Bivalent Oral Polio Vaccine Research Articles

Childhood vaccination trends during 2019 to 2022 in Tanzania and the impact of the COVID-19 pandemic

ABSTRACT The COVID-19 pandemic has significantly disrupted healthcare systems at all levels globally, notably affecting routine healthcare services, such as childhood vaccination. This study examined the impact of these disruptions on routine childhood vaccination programmes in Tanzania. We conducted a longitudinal study over four years in five Tanzanian regions: Mwanza, Dar es Salaam, Mtwara, Arusha, and Dodoma. This study analyzed the trends in the use of six essential vaccines: Bacille Calmette-Guérin (BCG), bivalent Oral Polio Vaccine (bOPV), Diphtheria Tetanus Pertussis, Hepatitis-B and Hib (DTP-HepB-Hib), measles-rubella (MR), Pneumococcal Conjugate Vaccine (PCV), and Rota vaccines. We evaluated annual and monthly vaccination trends using time-series and regression analyses. Predictive modeling was performed using an autoregressive integrated moving average (ARIMA) model. A total of 32,602,734 vaccination events were recorded across the regions from 2019 to 2022. Despite declining vaccination rates in 2020, there was a notable rebound in 2021, indicating the resilience of Tanzania’s immunization program. The analysis also highlighted regional differences in vaccination rates when standardized per 1000 people. Seasonal fluctuations were observed in monthly vaccination rates, with BCG showing the most stable trend. Predictive modeling of BCG indicated stable and increasing vaccination coverage by 2023. These findings underscore the robustness of Tanzania’s childhood immunization infrastructure in overcoming the challenges posed by the COVID-19 pandemic, as indicated by the strong recovery of vaccination rates post-2020. We provide valuable insights into the dynamics of vaccination during a global health crisis and highlight the importance of sustained immunization efforts to maintain public health.

Halting vaccine-derived poliovirus circulation: the novel type 2 oral vaccine might not be enough

Halting vaccine-derived poliovirus circulation: the novel type 2 oral vaccine might not be enough

Oral booster vaccine antigen-Expression of full-length native SARS-CoV-2 spike protein in lettuce chloroplasts.

Oral booster vaccine antigen-Expression of full-length native SARS-CoV-2 spike protein in lettuce chloroplasts.

Time temperature indicators made with sublimating azulene derivatives as the functional dye for use of fast reaction rate

Time temperature indicators (TTIs) based on a dye sublimation process have been developed for full time monitoring of heat sensitive vaccines with shorter shelf‐life during cold chain transportation and storage. The structure of TTI and the methods to make the TTI are introduced. TTI 1 and TTI 2 introduced in the article were made with methyl azulene‐1‐carboxylate and methyl 3‐methylazulene‐1‐carboxylate as the functional dyes, respectively. The kinetic parameters of TTI 1 and TTI 2 were studied. To achieve a change of 30 in ∆E*ab, it takes 9.1 h at 37°C, 39.7 h at 25°C, 5.61 days at 15°C and 23.3 days at 5°C for TTI 1 and 37.2 h at 37°C, 128.8 h at 25°C, 37.5 days at 15°C and 102.5 days at 5°C for TTI 2. The activation energies (Ea) are calculated to be 91.87 kJ mol−1 and 97.99 kJ mol−1 for TTI 1 and TTI 2, respectively. A field simulation study was conducted on TTI 2 associated with bivalent oral polio vaccine (bOPV), yielding excellent correlation between the reaction rate of TTI 2 and the titre change of bOPV.

Antivenoms, hepatitis B vaccine and oral polio vaccine can be considered for storage and handling outside the cold chain following the innovative ‘controlled temperature chain’ approach

