Reversion of neurovirulent mutations, recombination and high intra-host diversity in vaccine-derived poliovirus excreted by patients with primary immune deficiency.

Patients with Primary immunodeficiency (PIDs) may be infected by Polioviruses (PVs), especially when vaccinated with live Oral Polio Vaccine before diagnosis. They may establish long-term shedding of divergent strains and may act as reservoirs of PV transmission. This study delved into the effect of the genetic evolution of complete PV genomes, from MHC class II-deficient patients, on the excretion duration and clinical outcomes. Stool samples from three PID patients underwent analysis for PV detection through inoculation on cell culture and real-time PCR, followed by VP1 partial sequencing and full genome sequencing using the Illumina technology. Our findings revealed a low number of mutations for one patient who cleared the virus, while two exhibited a high intra-host diversity favoring the establishment of severe outcomes. Neurovirulence-reverse mutations were detected in two patients, possibly leading to paralysis development. Furthermore, a recombination event, between type 3 Vaccine-Derived Poliovirus and Sabin-like1 (VDPV3/SL1), occurred in one patient. Our findings have suggested an association between intra-host diversity, recombination, prolonged excretion of the virus, and emergence of highly pathogenic strains. Further studies on intra-host diversity are crucial for a better understanding of the virus evolution as well as for the success of the Global Polio Eradication Initiative.

Monitoring the VDPV2 outbreak in Egypt during 2020-2021 highlights the crucial role of environmental surveillance and boosting immunization in combating Poliovirus.

BACKGROUND: Poliovirus is a highly infectious enterovirus (EV) that primarily affects children and can lead to lifelong paralysis or even death. Vaccine-derived polioviruses (VDPVs) are a great threat since they are derived from the attenuated virus in the Oral Poliovirus Vaccine (OPV) and can mutate to a more virulent form. The purpose of this study was to identify VDPV serotype 2 through the year 2020-2021 via surveillance of sewage samples collected from different localities and governorates in Egypt and stool specimens from Acute Flaccid Paralysis (AFP) cases. Both were collected through the national poliovirus surveillance system and according to the guidelines recommended by the WHO. METHODS: A total of 1266 sewage samples and 3241 stool samples from January 2020 to December 2021 were investigated in the lab according to World Health Organization (WHO) protocol for the presence of Polioviruses by cell culture, molecular identification of positive isolates on L20B cell line was carried out using real-time polymerase chain reactions (RT-PCR). Any positive isolates for Poliovirus type 2 and isolates suspected of Vaccine Derived Poliovirus Type 1 and type 3 screened by (VDPV1) or Vaccine Poliovirus Type 3 (VDPV3) assay in RT-PCR were referred for VP1 genetic sequencing. RESULTS: The outbreak was caused by circulating VDPV2 (cVDPV2) strains started in January 2021. By the end of February 2021, a total of 11 cVDPV2s were detected in sewage samples from six governorates confirming the outbreak situation. One additional cVDPV2 was detected later in the sewage sample from Qena (June 2021). The first and only re-emergence of VDPV2 in stool samples during the outbreak was in contact with Luxor in June 2021. By November 2021, a total of 80 VDPVs were detected. The Egyptian Ministry of Health and Population (MOHP), in collaboration with the WHO, responded quickly by launching two massive vaccination campaigns targeting children under the age of five. Additionally, surveillance systems were strengthened to detect new cases and prevent further spread of the virus. CONCLUSION: The continued threat of poliovirus and VDPVs requires ongoing efforts to prevent their emergence and spread. Strategies such as improving immunization coverage, using genetically stable vaccines, and establishing surveillance systems are critical to achieving global eradication of poliovirus and efficient monitoring of VDPVs outbreaks.

Qualitative real-time RT-PCR assay for nOPV2 poliovirus detection.

Based on the success of the Sabin2-based vaccine, a next-generation nOPV2 poliovirus vaccine has been developed. For epidemic monitoring and conducting epidemiological investigations, it is necessary to have a diagnostic assay with the ability to differentiate this variant from others. Here we describe such a real-time RT-PCR assay. The region with the cre insertion in the 5'-UTR was chosen as the target, and the limit of detection was 103 copies/mL (2.5×103 copies/mL using Probit analysis) determined using armored RNA particles. Sensitivity and specificity were 86.28 - 100 % and 76.84 - 100 %, respectively (with 95 % CI). Thus, this method can be effectively used when it is necessary to make a differential diagnosis of poliovirus strains.

