Safety and immunogenicity of inactivated poliovirus vaccine based on Sabin strains with and without aluminum hydroxide: A phase I trial in healthy adults

Development of an animal component free production process for Sabin inactivated polio vaccine

Inactivated polio vaccine production using attenuated Sabin strains (sIPV) instead of wild type polio viruses (cIPV) is an initiative encouraged by the World Health Organization. This use of attenuated viruses is preferred as it reduces risks related to potential outbreaks during IPV production. Previously, an sIPV production process was set up based on the cIPV production process. Optimizing this process while using only animal component free (ACF) substances allows reduction of operational costs and mitigates risks of adverse effects related with animal derived compounds. Here, development of a process for production of sIPV using only ACF compounds, is described.

The upstream process required a change in cell growth medium from serum-containing medium to ACF medium, while virus production media remained the same as the already used M199 medium was free of animal components. In the downstream process multiple modifications in existing unit operations were made including addition of a diafiltration step prior to inactivation. After optimizing each unit operation, robustness of the whole process was demonstrated using design of experiments (DoE) methodology. By using DoE we were able to vary different process parameters across unit operations to assess the impact on our quality attributes. The developed process was robust as the observed variation for quality attributes due to differences in process parameters remained within specification.

The resulting pilot process showed not only to be robust, but also to have a considerable higher product yield when compared to the serum containing sIPV process. Product yields are now comparable to the cIPV process based on using wild type polio viruses. Moreover, the potency of the produced vaccine was comparable that of cIPV vaccine. The developed ACF sIPV process can be transferred to vaccine manufacturers at the end-of pre-clinical development phase, at lab- or pilot scale, before production of clinical trial material.

Aluminium adjuvants versus placebo or no intervention in vaccine randomised clinical trials: a systematic review with meta-analysis and Trial Sequential Analysis

OBJECTIVES

To assess the benefits and harms of aluminium adjuvants versus placebo or no intervention in randomised clinical trials in relation to human vaccine development.

DESIGN

Systematic review with meta-analysis and trial sequential analysis assessing the certainty of evidence with Grading of Recommendations Assessment, Development and Evaluation (GRADE).

DATA SOURCES

We searched CENTRAL, MEDLINE, Embase, LILACS, BIOSIS, Science Citation Index Expanded and Conference Proceedings Citation Index-Science until 29 June 2021, and Chinese databases until September 2021.

ELIGIBILITY CRITERIA

Randomised clinical trials irrespective of type, status and language of publication, with trial participants of any sex, age, ethnicity, diagnosis, comorbidity and country of residence.

DATA EXTRACTION AND SYNTHESIS

Two independent reviewers extracted data and assessed risk of bias with Cochrane's RoB tool 1. Dichotomous data were analysed as risk ratios (RRs) and continuous data as mean differences. We explored both fixed-effect and random-effects models, with 95% CI. Heterogeneity was quantified with I² statistic. We GRADE assessed the certainty of the evidence.

RESULTS

We included 102 randomised clinical trials (26 457 participants). Aluminium adjuvants versus placebo or no intervention may have no effect on serious adverse events (RR 1.18, 95% CI 0.97 to 1.43; very low certainty) and on all-cause mortality (RR 1.02, 95% CI 0.74 to 1.41; very low certainty). No trial reported on quality of life. Aluminium adjuvants versus placebo or no intervention may increase adverse events (RR 1.13, 95% CI 1.07 to 1.20; very low certainty). We found no or little evidence of a difference between aluminium adjuvants versus placebo or no intervention when assessing serology with geometric mean titres or concentrations or participants' seroprotection.

CONCLUSIONS

Based on evidence at very low certainty, we were unable to identify benefits of aluminium adjuvants, which may be associated with adverse events considered non-serious.

