Inactivated Enterovirus 71 Vaccine Produced by 200-L Scale Serum-Free Microcarrier Bioreactor System Provides Cross-Protective Efficacy in Human SCARB2 Transgenic Mouse

Seed Train Optimization in Microcarrier-Based Cell Culture Post In Situ Cell Detachment through Scale-Down Hybrid Modeling

Microcarrier-based cell culture is a commonly used method to facilitate the growth of anchorage-dependent cells like MA 104 for antigen manufacturing. However, conventionally, static cell culture is employed for cell propagation before seeding the production bioreactor with microcarriers (MCs). This study demonstrates the effective replacement of the conventional method by serial subculturing on MCs with in situ cell detachment under optimal conditions in closed culture units. This study proves that MA 104 can be subcultured at least five times on Cytodex 1 MC without the need for separating cells and MC after cell harvest. Process parameters impacting cell growth were studied post in situ cell detachment in a scaled-down model. Optimization, using augmented Design of Experiments (DoE) combined with hybrid modeling, facilitated rapid screening of the design space for critical process parameters (CPPs). Optimized conditions included an inoculation density of >16 cells/bead, 3.5-4.5 g/L of Cytodex 1, and a controlled agitation speed, starting at Njs (minimum agitation speed) for the first day with a maximum increase of 25% thereafter. With these design spaces for CPPs, a cell density of 2.6 ± 0.5 × 106 cells/mL was achieved after five days. This refined bioprocess methodology offers a reliable and efficient approach for seed training in stirred tank reactors, which is particularly beneficial for viral vaccine production.

Research progress on pathogenic and therapeutic mechanisms of Enterovirus A71

In recent years, enterovirus A71 (EV-A71) infection has become a major global public health problem, especially for infants and young children. The results of epidemiological research show that EV-A71 infection can cause acute hand, foot, and mouth disease (HFMD) and complications of the nervous system in severe cases, including aseptic pediatric meningoencephalitis, acute flaccid paralysis, and even death. Many studies have demonstrated that EV-A71 infection may trigger a variety of intercellular and intracellular signaling pathways, which are interconnected to form a network that leads to the innate immune response, immune escape, inflammation, and apoptosis in the host. This article aims to provide an overview of the possible mechanisms underlying infection, signaling pathway activation, the immune response, immune evasion, apoptosis, and the inflammatory response caused by EV-A71 infection and an overview of potential therapeutic strategies against EV-A71 infection to better understand the pathogenesis of EV-A71 and to aid in the development of antiviral drugs and vaccines.

Application of bioreactor technology for cell culture-based viral vaccine production: Present status and future prospects

Bioreactors are widely used in cell culture-based viral vaccine production, especially during the coronavirus disease 2019 (COVID-19) pandemic. In this context, the development and application of bioreactors can provide more efficient and cost-effective vaccine production to meet the global vaccine demand. The production of viral vaccines is inseparable from the development of upstream biological processes. In particular, exploration at the laboratory-scale is urgently required for further development. Therefore, it is necessary to evaluate the existing upstream biological processes, to enable the selection of pilot-scale conditions for academic and industrial scientists to maximize the yield and quality of vaccine development and production. Reviewing methods for optimizing the upstream process of virus vaccine production, this review discusses the bioreactor concepts, significant parameters and operational strategies related to large-scale amplification of virus. On this basis, a comprehensive analysis and evaluation of the various process optimization methods for the production of various viruses (SARS-CoV-2, Influenza virus, Tropical virus, Enterovirus, Rabies virus) in bioreactors is presented. Meanwhile, the types of viral vaccines are briefly introduced, and the established animal cell lines for vaccine production are described. In addition, it is emphasized that the co-development of bioreactor and computational biology is urgently needed to meet the challenges posed by the differences in upstream production scales between the laboratory and industry.