Environmental Surveillance of Poliovirus and Non-polio Enteroviruses in Iran, 2017-2023: First Report of Imported Wild Poliovirus Type 1 Since 2000.

In Iran, which is at high risk of the Wild Poliovirus (WPV) and Vaccine-Derived Poliovirus (VDPV) importation due to its neighborhood with two polio endemic countries, Pakistan and Afghanistan, Environmental Surveillance (ES) was established in November 2017. Sistan-Balouchestan province was chosen for the ES due to its vicinity with Pakistan and Afghanistan. Five sewage collection sites in 4 cities (Zahedan, Zabol, Chabahar and Konarak) were selected in the high-risk areas. Since the establishment of ES in November 2017 till the end of 2023, 364 sewage specimens were collected and analyzed. The ES detected polioviruses which have the highest significance for polio eradication program, that is, Wild Poliovirus type 1 (WPV1) and Poliovirus type 2 (PV2). In April and May 2019, three of 364 (0.8%) sewage specimens from Konarak were positive for imported WPV1. According to phylogenetic analysis, they were highly related to WPV1 circulating in Karachi (Sindh province) in Pakistan. PV2 was also detected in 5.7% (21/364) of the sewage specimens, most of which proved to be imported from the neighboring countries. Of 21 isolated PV2s, 7 were VDPV2, of which 5 proved to be imported from the neighboring countries as there was VDPV2 circulating in Pakistan at the time of sampling, and 2 were ambiguous VDPVs (aVDPV) with unknown source. According to the findings of this study, as long as WPV1 and VDPV2 outbreaks are detected in Iran's neighboring countries, there is a definite need for continuation and expansion of the environmental surveillance.

Genetic stabilization of attenuated oral vaccines against poliovirus types 1 and 3.

Vaccination with Sabin, a live attenuated oral polio vaccine (OPV), results in robust intestinal and humoral immunity and has been key to controlling poliomyelitis. As with any RNA virus, OPV evolves rapidly to lose attenuating determinants critical to the reacquisition of virulence1-3 resulting in vaccine-derived, virulent poliovirus variants. Circulation of these variants within underimmunized populations leads to further evolution of circulating, vaccine-derived poliovirus with higher transmission capacity, representing a significant risk of polio re-emergence. A new type 2 OPV (nOPV2), with promising clinical data on genetic stability and immunogenicity, recently received authorization from the World Health Organization for use in response to circulating, vaccine-derived poliovirus outbreaks. Here we report the development of two additional live attenuated vaccine candidates against type 1 and 3 polioviruses. The candidates were generated by replacing the capsid coding region of nOPV2 with that from Sabin 1 or 3. These chimeric viruses show growth phenotypes similar to nOPV2 and immunogenicity comparable to their parental Sabin strains, but are more attenuated. Our experiments in mice and deep sequencing analysis confirmed that the candidates remain attenuated and preserve all the documented nOPV2 characteristics concerning genetic stability following accelerated virus evolution. Importantly, these vaccine candidates are highly immunogenic in mice as monovalent and multivalent formulations and may contribute to poliovirus eradication.

Update on Vaccine-Derived Poliovirus Outbreaks - Worldwide, January 2020-June 2021.

As of May 1, 2016, use of oral poliovirus vaccine (OPV) type 2 for routine and supplementary immunization activities ceased after a synchronized global switch from trivalent OPV (tOPV; containing Sabin strain types 1, 2, and 3) to bivalent OPV (bOPV; containing Sabin strain types 1 and 3) subsequent to the certified eradication of wild type poliovirus (WPV) type 2 in 2015 (1-3). Circulating vaccine-derived poliovirus (cVDPV) outbreaks* occur when transmission of Sabin strain poliovirus is prolonged in underimmunized populations, allowing viral genetic reversion to neurovirulence, resulting in cases of paralytic polio (1-3). Since the switch, monovalent OPV type 2 (mOPV2, containing Sabin strain type 2) has been used for response to cVDPV type 2 (cVDPV2) outbreaks; tOPV is used if cVDPV2 co-circulates with WPV type 1, and bOPV is used for cVDPV type 1 (cVDPV1) or type 3 (cVDPV3) outbreaks (1-4). In November 2020, the World Health Organization (WHO) Emergency Use Listing procedure authorized limited use of type 2 novel OPV (nOPV2), a vaccine modified to be more genetically stable than the Sabin strain, for cVDPV2 outbreak response (3,5). In October 2021, the Strategic Advisory Group of Experts on Immunization (WHO's principal advisory group) permitted wider use of nOPV2; however, current nOPV2 supply is limited (6). This report updates that of July 2019-February 2020 to describe global cVDPV outbreaks during January 2020-June 2021 (as of November 9, 2021)† (3). During this period, there were 44 cVDPV outbreaks of the three serotypes affecting 37 countries. The number of cVDPV2 cases increased from 366 in 2019 to 1,078 in 2020 (7). A goal of the Global Polio Eradication Initiative's (GPEI) 2022-2026 Strategic Plan is to better address the challenges to early CVDPV2 outbreak detection and initiate prompt and high coverage outbreak responses with available type 2 OPV to interrupt transmission by the end of 2023 (8).