Immunochemical and Biophysical Characterization of Inactivated Sabin Poliovirus Products: Insights into Rapid Quality Assessment Tools

The aim of this study was to demonstrate the strength of combining immunochemical and biophysical analysis tools for assessing the quality of Sabin inactivated poliovirus vaccine (Sabin-IPV) bulk products. We assessed Sabin-IPV serotypes 1, 2 and 3 from six different manufacturers and evaluated their comparability through biosensor analysis and biophysical characterization methods, including tryptophan fluorescence and asymmetrical flow field-flow fractionation - multi-angle light scattering analysis. These methods enabled us to assess antigenic as well as conformational and structural integrity profiles, respectively. Based on Sabin-IPV samples that were subjected to accelerated storage conditions, we revealed that existing immunochemical methods exhibit remarkably similar trends to the results obtained by the biophysical characterization methods. While the results underpin that the comparability of Sabin-IPV bulk products of different manufacturers is poor, information about their quality can rapidly be obtained by using both immunochemical and biophysical methods. Furthermore, the study highlights that quality assessment of Sabin-IPV can be obtained through biophysical techniques can complement the assessments performed with monoclonal antibodies and suggests that similar techniques could be employed to characterize other enteroviruses.

Comparison of the neutralizing activities of antibodies in clinical sera against both Sabin and wild-type polio pseudoviruses

The cost-effectiveness of the Sabin inactivated poliovirus vaccine derived from the Sabin strains (S-IPV) and its reduced biosecurity risks during its manufacture make it the vaccine of choice over the IPVs derived from wild-type polioviruses. However, it is difficult to evaluate whether S-IPVs can achieve wild-type poliovirus containment in China, making its development there less attractive. To facilitate the development and adoption of S-IPVs in China, the aim of this study was to develop an alternative neutralizing assay using either a polio pseudovirus derived from a Sabin strain (S-pNA) or one derived from a wild-type strain (w-pNA) to replace the conventional neutralizing assay which uses live polioviruses. A total of 100 sera were collected from children immunized with an oral poliovirus vaccine and their antibody titers were assessed by both the S-pNA and w-pNA. The results showed that this method was feasible for the quantification of neutralizing antibody activities in the sera of the vaccinated individuals. The Wilcoxon signed-rank sum test indicated that the neutralizing antibody titers obtained against the Sabin strains were higher than those obtained with the wild-type strains for types 1 and 3, while for type 2, the titers against the wild-type strains were higher than those against the Sabin strains (p < 0.001 for all three types). It is hoped that this assay could be used to assess whether immune sera by the S-IPV possess adequate neutralizing capacity against both attenuated and wild-type poliovirus strains.

Safety and immunogenicity of a new Sabin inactivated poliovirus vaccine candidate produced on the PER.C6® cell-line: a phase 1 randomized controlled trial in adults

This first-in-human study (NCT03032588), conducted in Belgium, evaluated a new inactivated poliovirus vaccines (IPV) candidate based on Sabin poliovirus strains grown on the high-yield PER.C6® cell line. Healthy adults (N = 32) were randomized (1:1) to receive a single dose of PER.C6-based Sabin-IPV (sIPV, 15:35:112.5 DU/dose) or conventional Salk-IPV (cIPV, 40:8:32 DU/dose). Reactogenicity was assessed up to 7 days after vaccination, immunogenicity 28 days after vaccination, and safety up to 6 months after vaccination.Solicited adverse events (AEs) were mild to moderate, no changes of concern in vital signs or safety laboratory values were observed, and no severe AEs (SAEs) or vaccine-related unsolicited AEs were reported after vaccination. A trend to more frequent solicited AEs after sIPV than after cIPV administration was observed. Most participants had preexisting neutralizing antibodies against poliovirus types (titer ≥8), which were strongly boosted by sIPV. Post-vaccination geometric mean titers were high (≥12,000) and similar across the two vaccination groups. Only participants with very high preexisting antibody levels did not show a vaccine-induced response, defined in seropositive participants as a 4-fold titer increase. The 10 initially seronegative (titer <8) participants (n = 5 in each study group) seroconverted and all participants had seroprotective antibody levels post-vaccination. The antibodies elicited by sIPV neutralized both Sabin and Salk poliovirus strains.In conclusion, the PER.C6®-based sIPV was well tolerated and highly immunogenic in adults with preexisting antibodies to poliovirus.

Safety and immunogenicity of a new inactivated polio vaccine made from Sabin strains: a randomized, double-blind, active-controlled, phase 2/3 seamless study

Background

A new inactivated polio vaccine made from Sabin strains (sIPV) was developed as part of the global polio eradication initiative.