Possible applicability of controlled temperature chain (CTC) for selected antisera and vaccines was evaluated. Bivalent oral polio vaccine (OPV), hepatitis B vaccine (HepB vaccine; monovalent and combined) and antisera (lyophilized and liquid scorpion-antivenom and liquid snake-antivenom) were tested. Samples were stored at accelerated (35 ± 5 °C) and freezing (−25 ± 5 °C) conditions for 24 h, one week and one month in addition to recommended storage condition (2–8 °C), except OPV samples that were tested at accelerated and refrigerated (2–8 °C) conditions compared to recommended storage conditions (−25 ± 5 °C). All samples were tested for potency. Protein content and composition were determined for antisera samples. All vaccine vial-monitors were evaluated. HepB vaccine was subjected to aluminum-content assay, shake test and microscopical examination. No significant change in antisera potency was detectable under accelerated condition for a week. OPV stored in refrigerator for a month and at accelerated condition for 48 h maintained acceptable potency. Monovalent and combined HepB vaccine maintained acceptable potency under accelerated condition for a month and a week, respectively. Freezing adversely affected HepB vaccine. In conclusion, reevaluation of storage conditions of tested products is urgently required; this can reduce storage costs and improves their availability. Other products should be tested for possible CTC applicability.

Polio eradication in a chronic conflict setting lessons from the Republic of South Sudan, 2010-2020.

Introductionin 1988 the World Health Assembly set an ambitious target to eradicate Wild Polio Virus (WPV) by 2000, following the successful eradication of the smallpox virus in 1980. South Sudan and the entire African region were certified WPV free on August 25, 2020. South Sudan has maintained its WPV free status since 2010, and this paper reviewed the country’s progress, outlined lessons learned, and describes the remaining challenges in polio eradication.Methodssecondary data analysis was conducted using the Ministry of Health and WHO polio surveillance datasets, routine immunisation coverage, polio campaign data, and surveys from 2010 to 2020. Relevant technical documents and reports on polio immunisation and surveillance were also reviewed. Data analysis was conducted using EPI Info 7 software.Resultsadministrative routine immunisation coverage for bivalent Oral Polio Vaccine (OPV) 3rd dose declined from 77% in 2010 to 56% in 2020. In contrast, the administrative and post-campaign evaluation coverage recorded for the nationwide supplemental polio campaigns since 2011 was consistently above 85%; however, campaigns declined in number from four in 2011 to zero in 2020. Overall, 76% of notified cases of Acute Flaccid Paralysis (AFP) received three or more doses of the oral polio vaccine. The Annualized Non-AFP rate ranged between 4.0 to 5.4 per 100,000 under 15 years populations, and stool adequacy ranged from 83% to 94%.ConclusionSouth Sudan’s polio-free status documentation was accepted by the ARCC in 2020, thereby enabling the African Region to be certified WPV free on August 25, 2020. However, there are concerns as the country continues to report low routine immunisation coverage and a reduction in the number of polio campaigns conducted each year. It is recommended that the country conduct high-quality nationwide supplemental polio campaigns yearly to achieve and maintain the required herd immunity. It invests in its routine immunisation program while ensuring optimal AFP surveillance performance indicators.

Poliomyelitis amidst the COVID-19 pandemic in Africa: Efforts, challenges and recommendations

Poliomyelitis is the leading infectious cause of acute flaccid paralysis among children under five years of age, caused by the Wild Poliovirus, with no medical cure other than prevention through vaccination. The advent of mass vaccination campaigns against polio disease worldwide has greatly decreased the number of global cases and limited the rate of transmission. However, the emergence of Vaccine-derived Poliovirus due to genetic reversions in the live attenuated oral polio vaccine has posed a significant impediment to global polio eradication efforts. Therefore, There is a need to modify the vaccination regimen by utilizing more doses of inactivated poliovirus vaccine or adopting the bivalent oral polio vaccine in order to eliminate the transmission of Vaccine-derived Poliovirus. In addition, collective efforts from governments, health policymakers, vaccination groups and health-related bodies are required to improve vaccine coverage and suppress the circulation of Vaccine-derived Poliovirus.