The Molecular Evolution of Type 2 Vaccine-Derived Polioviruses in Individuals with Primary Immunodeficiency Diseases.

The oral poliovirus vaccine (OPV), which prevents person-to-person transmission of poliovirus by inducing robust intestinal immunity, has been a crucial tool for global polio eradication. However, polio outbreaks, mainly caused by type 2 circulating vaccine-derived poliovirus (cVDPV2), are increasing worldwide. Meanwhile, immunodeficiency-associated vaccine-derived poliovirus (iVDPV) is considered another risk factor during the final stage of global polio eradication. Patients with primary immunodeficiency diseases are associated with higher risks for long-term iVDPV infections. Although a limited number of chronic iVDPV excretors were reported, the recent identification of a chronic type 2 iVDPV (iVDPV2) excretor in the Philippines highlights the potential risk of inapparent iVDPV infection for expanding cVDPV outbreaks. Further research on the genetic characterizations and molecular evolution of iVDPV2, based on comprehensive iVDPV surveillance, will be critical for elucidating the remaining risk of iVDPV2 during the post-OPV era.

Environmental Surveillance for Polioviruses in Haïti (2017-2019): The Dynamic Process for the Establishment and Monitoring of Sampling Sites.

Haïti is at risk for wild poliovirus (WPV) importation and circulation, as well as vaccine-derived poliovirus (VDPV) emergence. Environmental surveillance (ES) for polioviruses was established in Port au Prince and Gonaïves in 2016. During 2017-2019, initial ES sites were re-evaluated, and ES was expanded into Cap Haïtien and Saint Marc. Wastewater samples and data on weather, hour of collection, and sample temperature and pH were collected every 4 weeks during March 2017-December 2019 (272 sampling events) from 21 sites in Cap Haïtien, Gonaïves, Port au Prince, and Saint Marc. Samples were processed for the detection of polio and non-polio enteroviruses using the two-phase and "Concentration and Filter Elution" methodologies. Polioviruses were serotyped and underwent intra-typic characterization. No WPV or VDPVs were isolated. Sabin-like polioviruses (oral vaccine strain) of serotypes 1 and 3 were sporadically detected. Five of six (83%), one of six (17%), five of six (83%), and two of three (67%) sites evaluated in Cap Haïtien, Gonaïves, Port au Prince, and Saint Marc, respectively, had enterovirus isolation from >50% of sampling events; these results and considerations, such as watershed population size and overlap, influence of sea water, and excessive particulates in samples, were factors in site retention or termination. The evaluation of 21 ES sampling sites in four Haïtian cities led to the termination of 11 sites. Every-four-weekly sampling continues at the remaining 10 sites across the four cities as a core Global Polio Eradication Initiative activity.

Molecular epidemiology of enteroviruses and predominance of echovirus 30 in an Iranian population with aseptic meningitis.

Human enteroviruses are the most prevalent causes of aseptic meningitis worldwide. However, despite such predominancy, defining the enteroviral etiology of aseptic meningitis remains a diagnostic dilemma for the clinician in Iran. Therefore, this study was conducted to characterize the prevalence and clinical significance of enteroviral aseptic meningitis as well as the predominant enterovirus serotypes among patients with aseptic meningitis in the South of Iran.Cerebrospinal fluid (CSF) specimens were obtained from 73 patients with aseptic meningitis (52.1% males and 47.9% females), ages ranging from 1 month to 88 years. Following the extraction of nucleic acid, the detection of enteroviruses was performed by RT-PCR, targeting the 5' untranslated region of the genome, and sequencing. Enteroviruses were found in 46.6% of samples (34/73). The most predominant serotype was echovirus 30, followed by coxsackievirus B5 and poliovirus type 1 Sabin strain. The enterovirus infections were more prevalent among female patients (58.8%) and those below 5 years of age (52.9%). Although enterovirus infections were observed throughout the year, the infections were more prevalent during autumn with fever as the predominant clinical symptom. The outcomes revealed that enteroviruses are significant causes of aseptic meningitis in the South of Iran, while suspected cases of aseptic meningitis are usually monitored by bacterial culture and biochemical testing of CSF samples. Therefore, the etiology remains unknown in most cases. Molecular detection of viral pathogens should be included as a common approach in the screening of patients with aseptic meningitis to prevent unnecessary treatment and to improve clinical management.