Methods

This randomized, double-blind, active-controlled, phase 2/3 seamless study was conducted in 2 stages. Healthy infants aged 6 weeks were randomly assigned to receive 3 doses of 1 of 4 study vaccines at 6, 10, and 14 weeks of age (336 received low-, middle-, or high-dose sIPV, or conventional IPV [cIPV] in stage I, and 1086 received lot A, B, or C of the selected sIPV dose, or cIPV in stage II). The primary outcome was the seroconversion rate 4 weeks after the third vaccination.

Results

In stage I, low-dose sIPV was selected as the optimal dose. In stage II, consistency among the 3 manufacturing lots of sIPV was demonstrated. The seroconversion rates for Sabin and wild strains of the 3 serotypes after the 3-dose primary series were 95.8% to 99.2% in the lot-combined sIPV group and 94.8% to 100% in the cIPV group, proving the noninferiority of sIPV compared to cIPV. No notable safety risks associated with sIPV were observed.

Conclusions

Low-dose sIPV administered as a 3-dose vaccination was safe and immunogenic compared to cIPV.

Clinical Trials Registration

NCT03169725.

A phase Ⅱ, randomized, controlled trial to evaluate the safety and immunogenicity of a Sabin strain-based inactivated polio vaccine

This phase Ⅱ, randomized, controlled trial aimed to evaluate the safety and immunogenicity of a various Sabin IPV preparations. Six hundred infants aged 60 ~ 90 days received one of five different vaccines: low- (group A), medium- (group B) or high-D antigen content (group C) of an experimental Sabin IPV, control Sabin IPV (group D) or control Salk IPV (group E), on a 0-1-2 month schedule. Participants were observed and followed up within 30 days of each dose to assess safety. Serum samples were collected before the first dose and 30 days after the third dose to assess immunogenicity. After three doses, type-1 seroconversion rates of groups A-E were 99.1%, 100.0%, 99.1%, 99.0%, and 93.4%, respectively; type-2 seroconversion rates were 93.5%, 97.1%, 98.1%, 95.1%, and 91.5%, respectively; and type-3 seroconversion rates were 95.4%, 98.1%, 98.1%, 95.1%, and 100.0%, respectively. Only type-1 seroconversion rates differed significantly for group E. The incidences of injection-site redness (A: 21.9%, B: 23.7%, C: 29.4%, D: 16.2%, E: 12.7%), swelling (A: 6.7%, B: 6.8%, C: 5.0%, D: 0.0%, E: 1.7%) and pain (A: 5.0%, B: 6.8%, C: 7.6%, D: 0.0%, E: 0.9%) all were significantly higher for experimental vaccines relative to control groups. No SAEs were detected related to vaccination, and most adverse reactions were mild or moderate in severity. In conclusion, the experimental Sabin IPVs with low-, medium-, and high-D antigen content all revealed good safety and immunogenicity profiles although being more reactogenic than the control vaccines.

The effect of maternal poliovirus antibodies on the immune responses of infants to poliovirus vaccines

Background

Maternal poliovirus antibodies could provide passive immunity to the newborns from poliovirus infection during their first few months of life, but they may impair the immune responses of infants to the poliovirus vaccine as well. In our study, we pooled the data from three clinical trials of the inactivated poliovirus vaccine (IPV) based on Sabin strains to investigate the effect of maternal poliovirus antibodies on the immune responses of infants to poliovirus vaccines.

Methods

There were five groups in the pooled analysis, including low-dose Sabin IPV, medium-dose Sabin IPV, high-dose Sabin IPV, control Sabin IPV, and control Salk IPV groups. We reclassified the infants in different groups according to their maternal poliovirus antibodies by two methods, the first one included maternal antibody negative (< 1:8) and maternal antibody positive (≥1:8), and the second one included maternal antibody titer < 1:8, 1:8 ~ < 1:32 and ≥ 1:32. Then, we compared the geometric mean titers (GMTs), geometric mean antibody fold increases (GMIs) and seroconversion rates of poliovirus type-specific neutralizing antibodies after vaccination among participants with different maternal poliovirus antibody levels.

Results

The GMTs and GMIs of three types of poliovirus antibodies after vaccination in maternal antibody negative participants were significantly higher than those in maternal antibody positive participants. The seroconversion rates of type II and type III poliovirus antibodies in maternal antibody positive participants were significantly lower than those in maternal antibody negative participants. Among participants with maternal antibody titer < 1:8, 1:8 ~ < 1:32 and ≥ 1:32, the GMTs and GMIs of three types of poliovirus antibodies after vaccination showed a tendency to decline with the increasing of maternal antibody levels. The seroconversion rates of three types of poliovirus antibodies in participants with maternal antibody titer ≥1:32 were significantly lower than those in participants with maternal antibody titer < 1:8 and 1:8 ~ < 1:32.