Real-Time Stability of Lyophilized Sabin Formulated Live Attenuated Bivalent Oral Polio Vaccine

Real-Time Stability of Lyophilized Sabin Formulated Live Attenuated Bivalent Oral Polio Vaccine

Using Population-Based Structures to Actively Monitor AEFIs during a Mass Immunization Campaign—A Case of Measles–Rubella and Polio Vaccines

Active vaccine pharmacovigilance complements the standard passive or spontaneous surveillance system, which suffers from low reporting rates. This study aimed at utilizing population-based structures to report and profile adverse events following immunization (AEFI) with the measles and rubella vaccine (MR), or MR in combination with the bivalent oral polio vaccine (bOPV 1&3) (MR & bOPV), during mass vaccination in Uganda. Caretakers of children at home (less than 5 years) and schoolgoing children were followed up on and encouraged to report any AEFIs on day one, 2–3 days, 10 days, and 14 days after vaccination at school by their teachers and at-home, community-based village health teams. Out of 9798 children followed up on, 382 (3.9%) reported at least one AEFI, and in total, 517 AEFIs were reported. For MR, high temperature (21%), general feeling of weakness (19.3%), and headache (13%) were the most reported AEFIs, though there were variations on the days when they were reported. For the combination dose of MR & bOPV, high temperature (44%), rash (17%), general feeling of weakness (13%), and diarrhoea (8%) were the most common adverse events following immunization reported by caretakers. All 382 children cleared the AEFIs within 2 days, with 343 (90%) children reporting mild or moderate AEFIs and only 39 (10%) reporting severe AEFIs. The reported AEFIs are known and are mentioned in the vaccine leaflets with similar severity classification. Rates of AEFIs differed with the number of days after receiving the immunization. Conclusion: Active surveillance for AEFIs provides additional important information to national vaccine regulatory bodies. It reassures the public that vaccines are safe and that their safety is being taken seriously in Uganda, which would improve vaccine acceptability and confidence in the health system. Piggybacking on existing structures such as village health team members (for children at home) and teachers (for schoolgoing children) facilitates reaching vaccine recipients and increases reporting rates. Therefore, studies using active reporting of AEFIs should be conducted at regular intervals to report the overall incidence of AEs and to monitor trends and changes.

Inferring Numbers of Wild Poliovirus Excretors Using Quantitative Environmental Surveillance.

Response to and monitoring of viral outbreaks can be efficiently focused when rapid, quantitative, kinetic information provides the location and the number of infected individuals. Environmental surveillance traditionally provides information on location of populations with contagious, infected individuals since infectious poliovirus is excreted whether infections are asymptomatic or symptomatic. Here, we describe development of rapid (1 week turnaround time, TAT), quantitative RT-PCR of poliovirus RNA extracted directly from concentrated environmental surveillance samples to infer the number of infected individuals excreting poliovirus. The quantitation method was validated using data from vaccination with bivalent oral polio vaccine (bOPV). The method was then applied to infer the weekly number of excreters in a large, sustained, asymptomatic outbreak of wild type 1 poliovirus in Israel (2013) in a population where >90% of the individuals received three doses of inactivated polio vaccine (IPV). Evidence-based intervention strategies were based on the short TAT for direct quantitative detection. Furthermore, a TAT shorter than the duration of poliovirus excretion allowed resampling of infected individuals. Finally, the method documented absence of infections after successful intervention of the asymptomatic outbreak. The methodologies described here can be applied to outbreaks of other excreted viruses such as severe acute respiratory syndrome coronavirus 2 (SARS-CoV-2), where there are (1) significant numbers of asymptomatic infections; (2) long incubation times during which infectious virus is excreted; and (3) limited resources, facilities, and manpower that restrict the number of individuals who can be tested and re-tested.

Discovery of Foci of Type-2 Poliovirus Derived from Oral Polio Vaccine in Central African Republic in 2019

