaccination cards were seen for over half of the children in the SHRUC districts of Khyber Pakhtunkhwa (KP) and the majority of the SHRUC districts in Sindh, except for the SHRUC district of Malir the districts of Balochistan. Results for polio vacancies show that 60.9% of children from the SHRUC districts were vaccinated with at least three doses of OPV and one dose of IPV, while 20.4% were vaccinated with any OPV doses or IPV and 18.7% of children did not receive any polio vaccines. The dropout rate between vaccine visits was higher than the WHO-recommended cutoff point of 10% for all vaccine doses in the SHRUC districts. The likelihood of being fully vaccinated was higher among the children of educated parents. Full vaccination was found significant among the children of any SHRUC districts compared to district Killa Abdullah. Context-specific strategies with more focus on community engagement and targeted mobilization, along with robust monitoring mechanisms, would help address the underlying challenges of under-immunization in the SHRUCs.