Conclusions

Maternal poliovirus antibodies interfered with the immune responses of infants to poliovirus vaccines, and a high level of maternal antibodies exhibited a greater dampening effect.

Trial registration

ClinicalTrials.govNCT04264598 February 11, 2020; ClinicalTrials.govNCT04264546 February 11, 2020; ClinicalTrials.govNCT03902054 April 3, 2019. Retrospectively registered.

Safety and immunogenicity of experimental stand-alone trivalent, inactivated Sabin-strain polio vaccine formulations in healthy infants: A randomized, observer-blind, controlled phase 1/2 trial

BACKGROUND

To increase the global supply of affordable IPV vaccine, preferably using Sabin viruses to comply with GAPIII requirements, Takeda has assessed three dosages of a stand-alone sIPV.

METHODS

In this phase I/II study two cohorts of 40 adults and 60 toddlers, respectively, were initially assessed for safety after receiving high-dosage sIPV compared with placebo (adults) or Salk IPV (toddlers). A cohort of 240 infants was then enrolled and randomized (1:1:1:1) to receive low-, medium- or high-dosage sIPV, or a reference Salk IPV in a three-dose primary schedule at 6, 10 and 14 weeks of age. Parents completed safety diaries for 4 weeks after each dose, and immunogenicity was measured as neutralization antibody titers at baseline and four weeks after vaccination.

RESULTS

All vaccinations were generally well-tolerated and sIPV had a comparable safety profile to the control arm in adults or the reference Salk IPV vaccine in toddlers and infants. Infants displayed dosage-dependent immune responses to sIPV when assayed using Sabin strains, which were equivalent to the reference IPV in the high-dosage sIPV group for serotypes 1 and 2, but not for Sabin and Salk serotype 3. Seroconversion rates (SCR) of the low- and medium-dosage groups were significantly lower than the Salk IPV group for both Sabin and Salk serotypes 1 and type 2 (p < 0.05), with no significant differences for Salk or Sabin serotypes 3. Responses to sIPV, particularly to Sabin types 1 and 2, were higher in initially seronegative infants, indicating possible interference by maternally-derived antibodies.

CONCLUSIONS

A novel stand-alone Sabin-based IPV vaccine was well tolerated with an acceptable safety profile, but less immunogenic than reference Salk IPV at 6, 10 and 14 weeks of age for Salk serotypes 1 and 2, with apparent interference by maternal antibodies. Additional preclinical assessments will be made before any further clinical development.

Equivalent schedules of intradermal fractional dose versus intramuscular full dose of inactivated polio vaccine for prevention of poliomyelitis

BACKGROUND

Poliomyelitis is a debilitating and deadly infection. Despite exponential growth in medical science, there is still no cure for the disease, which is caused by three types of wild polioviruses: types 1, 2, and 3. According to the Global Polio Eradication Initiative (GPEI), wild poliovirus is still in circulation in three countries, and fresh cases have been reported even in the year 2018. Due to the administration of live vaccines, the risk for vaccine-derived poliovirus (VDPV) is high in areas that are free from wild polioviruses. This is evident based on the fact that VDPV caused 20 outbreaks between 2000 and 2011. Recent recommendations from the World Health Organization favoured the inclusion of inactivated poliovirus vaccine (IPV) in the global immunisation schedule. IPV can be delivered in two ways: intramuscularly and intradermally. IPV was previously administered intramuscularly, but shortages in vaccine supplies, coupled with the higher costs of the vaccines, led to the innovation of delivering a fractional dose (one-fifth) of IPV intradermally. However, there is uncertainty regarding the efficacy, immunogenicity, and safety of an intradermal, fractional dose of IPV compared to an intramuscular, full dose of IPV.

OBJECTIVES

To compare the immunogenicity and efficacy of an inactivated poliovirus vaccine (IPV) in equivalent immunisation schedules using fractional-dose IPV given via the intradermal route versus full-dose IPV given via the intramuscular route.