RésuméObjectifEn 2019, la République centrafricaine a découvert des foyers de poliovirus de type 2 dérivé vaccinal circulant (PVDV2c). L'objectif de ce travail est de décrire l'état vaccinal des enfants paralysés par le PVDV2c et leurs contacts et d'évaluer la circulation de cette souche chez ces contacts.Patients et MéthodeIl s'agit d'une étude rétrospective et descriptive. La population d'étude est constituée des enfants atteints de paralysie flasque aiguë (PFA) et de leurs contacts. Nous avons inclus les enfants paralysés dont les résultats de séquençage ont montré la présence du PVDV2c.RésultatsAu total, 21 enfants paralysés par le PVDVc et 64 contacts ont été enrôlés dans cette étude. Quatorze enfants paralysés sur 21 (66%) avaient reçu au moins une dose de vaccin antipoliomyélitique oral (VPO) bivalent contre 36 sur 64 (57%) chez les contacts (différence non significative). Parmi les malades vaccinés, 7 avaient reçu moins de trois doses. Pour le vaccin polio injectable (VPI), la couverture vaccinale chez les malades comme pour les contacts était de 33%.La proportion des enfants ayant reçu à la fois des doses de VPO et de VPI était de 33% chez les malades et 25% chez les contacts. Les contacts porteurs de VDPV2 ont été vaccinés par le VPO et VPI, respectivement 55% et 27%. Le VDPV2 et le Sabin 2 ont également été trouvés dans les selles des contacts, respectivement 34% et 9%.ConclusionL'insuffisance de vaccination en VPO et VPI pendant plusieurs années a des conséquences graves par la survenue de virus dérivé du vaccin et responsable de paralysie à vie. Pour arrêter l'épidémie de VDPVc, il faut renforcer la couverture vaccinale par une campagne de masse couvrant tous les districts en même temps.

Polio Outbreak Investigation and Response in The Horn of Africa: 2013-2016.

BackgroundThere has been civil strife, spanning more than two decades in some countries and recurrent natural disasters in the Horn of Africa (HoA). This has consistently maintained these countries in chronic humanitarian conditions. More important however is the fact that these crises have also denied populations of these countries access to access to lifesaving health services. Children in the difficult terrains and security compromised areas are not given the required immunization services to build their immunity against infectious diseases like the poliovirus. This was the situation in 2013 when the large outbreaks of poliovirus occurred in the HoA. This article reviews the epidemiology, risk, and programme response to what is now famed as the 2013-204 poliovirus outbreaks in the HoA and highlights the challenges that the programme faced in interrupting poliovirus transmission here.MethodsA case of acute flaccid paralysis (AFP) was defined as a child <15 years of age with sudden onset of fever and paralysis. Polio cases were defined as AFP cases with stool specimens positive for WPV.ResultsBetween 2013 and 2016, when transmission was interrupted 20,266 polio viruses were in the Horn of Africa region. In response to the outbreak, several supplementary immunization activities were conducted with oral polio vaccine (OPV) The trivalent OPV was used initially, followed subsequently by bivalent OPV, and targeting various age groups, including children aged <5 years, children aged <10 years, and individuals of any age. Other response activities were undertaken to supplement the immunization in controlling the outbreak. Some of these activities included the use of various communication strategies to create awareness, sensitize and mobilize the populations against poliovirus transmission.ConclusionsThe outbreaks were attributed to the existence of clusters of unvaccinated children due to inaccessibility to them by the health system, caused by poor geographical terrain and conflicts. The key lesson therefore is that the existence of populations with low immunity to infections will necessary constitutes breeding grounds for disease outbreak and of course reservoirs to the vectors. Though brought under reasonable control, the outbreaks indicate that the threat of large polio outbreaks resulting from poliovirus importation will remain constant unless polio transmission is interrupted in the remaining polio-endemic countries of the world.

Efforts Towards Polio Eradication in Madagascar: 1997 to 2017.