Poliomyelitis seroprevalence in high risk populations of India before the trivalent-bivalent oral poliovirus vaccine switch in 2016.

INTRODUCTION: This study assessed the seroprevalence against all three polioviruses among the last cohort of infants aged 6-11 months who received tOPV before the tOPV-bOPV switch and had an opportunity to receive a full dose of inactivated poliovirus vaccine introduced in the routine immunization schedule. METHODS: Serum was tested for neutralizing antibodies against polioviruses among infants residing in three different risk- category states for poliovirus transmission in India viz., Bihar historically high-risk state for polio, Madhya Pradesh a State with low routine immunization coverage and Chhattisgarh with lower acute flaccid paralysis surveillance indicators. RESULTS: A total of 1113 serum samples were tested across the three states. The overall seroprevalence was 98.5% (97.7-99.2), 98.9% (98.3-99.5) and 94.4% (93.0-95.8) for poliovirus types 1, 2 and 3 respectively. The median antibody titers for corresponding serotypes were 575, 362 and 181. Infants who received five doses of tOPV showed respective seroprevalence rates of 98.7%, 98.7% and 93.7% against types 1, 2 and 3 polioviruses. There was no significant difference in seroprevalence across the group of IPV recipients. The median reciprocal titers across the groups of IPV recipient was significantly higher (p = 0.006) for poliovirus-3. CONCLUSION: The seroprevalence rates observed in the study are historically the highest in the series of serosurveys that India has conducted to assess the population immunity against polioviruses. Poliovirus 2 seroprevalence was very high at the time of the tOPV-bOPV switch in India effected in April 2016.

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 893 EV 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 × 10-3 s/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.

Decontamination efficacy of sodium hypochlorite solutions for poliovirus.

Effective decontamination procedures are critical to the successful manufacture and control of poliovirus vaccines to minimize the risk to personnel and the environment. Polio viruses have been reported to be more resistant to disinfectants than many other viruses. We assessed the efficacy of sodium hypochlorite-containing disinfectants for decontamination for three poliovirus serotypes to implement decontamination procedures that are fully compliant with the WHO GAP III and Health authorities' requirements. A 10.4 log reduction was observed with a 0.63% sodium hypochlorite solution in a suspension with high protein and high poliovirus concentrations diluted 10-fold compared with a 6 log reduction in an undiluted sample. Treatment efficacy increased with sodium hypochlorite content and decreased with sample protein content. The surface tests showed that two 1-min treatments, 5-min apart, with a 0.63% Chl sodium hypochlorite solution effectively reduced the concentration of all poliovirus serotypes by 10 log10, irrespective of the protein and virus concentration in the sample. Sodium hypochlorite solutions lower than 0.52% were less effective for complete inactivation of poliovirus. In conclusion, we demonstrated that a high level of virus reduction (>10 log10) can be achieved with sodium hypochlorite solutions with poliovirus in suspension and dried on surfaces.

Immunogenicity of three sequential schedules with Sabin inactivated poliovirus vaccine and bivalent oral poliovirus vaccine in Zhejiang, China: an open-label, randomised, controlled trial.