SEARCH METHODS

We searched CENTRAL, MEDLINE, Embase, 10 other databases, and two trial registers up to February 2019. We also searched the GPEI website and scanned the bibliographies of key studies and reviews in order to identify any additional published and unpublished trials in this area not captured by our electronic searches.

SELECTION CRITERIA

Randomised controlled trials (RCTs) and quasi-RCTs of healthy individuals of any age who are eligible for immunisation with IPV, comparing intradermal fractional-dose (one-fifth) IPV to intramuscular full-dose IPV.

DATA COLLECTION AND ANALYSIS

We used standard methodological procedures expected by Cochrane.

MAIN RESULTS

We included 13 RCTs involving a total of 7292 participants, both children (n = 6402) and adults (n = 890). Nine studies were conducted in middle-income countries, three studies in high-income countries, and only one study in a low-income country. Five studies did not report methods of randomisation, and one study failed to conceal the allocations. Eleven studies did not blind participants, and six studies did not blind outcome assessments. Two studies had high attrition rates, and one study selectively reported the results. Three studies were funded by pharmaceutical companies. Paralytic poliomyelitis. No study reported data on this outcome. Seroconversion rates. These were significantly higher for all three types of wild poliovirus for children given intramuscular full-dose IPV after a single primary dose and two primary doses, but only significantly higher for type two wild poliovirus given intramuscularly after three primary doses: • dose one (six studies): poliovirus type 1 (odds ratio (OR) 0.30, 95% confidence interval (CI) 0.22 to 0.41; 2570 children); poliovirus type 2 (OR 0.43, 95% CI 0.31 to 0.60; 2567 children); poliovirus type 3 (OR 0.19, 95% CI 0.12 to 0.30; 2571 children); • dose two (three studies): poliovirus type 1 (OR 0.23, 95% CI 0.16 to 0.33; 981 children); poliovirus type 2 (OR 0.41, 95% CI 0.28 to 0.60; 853 children); and poliovirus type 3 (OR 0.12, 95% CI 0.07 to 0.22; 855 children); and • dose three (three studies): poliovirus type 1 (OR 0.45, 95% CI 0.07 to 3.15; 973 children); poliovirus type 2 (OR 0.34, 95% CI 0.19 to 0.63; 973 children); and poliovirus type 3 (OR 0.18, 95% CI 0.01 to 2.58; 973 children). Using the GRADE approach, we rated the certainty of the evidence as low or very low for seroconversion rate (after a single, two, or three primary doses) for all three poliovirus types due to significant risk of bias, heterogeneity, and indirectness in applicability/generalisability. Geometric mean titres. No study reported mean antibody titres. Median antibody titres were higher for intramuscular full-dose IPV (7 studies with 4887 children); although these studies also reported a rise in antibody titres in the intradermal group, none reported the duration for which the titres remained high. Any vaccine-related adverse event. Five studies (2217 children) reported more adverse events, such as fever and redness, in the intradermal group, whilst two studies (1904 children) reported more adverse events in the intramuscular group.

AUTHORS' CONCLUSIONS

There is low- and very low-certainty evidence that intramuscular full-dose IPV may result in a slight increase in seroconversion rates for all three types of wild poliovirus, compared with intradermal fractional-dose IPV. We are uncertain whether intradermal fractional-dose (one-fifth) IPV has better protective effects and causes fewer adverse events in children than intramuscular full-dose IPV.

Universal ELISA for quantification of D-antigen in inactivated poliovirus vaccines

To address the biosafety and biosecurity concerns related to the manufacture of inactivated polio vaccine (IPV), several manufacturers started producing it from attenuated Sabin strains. Slight immunological differences between wild and attenuated strains create a challenge for testing IPV potency, which is defined as the content of protective D-antigen determined in an ELISA test. Some ELISA reagents selected for testing conventional IPV made from wild strains (cIPV) may not be suitable for testing Sabin IPV (sIPV). This paper describes an ELISA procedure using human monoclonal antibodies selected to capture equally well both wild and attenuated strains of poliovirus. A unique monoclonal antibody neutralizing all three serotypes of poliovirus was used as the detection antibody. The method was shown to detect only D-antigen of both conventional and Sabin IPV and to be strictly serotype-specific. The method is highly sensitive and robust and produces linear results in a wide range of concentrations. We have also found that reference standards used for measuring potency of cIPV and sIPV must be made from respective vaccines. This makes it impossible to cross-calibrate potency reagents made from heterologous vaccine and requires the establishment of a new unit to measure potency of sIPV that is different from conventional D-antigen unit.