BackgroundIn 1988, the World Health Assembly launched the Global Polio Eradication Initiative. WHO AFRO is close to achieve this goal with the last wild poliovirus detected in 2014 in Borno States in Nigeria. The certification of the WHO African Region requires that all the 47 member states meet the critical indicators for a polio free status. Madagascar started implementing polio eradication activities in 1996 and was declared polio free in June 2018 in Abuja. This study describes the progress achieved towards polio eradication activities in Madagascar from 1977-2017 and highlights the remaining challenges to be addressed.MethodsData were collected from the national routine immunization services, Country Acute Flaccid surveillance databases and national reports of SIAS and Mop Up campaign. Country complete polio and immunization related documentation provided detailed historical information’s.ResultsFrom 1997 to 2017, Madagascar reported one wild poliovirus (WPV) outbreak and four circulating Vaccine Derived Polio Virus (cVDPV) oubreaks with a total of 21 polioviruses (1 WPV and 21 cVDPV). The last WPV and cVDPV were notified in 1997 in Antananarivo and 2015 in Sakaraha health districts respectively. Madagascar met the main polio surveillance indicators over the last ten years and made significant progress following the last cVDPV2 outbreak in 2014 -2015. In addition, the country successfully implemented the switch from trivalent Oral Polio Vaccine (tOPV) to bivalent Oral Polio vaccine (bOPV) and containment activities. Environmental Surveillance established since 2015 did not reveal any poliovirus. The administrative coverage of the 3rd dose of oral polio vaccine (OPV3) varied across the years from 55% in 1991 to a maximum of 95% in 2007 before a progressive decrease to 86% in 2017. The percentage of AFP cases with more than 3 doses of oral polio vaccines increased from 56% in 2014 to 88% in 2017. A total of 19 supplementary immunization activities (SIA) were conducted in Madagascar from 1997 to 2017, among which 3 were subnational immunization days (sNID) and 16 were national immunization days (NIDs). Poor routine coverage contributed to the occurrence of cVDPC outbreaks in the country; addressing this should remain a key priority for the country to maintain the polio free status.From 2015 to June 2017, Madagascar achieved the required criteria leading to the acceptance of the country’s polio-free documentation in June 2018 by ARCC. However, continuous efforts will be needed to maintain a highly sensitive polio surveillance system with emphasis on security compromised areas. Finally strengthening the health system and governance at all levels will be necessary if these achievements are to be sustained.ConclusionsHigh national political commitment and support of the Global Polio Eradication Partnership were critical for Madagascar to achieve polio free status. Socio-political instability, weakness of the health system, sub-optimal routine immunization performance, insufficient SIA quality and existing security compromised areas remain critical program challenges to address in order to maintaining the polio free status. Continuous high-level advocacy should be kept in order to ensure that new government authorities maintain polio eradication among the top priorities of the country.

Reduced mucosal immunity to poliovirus after cessation of trivalent oral polio vaccine

ABSTRACT The switch from using only trivalent oral polio vaccine (tOPV) to sequential schedules combining inactivated poliovirus vaccine (IPV) and bivalent oral polio vaccine (bOPV) for polio vaccination will cause changes to mucosal immunity against polio in infants, which plays an important role in preventing the poliovirus spread. Here, we analyzed mucosal immunity against poliovirus in the intestine during different sequential vaccination schedules. We conducted clinical trials in Guangxi Province, China on 1,200 2-month-old infants who were randomly assigned to one of three vaccination schedule groups: IPV-bOPV-bOPV, IPV-IPV-tOPV, and IPV-IPV-bOPV, with vaccine doses administered at 8, 12, and 16 weeks of age. Stool samples were collected from 10% of participants in each group before administration of the second vaccine doses and at 1, 2, and 4 weeks after the administrations of the second and third vaccine doses. Immunoglobulin A (IgA) in the stool samples was measured to analyze the mucosal immune response in the intestine. Because of the absence of poliovirus type 2 in bOPV, the vaccination schedule of IPV-IPV-bOPV did not sufficiently raise intestinal mucosal immunity against poliovirus type 2, although some cross-immunity was seen. The level of intestinal mucosal immunity was related to shedding status; shedders could produce intestinal mucosa IgA more quickly. The intestinal mucosal immunity level was not related to serum neutralizing antibody level. In the combined sequential vaccination schedule of IPV and bOPV, the risk of circulating vaccine-derived poliovirus type 2 (cVDPV2) may be increased owing to insufficient intestinal mucosal immunity against poliovirus type 2.

Advances in researches of serotype 2 novel oral polio vaccine

In April 2016, the Global Polio Eradication Initiative (GPEI) adjusted its polio vaccination strategy, converting trivalent oral polio vaccine (tOPV) into bivalent oral polio vaccine (bOPV), and withdrawing type 2 oral polio vaccine (OPV2) globally. However, after the withdrawal of OPV2, there were many outbreaks of type-2 circulating vaccine-derived poliovirus (cVDPV2) in Asia and Africa. In order to eradicate poliovirus completely, GPEI launched the research and development of the novel serotype 2 oral polio vaccine (nOPV2) in 2010 and considering whether it is necessary to reuse OPV. This paper summarizes the epidemiological situation of cVDPV2 before and after OPV2's withdrawal, the related factors affecting the reuse of OPV and the related research progress of nOPV2.