Vero cell upstream bioprocess development for the production of viral vectors and vaccines

The Vero cell line is considered the most used continuous cell line for the production of viral vectors and vaccines. Historically, it is the first cell line that was approved by the WHO for the production of human vaccines. Comprehensive experimental data on the production of many viruses using the Vero cell line can be found in the literature. However, the vast majority of these processes is relying on the microcarrier technology. While this system is established for the large-scale manufacturing of viral vaccine, it is still quite complex and labor intensive. Moreover, scale-up remains difficult and is limited by the surface area given by the carriers. To overcome these and other drawbacks and to establish more efficient manufacturing processes, it is a priority to further develop the Vero cell platform by applying novel bioprocess technologies. Especially in times like the current COVID-19 pandemic, advanced and scalable platform technologies could provide more efficient and cost-effective solutions to meet the global vaccine demand. Herein, we review the prevailing literature on Vero cell bioprocess development for the production of viral vectors and vaccines with the aim to assess the recent advances in bioprocess development. We critically underline the need for further research activities and describe bottlenecks to improve the Vero cell platform by taking advantage of recent developments in the cell culture engineering field.

Enterovirus 71 Infection Shapes Host T Cell Receptor Repertoire and Presumably Expands VP1-Specific TCRβ CDR3 Cluster

Enterovirus 71 (EV71) has become an important public health problem in the Asia-Pacific region in the past decades. EV71 infection might cause neurological and psychiatric complications and even death. Although an EV71 vaccine has been currently approved, there is no effective therapy for treating EV71-infected patients. Virus infections have been reported to shape host T cell receptor (TCR) repertoire. Therefore, understanding of host TCR repertoire in EV71 infection could better the knowledge in viral pathogenesis and further benefit the anti-viral therapy development. In this study, we used a mouse-adapted EV71 (mEV71) model to observe changes of host TCR repertoire in an EV71-infected central nervous system. Neonate mice were infected with mEV71 and mouse brainstem TCRβ repertoires were explored. Here, we reported that mEV71 infection impacted host brainstem TCRβ repertoire, where mEV71 infection skewed TCRβ diversity, changed VJ combination usages, and further expanded specific TCRβ CDR3 clones. Using bioinformatics analysis and ligand-binding prediction, we speculated the expanded TCRβ CDR3 clone harboring CASSLGANSDYTF sequence was capable of binding cleaved EV71 VP1 peptides in concert with major histocompatibility complex (MHC) molecules. We observed that mEV71 infection shaped host TCRβ repertoire and presumably expanded VP1-specific TCRβ CDR3 in mEV71-infected mouse brainstem that integrated EV71 pathogenesis in central nervous system.

Recent advances in the use of microcarriers for cell cultures and their ex vivo and in vivo applications

Microcarriers are 100- to 300-micron support matrices that permit the growth of adherent cells in bioreactor systems. They have a larger surface area to volume ratio in comparison to single cell monolayers, enabling cost-effective cell production and expansion. Microcarriers are composed of a solid matrix that must be separated from expanded cells during downstream processing stages. The detachment method is chosen on the basis of several factors like cell type, microcarrier surface chemistry, cell confluency and degree of aggregation. The development of microcarriers with a range of physiochemical properties permit controlled cell and protein associations that hold utility for novel therapeutics. In this review, we provide an overview of the recent advances in microcarrier cell culture technology. We also discuss its significance as an ex vivo research tool and the therapeutic potential of newly designed microcarrier systems in vivo.

Process optimization for the rapid production of Enterovirus 71

Enterovirus 71 (EV71) infection can cause hand-foot-and-mouth disease (HFMD). Inactivated EV71 vaccine was effective to prevent EV71 derived HFMD. A highly efficient and economical process for producing EV71 is needed. In our study, the epidemic strain of EV71 (EV71-2013ZJHFMD) was obtained and purified. The Vero cells were cultured for production of EV71. The mini-bioreactor vessel (Amprotein Inc., China) packed with a 0.6 g polymer fiber carrier was used to determine the best seeding cell density, multiplicity of infection (MOI) and temperature. Then the optimized procedure was further applied in a 10 L disposable perfusion bioreactor ACPB (AmProtein Current Perfusion Bioreactor). The Vero cell culture and viral titer were monitored. The seeding density of 1.5 × 10⁷ cells per 0.6 g disk was considered to be the most appropriate for the culture. The best MOI was 0.1 and the temperature was 32 °C. The total cell number increased from 1.5 × 10⁹ to 3.0 × 10¹⁰. The maximum viral titers reached 1.0 × 10⁸/mL 3 days post-infection in our optimized special culture procedure (serum-free during the harvest period, supplemented with 0.25% Lactalbumin Hydrolysate). The total volume of the harvested supernatant was 25 L and the total virus yield was 1.93 × 10¹². The procedure using Vero cells grown on polymer fiber paper carriers was effective for the large-scale production of EV71.