Effect of maternal antibody on the infant immune response to inactivated poliovirus vaccines made from Sabin strains

This study aimed to evaluate the effect of maternally derived antibody on the immunogenicity of Sabin IPV. A total of 600 infants were randomized to receive one of the five different vaccines: the high- (group A), medium- (group B) or low-dose (group C) of investigational Sabin IPV, the control Salk IPV (group D) or the control Sabin IPV (group E), at 2, 3 and 4 months of age. The post-vaccination GMTs, GMIs and seroconversion rates of poliovirus type-specific neutralizing antibody were analyzed for different maternal antibody levels. The correlations between maternal antibody levels and post-vaccination antibody responses were also modeled by linear regressions. The post-vaccination GMTs were significantly lower among infants with high maternal antibody titers for poliovirus type 1 or 2 mainly in the groups B, C, D and E. The GMIs and seroconversion rates decreased significantly with the increase of maternal antibody levels in all the five groups. In the groups A, B and C, maternal antibody levels were negatively associated with the post-vaccination antibody titers (for poliovirus type 1 and 2) and the fold increases of post-vaccination antibody (for all the 3 poliovirus types). With the reduce of potency of the investigational Sabin IPVs, the linear regression coefficients increased accordingly in the groups A, B and C. In conclusion, high levels of maternal poliovirus antibody could attenuate the immune responses to the Sabin IPVs. Altering the potency of the investigational Sabin IPVs could alter the associations between maternal antibody levels and the serologic responses of infants.

Intranasal and sublingual delivery of inactivated polio vaccine

Polio is on the brink of eradication. Improved inactivated polio vaccines (IPV) are needed towards complete eradication and for the use in the period thereafter. Vaccination via mucosal surfaces has important potential advantages over intramuscular injection using conventional needle and syringe, the currently used delivery method for IPV. One of them is the ability to induce both serum and mucosal immune responses: the latter may provide protection at the port of virus entry. The current study evaluated the possibilities of polio vaccination via mucosal surfaces using IPV based on attenuated Sabin strains. Mice received three immunizations with trivalent sIPV via intramuscular injection, or via the intranasal or sublingual route. The need of an adjuvant for the mucosal routes was investigated as well, by testing sIPV in combination with the mucosal adjuvant cholera toxin. Both intranasal and sublingual sIPV immunization induced systemic polio-specific serum IgG in mice that were functional as measured by poliovirus neutralization. Intranasal administration of sIPV plus adjuvant induced significant higher systemic poliovirus type 3 neutralizing antibody titers than sIPV delivered via the intramuscular route. Moreover, mucosal sIPV delivery elicited polio-specific IgA titers at different mucosal sites (IgA in saliva, fecal extracts and intestinal tissue) and IgA-producing B-cells in the spleen, where conventional intramuscular vaccination was unable to do so. However, it is likely that a mucosal adjuvant is required for sublingual vaccination. Further research on polio vaccination via sublingual mucosal route should include the search for safe and effective adjuvants, and the development of novel oral dosage forms that improve antigen uptake by oral mucosa, thereby increasing vaccine immunogenicity. This study indicates that both the intranasal and sublingual routes might be valuable approaches for use in routine vaccination or outbreak control in the period after complete OPV cessation and post-polio eradication.

Placental antibody transfer efficiency and maternal levels: specific for measles, coxsackievirus A16, enterovirus 71, poliomyelitis I-III and HIV-1 antibodies

Maternal antibodies transported across the placenta can provide vital immunity against infectious pathogens for infants. We here examine maternal antibody (MA) levels and their association with neonatal antibody levels. Pregnant women of gestational age ≥35 weeks were enrolled at a Guangzhou China hospital and mother-infant paired sera were collected. Measles IgG antibody was detected using ELISA assay, neutralizing antibodies titers against coxsackievirus A16 (CA16), enterovirus 71 (EV71), PV I-III and HIV-1 were performed. 711 mother-infant pairs were enrolled and positive relationships for paired serums were found (r: 0.683-0.918). 81.6%, 87.0%, and 82.3% of mothers, and 87.3%, 72.7%, and 72.2% of newborns were positive for measles, CA16 and EV71 antibodies respectively. The highest Neonatal: maternal ratio (NMR) was found in measles (1.042) and the ratios for the other pathogens ranged from 0.84 to 1.00. Linear regressions showed that log(NMR) decreased by a factor of 0.04-15.43 as log(MA) levels increased. A second analysis restricted to maternal positive measles sera revealed that MA measles of was still inversely associated with NMR. Low NMR was found in high MA HIV + serums among 22 paired sera. MA levels appear to play a role determining transplacental antibody transfer; further study is needed to reveal the mechanism.