Polio Supplementary Immunization Activities During COVID-19 Pandemic: Experience from Penampang District, Sabah, Malaysia.

Background:Polio Supplementary Immunization Activities (SIAs) were carried out in the State of Sabah in response to the Vaccine Derived Poliovirus outbreak declared in December 2019. Prior to this, Malaysia had been polio-free over the past 27 years. This paper reported on the successful implementation of SIAs in the district of Penampang, Sabah, adapting (vaccine administration) to the COVID-19 pandemic.Methods:A series of meticulous planning, healthcare staff training, advocacy, and community engagement activities were conducted by the Penampang District Health Office. Bivalent Oral Polio Vaccine (bOPV) and monovalent Oral Polio Vaccine were administered over the period of 1 year via these methods: house to house, drive-through, static, and mobile posts. The targeted group was 22 096 children aged 13 years and below.Results:Polio SIAs in Penampang managed to achieve more than 90% coverage for both bOPV and mOPV. The overall vaccine wastage was reported to be 1.63%. No major adverse reaction was reported.Conclusion:High vaccine uptake during Polio SIAs in Penampang was attributed to good inter-agency collaboration, community engagement, intensified health promotion activities, and drive-through vaccination campaign.

Prevalence and Bayesian Phylogenetics of Enteroviruses Derived From Environmental Surveillance Around Polio Vaccine Switch Period in Shandong Province, China.

We present the results of environmental surveillance for poliovirus (PV) and non-poliovirus (NPEV) around the switch from trivalent to bivalent oral polio-vaccine (OPV) which occurred in China in May 2016. Sewage samples were collected in Jinan and Linyi city from 2015 to 2017. Enterovirus (EV) isolation, VP1 amplification, Sanger sequencing, and phylogenetic analyses were performed. Among105 sewage samples (36 in Jinan and 69 in Linyi), 101 were positive for EV, with 74.3% (78/105) PV-positive samples and 90.5% (95/105) NPEV-positive samples. A total of 893EV isolates were obtained, including 326 (36.5%) PVs and 567 (63.5%) NPEVs. Echovirus (E) -11 was the most common serotype out of 18 detected NPEV types (120/567), followed by E-3 (75/567) and E-6 (74/567). PV2 vanished and PV3 came to be the ascendant PV type in sewage after May 2016. Eight PV isolates were judged as pre-vaccine-derived poliovirus(pre-VDPV) and no VDPV or wild PV isolates were monitored. Bayesian phylogenetics demonstrated global E-11 originated in 1876 and evolved with the estimated rate of 4.63 × 10-3 nucleotide substitutions per site per year (s/s/y). Multiple circulating clusters that originated at different times were coexisting in Shandong province. The most recently common ancestor of global coxsackievirus B5 could date back to 1867, at the evolutionary rate of 3.95 × 10-3s/s/y. In conclusion, our study described the changes of PVs and NPEVs around the polio vaccine switch period and provided meaningful global molecular epidemiological data for further studies of EV-related diseases among the population.

Polio switch strategy: An obituary in the making?

India was certified free of polio in 2014. Until now, the oral polio vaccine (OPV) was being used in India. As the OPV is a live vaccine, vaccine-associated paralytic poliomyelitis may occur after its use. The aim is to replace the OPV with injectable polio vaccine. The Polio Eradication and Endgame Strategic Plan 2013–2018 has been made to eradicate polio. A switch from the trivalent OPV (tOPV) to bivalent OPV (bOPV) has been undertaken in all countries since April 2016. tOPV vials have been withdrawn and replaced by bOPV. In addition, the inactivated polio vaccine (IPV) has been introduced. The next step would be to remove the type 3 virus component followed by complete cessation of the OPV and a final switch to the IPV. The timeline has been fixed as 2018–2019. Replacement of a vaccine may raise fears in the community that need to be addressed. Re-emergence of circulating vaccine-derived poliovirus after withdrawal of the tOPV may occur. Proper disposal of vaccine vials needs to be ensured. Proper training of vaccinators is important. All stakeholders need to be incorporated, and focus should be more on deprived populations. The switch marks a significant step towards the final goal of polio eradication. Finally, the importance of community participation cannot be overemphasized. Sustained surveillance is the key to prevent occurrence of cases in polio-free countries through importation.