BACKGROUND: The globally synchronised introduction of inactivated poliovirus vaccine (IPV) and replacement of trivalent oral poliovirus vaccine (OPV) with bivalent OPV (bOPV) were successfully implemented in China's routine immunisation programme in May, 2016. In response to the global shortage of Salk-strain IPV, Sabin-strain IPV production was encouraged to develop and use in low-income and middle-income countries. We assessed the immunogenicity of the current routine poliovirus vaccination schedule in China and compared it with alternative schedules that use Sabin-strain IPV (sIPV) and bOPV. METHODS: This open-label, randomised, controlled trial recruited healthy infants aged 60-75 days from two centres in Zhejiang, China. Eligible infants were full-term, due for their first polio vaccination, weighed more than 2·5 kg at birth, were healthy on physical examination with no obvious medical conditions, and had no contraindications to vaccination. Infants were randomly assigned (1:1:1) using permuted block randomisation (block size of 12) to one of three polio vaccination schedules, with the first, second, and third doses given at ages 2 months, 3 months, and 4 months, respectively: sIPV-bOPV-bOPV (1sIPV+2bOPV group; current regimen), sIPV-sIPV-bOPV (2sIPV+1bOPV group), or sIPV-sIPV-sIPV (3sIPV group). The primary endpoint was the proportion of infants with seroconversion to each of the three poliovirus serotypes 1 month after the third dose. Serious and medically important adverse events were monitored for up to 30 days after each vaccination. We assessed immunity in the per-protocol population (all children who completed all three vaccinations and had pre-vaccination and post-vaccination laboratory data) and safety in all children who received at least one dose of study vaccine. This trial is registered with Clinicaltrials.gov, NCT03147560. RESULTS: Between May 1, 2016, and Dec 1, 2017, we enrolled and randomly assigned 528 eligible infants to one of the three treatment groups (176 in each group); 473 infants (158 in the 1sIPV+2bOPV group, 152 in the 2sIPV+1bOPV group, and 163 in the 3sIPV group) were included in the per-protocol population. 100% seroconversion against poliovirus types 1 and 3 was observed in all three groups. Infants who received an immunisation schedule containing bOPV had significantly higher antibody titres against poliovirus types 1 and 3 than did the sIPV-only group (2048 in all three treatment groups; p<0·0001). Seroconversion against type 2 poliovirus was observed in 98 (62%) infants in the 1sIPV+2bOPV group, 145 (95%) infants in the 2sIPV+1bOPV group, and 161 (99%) infants in the 3sIPV group. No serious adverse events occurred during the study; 14 minor, transient adverse events were observed, with no significant differences across study groups. INTERPRETATION: All three study schedules were well tolerated and highly immunogenic against poliovirus types 1 and 3. Schedules containing two or three sIPV doses had higher seroconversion rates against poliovirus type 2 than did the schedule with a single dose of sIPV. Our findings support inclusion of two sIPV doses in the routine poliovirus vaccination schedule in China to provide better protection against poliovirus type 2 than provided by the current regimen. FUNDING: Chinese Center for Disease Control and Prevention and China National Biotec Group Company.

Update on Vaccine-Derived Poliovirus Outbreaks - Worldwide, July 2019-February 2020.

Circulating vaccine-derived polioviruses (cVDPVs) can emerge in areas with low poliovirus immunity and cause outbreaks* of paralytic polio (1-5). Among the three types of wild poliovirus, type 2 was declared eradicated in 2015 (1,2). The use of trivalent oral poliovirus vaccine (tOPV; types 1, 2, and 3 Sabin strains) ceased in April 2016 via a 1-month-long, global synchronized switch to bivalent OPV (bOPV; types 1 and 3 Sabin strains) in immunization activities (1-4). Monovalent type 2 OPV (mOPV2; type 2 Sabin strain) is available for cVDPV type 2 (cVDPV2) outbreak response immunization (1-5). The number and geographic breadth of post-switch cVDPV2 outbreaks have exceeded forecasts that trended toward zero outbreaks 4 years after the switch and assumed rapid and effective control of any that occurred (4). New cVDPV2 outbreaks have been seeded by mOPV2 use, by both suboptimal mOPV2 coverage within response zones and recently mOPV2-vaccinated children or contacts traveling outside of response zones, where children born after the global switch are fully susceptible to poliovirus type 2 transmission (2-4). In addition, new emergences can develop by inadvertent exposure to Sabin OPV2-containing vaccine (i.e., residual response mOPV2 or tOPV) (4). This report updates the January 2018-June 2019 report with information on global cVDPV outbreaks during July 2019-February 2020 (as of March 25, 2020)† (2). Among 33 cVDPV outbreaks reported during July 2019-February 2020, 31 (94%) were cVDPV2; 18 (58%) of these followed new emergences. In mid-2020, the Global Polio Eradication Initiative (GPEI) plans to introduce a genetically stabilized, novel OPV type 2 (nOPV2) that has a lower risk for generating VDPV2 than does Sabin mOPV2; if nOPV2 is successful in limiting new VDPV2 emergences, GPEI foresees the replacement of Sabin mOPV2 with nOPV2 for cVDPV2 outbreak responses during 2021 (2,4,6).