Adjuvants in micro- to nanoscale: current state and future direction

Adjuvants have been used in vaccines for over 70 years to promote long-lived and sterilizing immunity. Since then, various adjuvant systems were developed by combining nanotechnology with natural and/or synthetic immunomodulatory molecules. These systems are biocompatible, immunogenic, and possess higher antigen carrying capacity. This article showcases advancements made in the adjuvant systems formulations, their synthesis routes, and the improvement of these adjuvants have brought in response to combat against ongoing global health threats such as malaria, hepatitis C, universal influenza, and human immunodeficiency virus. This review also highlights the interaction of adjuvants with the delivery of antigens to cells and unfolds mechanism of actions. In addition, this review discusses the physicochemical factors responsible for the efficient interaction of nanoadjuvants with antigen receptors to develop more effective, less reactogenic, and multifunctional systems for the next generation vaccines.

The potential of nanoparticles for the immunization against viral infections

Vaccination has a great impact on the prevention and control of infectious diseases. However, there are still many infectious diseases for which an effective vaccine is missing. Thirty years after the discovery of the AIDS-pathogen (human immunodeficiency virus, HIV) and intensive research, there is still no protective immunity against the HIV infection. Over the past decade, nanoparticulate systems such as virus-like particles, liposomes, polymers and inorganic nanoparticles have received attention as potential delivery vehicles which can be loaded or functionalized with active biomolecules (antigens and adjuvants). Here we compare the properties of different nanoparticulate systems and assess their potential for the development of new vaccines against a range of viral infections.

Is EU/EEA population protected from polio?

The WHO European Region has been declared polio-free since 2002. By 2010, inactivated polio vaccine (IPV) was the only polio vaccine in use in the EU/EEA for the primary vaccination of children. A systematic review of the literature on polio seroprevalence studies, complemented by the analysis of available vaccine coverage data, has been carried out with the aim of assessing the level of protection against polio in the European population. A total of 52 studies, with data from 14 out of the 31 EU/EEA countries, were included in the analysis. This systematic review shows that, overall, seroprevalence for PV1 and PV3 is high in most countries, although seroimmunity gaps have been detected in several birth cohorts. In particular, relatively low immunity status was found in some countries for individuals born in the 60's and 70's. Discrepancies between reported vaccination coverage and immunity levels have been also highlighted. Countries should make sure that their population is being vaccinated for polio to reduce the risk of local poliovirus transmission in case of importation. Moreover, assessing immunity status should be priority for those traveling to areas where wild polioviruses are still circulating.

Polio endgame: the global introduction of inactivated polio vaccine

In 2013, the World Health Assembly endorsed a plan that calls for the ultimate withdrawal of oral polio vaccines (OPV) from all immunization programs globally. The withdrawal would begin in a phased manner with removal of the type 2 component of OPV in 2016 through a global switch from trivalent OPV to bivalent OPV (containing only types 1 and 3). To mitigate risks associated with immunity gaps after OPV type 2 withdrawal, the WHO Strategic Advisory Group of Experts has recommended that all 126 OPV-only using countries introduce at least one dose of inactivated polio vaccine into routine immunization programs by end-2015, before the trivalent OPV-bivalent OPV switch. The introduction of inactivated polio vaccine would reduce risks of reintroduction of type 2 poliovirus by providing some level of seroprotection, facilitating interruption of transmission if outbreaks occur, and accelerating eradication by boosting immunity to types 1 and 3 polioviruses.

Decay of Sabin inactivated poliovirus vaccine (IPV)-boosted poliovirus antibodies

Introduction

We conducted a follow-on study to a phase I randomized, controlled trial conducted in Cuba, 2012, to assess the persistence of poliovirus antibodies at 21–22 months following booster dose of Sabin-IPV compared to Salk-IPV in adults who had received multiple doses of oral poliovirus vaccine (OPV) during childhood.