Immunogenicity and safety profile of a primary dose of bivalent oral polio vaccine given simultaneously with DTwP-Hb-Hib and inactivated poliovirus vaccine at the 4th visit in Indonesian infants

In this study, we aimed to evaluate the immunological protectivity of infants following four doses of bivalent oral polio vaccine (bOPV; Bio Farma), which were given simultaneously with DTwP-Hb-Hib (Pentabio®), along with one dose of inactivated poliovirus vaccine (IPV) at the fourth visit. A total of 143 newborn infants who fulfilled the inclusion criteria were enrolled and completed the study. Subjects received the first dose of bOPV at birth. On days 60, 90 and 120, bOPV was given simultaneously with Pentabio®. On day 120, one dose of IPV was also administered. Serum samples for serology analysis were collected before the first dose of bOPV (at day 0), before the second dose of bOPV (at day 60) and 30 days after the last dose of bOPV. In addition, the intensity, duration and relationship of each adverse event to the trial vaccines were assessed. Seroprotection rates after the fourth dose of bOPV were 100%, 91.6% and 99.3% for poliovirus P1, P2 and P3, respectively. Seroconversion rates after the fourth dose of bOPV were 100.0%, 93.3% and 100% for poliovirus P1, P2 and P3, respectively. There were no severe adverse events, and systemic reactions were generally mild during the 1–28 day post-vaccination period. Collectively, our findings indicate that bOPV given simultaneously with Pentabio® and one dose of IPV at the 4th visit was immunogenic and well tolerated.

Vaccine loss related to the expanded immunization program in Xinjiang Uygur Autonomous Region, 2016-2017

Objective: To assess the vaccine loss related to the Expanded Program on Immunization (EPI) in Xinjiang Uygur Autonomous Region so as to improve the management of vaccines. Methods: A total of 135 vaccination clinics were randomly selected, using a stratified cluster sampling method. In each clinic, data on vaccination was collected between 2016 and 2017, including the number of doses in routine immunization program and supplementary immunization activities (i.e., vaccine doses in vials that were opened for use) on polio vaccine, number of doses administered to children and the number of doses discarded (e.g., expired vaccine or broken vials that had not been opened for use), etc. Coefficient on vaccine loss was calculated with the following equation: vaccine loss coefficient=(number of vaccine doses used)/(number of vaccine doses administered). The vaccine discard rate appeared as: number of vaccine doses discarded)/number of vaccine doses used. Results: For vaccines in single-dose vials [diphtheria-tetanus-pertussis vaccine (DTaP) and trivalent oral polio virus vaccine (tOPV)], the loss coefficients appeared as 1.00 and 1.02, respectively. For vaccines in multi-dose vials [bivalent oral polio vaccine (bOPV), group A meningococcal polysaccharide vaccine (MPV-A), diphtheria-tetanus combined vaccine (DT) and bacilli Calmette-Guérin (BCG) vaccine], the loss coefficients were 1.58, 1.67, 1.68, and 3.02, respectively. The coefficients of EPI vaccine loss in urban, rural, and pastoral area vaccination clinics ranged between 1.00-2.84, 1.00-3.71, and 1.00-2.27, respectively. Loss coefficients ranged between 1.00-3.00, 1.00- 4.41, and 1.00-1.94, respectively, were seen in township clinics, village clinics, and decentralized vaccination clinics. Coefficients on larger vaccine loss were associated with longer intervals between clinic sessions and with fewer vaccinations administrations per day. Conclusions: In Xinjiang, coefficients on the loss of multi-dose EPI vaccines were high. The coefficients on loss were different from the levels of region and types of clinics, and time interval between clinic sessions. Programs on refining the management and distribution of EPI vaccines, to minimize the vaccine loss were recommended.