Phylogenetic characteristics and molecular epidemiological analysis of novel enterovirus EV-B83 isolated from Tibet, China.

Enterovirus B83 (EV-B83) is a new member of the enterovirus B group. Currently, there are only two full-length genomic sequences of EV-B83 in the GenBank database and few VP1 region sequences. The aetiology and epidemiology of EV-B83 is unclear. 24 stool specimens were collected from twelve AFP patients and 298 stool specimens were collected from 298 healthy children in support of polio eradication activities in Tibet in 1999. Two polioviruses (isolated by L20B cell) and one non-polio enterovirus (isolated by RD cell) were isolated from AFP patients and nine polioviruses (isolated by L20B cell) and 90 non-polio enteroviruses (isolated by RD cell) were isolated from health children. Through molecular typing, we confirmed that the six of non-polio enteroviruses belong to EV-B83. The sequence similarity between the VP1 region of the Tibet isolates and that of the EV-B83 prototype strain was 80%. The maximum-likelihood phylogenetic tree of the partial VP1 region in EV-B83 demonstrated that EV-B83 formed four genotypes globally during the evolution process. The six Tibet EV-B83 strains formed the D genotype alone. Recombination analysis of Tibet EV-B83 showed that CV-B4, CV-A9, EV-B80, and EV-B106 may act as recombinant donors in multiple regions. The serum neutralization test showed that the antibody-positive rate was 58.8% and GMT was 1:19.70, which was higher than the previously reported results of EV-B106 and EV-B80. Temperature sensitivity test results showed that the six Tibet EV-B83 strains were temperature-insensitive with stronger virulence and potential infectivity, which was consistent with the results of the serum neutralization test. This study enriched the genome-wide sequence, epidemiological characteristics, and provided basic data for the follow-up study of EV-B83.

Lower immunity to poliomyelitis viruses in Australian young adults not eligible for inactivated polio vaccine.

There are limited long-term data on seroprevalence of neutralising antibody (nAb) to the three poliovirus serotypes following the switch from oral polio vaccine (OPV) to inactivated polio vaccine (IPV). In Australia, combination vaccines containing IPV replaced OPV in late 2005. Using serum and plasma specimens collected during 2012 and 2013, we compared prevalence of nAb to poliovirus type 1 (PV1), type 2 (PV2) and type 3 (PV3) in birth cohorts with differing IPV and OPV eligibility from an Australian population-based sample. In the total sample of 1673 persons aged 12 months to 99 years, 85% had nAb against PV1, 83% PV2 and 67% PV3. In the cohort 12 to <18 years (eligible for 4 OPV doses, last dose 8-14 years prior), a significantly lower proportion had nAb than in the 7 to <12 year cohort (eligible for 3 OPV doses and an IPV booster, last dose 3-8 years prior) for all poliovirus types: [PV1: 87.1% vs. 95.9% (P = 0.01), PV2: 80.4% vs. 92.9% (P = 0.003) and PV3: 38.1% vs. 84.0% (P < 0.0001)]. These data suggest individual-level immunity may be better maintained when an OPV primary schedule is boosted by IPV, and support inclusion of an IPV booster in travel recommendations for young adults who previously received only OPV.

Vaccine-Associated Neurological Adverse Events: A Case Report and Literature Review.

Vaccination is an effective strategy to reduce the burden of preventable illness. However, many clinical reports revealed that various vaccinations may associate with neurological disorders, mainly including autoimmune disease, febrile seizure, and vaccine-associated paralytic poliomyelitis (VAPP). Although more and more reports revealed that part of the above post-vaccine neurological disorders is not directly related to vaccination, it may be merely a coincidence. However, these reports may increase the hesitancy on vaccination for the public population and influence the coverage of vaccination. In this report, we described a child with acute flaccid paralysis possibly caused by a poliovirus vaccine. To provide feasible ways to realize or reduce the risk of neurological adverse events caused by vaccines, we further provide a mini-review of the literature of vaccination associated with neurological adverse events. This revealed that oral poliomyelitis vaccine use exclusively and type 2 serotype poliomyelitis vaccine virus were the risk factors for VAPP. The combination vaccine was associated with an increased risk of ADEM and FS following immunization when compared with the administration of vaccines separately. Even though cases have been reported that vaccination may be a trigger of anti-NMDARe and GBS, there is no direct evidence to prove that vaccination increased the risk of GBS and anti-NMDARe.