Methods

In 2012, 60 healthy adult males aged 19–23 were randomized to receive one booster dose, of either Sabin-inactivated poliovirus vaccine (Sabin-IPV), adjuvanted Sabin-IPV (aSabin-IPV), or conventional Salk-IPV. In the original study, blood was collected at days 0 (before) and 28 (after vaccination), respectively. In this study, an additional blood sample was collected 21–22 months after vaccination, and tested for neutralizing antibodies to Sabin poliovirus types 1, 2 and 3.

Results

We collected sera from 59/60 (98.3%) subjects; 59/59 (100%) remained seropositive to all poliovirus types, 21–22 months after vaccination. The decay curves were very similar among the study groups. Between day 28 and 21–22 months, there was a reduction of ⩾87.4% in median antibody levels for all poliovirus types in all study groups, with no significant differences between the study groups.

Conclusion

The decay of poliovirus antibodies over a 21–22-month period was similar regardless of the type of booster vaccine used, suggesting the scientific data of Salk IPV long-term persistence and decay may be broadly applicable to Sabin IPV.

Development and introduction of inactivated poliovirus vaccines derived from Sabin strains in Japan

During the endgame of global polio eradication, the universal introduction of inactivated poliovirus vaccines is urgently required to reduce the risk of vaccine-associated paralytic poliomyelitis and polio outbreaks due to wild and vaccine-derived polioviruses. In particular, the development of inactivated poliovirus vaccines (IPVs) derived from the attenuated Sabin strains is considered to be a highly favorable option for the production of novel IPV that reduce the risk of facility-acquired transmission of poliovirus to the communities. In Japan, Sabin-derived IPVs (sIPVs) have been developed and introduced for routine immunization in November 2012. They are the first licensed sIPVs in the world. Consequently, trivalent oral poliovirus vaccine was used for polio control in Japan for more than half a century but has now been removed from the list of vaccines licensed for routine immunization. This paper reviews the development, introduction, characterization, and global status of IPV derived from attenuated Sabin strains.

A national reference for inactivated polio vaccine derived from Sabin strains in Japan

As one aspect of its campaign to eradicate poliomyelitis, the World Health Organization (WHO) has encouraged development of the inactivated polio vaccine (IPV) derived from the Sabin strains (sIPV) as an option for an affordable polio vaccine, especially in low-income countries. The Japan Poliomyelitis Research Institute (JPRI) inactivated three serotypes of the Sabin strains and made sIPV preparations, including serotypes 1, 2 and 3 D-antigens in the ratio of 3:100:100. The National Institute of Infectious Diseases, Japan, assessed the immunogenic stability of these sIPV preparations in a rat potency test, according to an evaluation method recommended by the WHO. The immunogenicity of the three serotypes was maintained for at least 4 years when properly stored under -70°C. Based on these data, the sIPV preparations made by JPRI have been approved as national reference vaccines by the Japanese national control authority and used for the quality control of the tetracomponent sIPV-containing diphtheria-tetanus-acellular pertussis combination vaccines that were licensed for a routine polio immunization in Japan.

Next generation inactivated polio vaccine manufacturing to support post polio-eradication biosafety goals

Worldwide efforts to eradicate polio caused a tipping point in polio vaccination strategies. A switch from the oral polio vaccine, which can cause circulating and virulent vaccine derived polioviruses, to inactivated polio vaccines (IPV) is scheduled. Moreover, a manufacturing process, using attenuated virus strains instead of wild-type polioviruses, is demanded to enhance worldwide production of IPV, especially in low- and middle income countries. Therefore, development of an IPV from attenuated (Sabin) poliovirus strains (sIPV) was pursued. Starting from the current IPV production process based on wild type Salk strains, adaptations, such as lower virus cultivation temperature, were implemented. sIPV was produced at industrial scale followed by formulation of both plain and aluminium adjuvanted sIPV. The final products met the quality criteria, were immunogenic in rats, showed no toxicity in rabbits and could be released for testing in the clinic. Concluding, sIPV was developed to manufacturing scale. The technology can be transferred worldwide to support post polio-eradication biosafety goals.