Immunogenicity and safety of an inactivated enterovirus A71 vaccine in children 3-6 years and 2-35 months of age- an open-label, randomized phase IIb clinical trial

BACKGROUND

Enterovirus A71 (EV-A71) infection can cause severe debilitating complications and even death in young children. The immunogenicity and safety of an inactivated whole EV-A71 virus vaccine were assessed in children 2 months to 6 years of age.

METHODS

This was an open-label, multi-center and randomized phase IIb study, which divided into part A and B. In part A, children 36 months to 6 years of age were enrolled and randomized into 3 groups, receiving 0.5 μg total viral protein (TP) with adjuvant Al(OH)3, 1.0 μg TP with Al(OH)3 or 1.0 μg TP only. Two doses of vaccines were administered at a 28-day interval and blood was taken before immunization, at week 4, 8, 28 and 52 (optional) for virus neutralization assay. Safety profiles were also monitored. After safety profiles had shown no concerns, children 2 months to 35 months of age (part B) were subsequently enrolled following the same protocol.

RESULTS

A total of 135 children completed two doses of immunization, including 58 in part A and 77 in part B. Both adjuvanted 0.5 μg and 1.0 μg TP elicited significant raise of neutralizing antibody titers and seroconversion rate was up to 93.75-100.0% after 2 doses of immunization. Adjuvanted 1.0 μg TP induced higher titers of neutralizing antibodies than adjuvanted 0.5 μg TP. By contrast, non-adjuvanted 1.0 μg TP was not immunogenic. No major adverse events were reported.

CONCLUSIONS

This EV-A71 vaccine containing adjuvant is immunogenic and safe in children 2 months to 6 years of age.

CLINICAL TRIALS REGISTRATION

NCT03268083.

The mature EV71 virion induced a broadly cross-neutralizing VP1 antibody against subtypes of the EV71 virus

Enterovirus 71 (EV71) has emerged as a neurological virus causing life-threatening diseases in young children and infants. Although EV71 vaccines in development have presented promising results in several clinical trials, the identified key antigen for improving the broad protective efficacy of EV71 vaccines has not been well investigated. In this report, we show that different multiplicities of infection (MOIs) of the B4(E59) virus significantly affect EV71 vaccine production in a serum-free microcarrier bioreactor system. The antigens produced from high MOIs of 10⁻¹ and 10⁻² exhibited higher yield and more infectious full particle (FP) contents in the EV71 vaccines than those produced with low MOIs of 10⁻⁴ and 10⁻⁶, leading to better cross-neutralizing efficacy. The C4(E36) neutralization results showed that only antisera raised from EV71 FPs provided substantial neutralizing titers against C4(E36), whereas empty particles (EPs) of EV71 conferred no efficacy. Competitive ELISA showed that anti-FP mainly binds to FPs and that 20% of antibodies bind to EPs, whereas most anti-EP binds EPs, with only 10% antibodies binding to FPs. VP1-adsorbed anti-FP lost most of the virus neutralization efficiency, suggesting that the VP1 subunit of FP is the major immunogenic antigen determining the ability of the EV71 vaccine to elicit cross-neutralizing antibodies against EV71 virus subtypes. These findings demonstrate that the high-MOI production approach is significantly correlated with FP productivity, thereby improving the cross-neutralization efficacy of an EV71 vaccine and providing the basis for a better vaccine design against widespread EV71 viruses.

Development of a high-growth enterovirus 71 vaccine candidate inducing cross-reactive neutralizing antibody responses

Although Enterovirus 71 (EV71) has only one serotype based on serum neutralization tests using hyperimmune animal antisera, three major genogroups (A, B and C) including eleven genotypes (A, B1-B2, and C1-C5) can be well classified based on phylogenetic analysis. Since 1997, large-scale EV71 epidemics occurred cyclically with different genotypes in the Asia-Pacific region. Therefore, development of EV71 vaccines is a national priority in several Asian countries. Currently, five vaccine candidates have been evaluated in clinical trials in China (three C4 candidates), Singapore (one B2 candidate), and Taiwan (one B4 candidate). Overall, the peak viral titers of these 5 vaccine candidates could only reach about 10⁷ TCID₅₀/mL. Moreover, genotypes of these 5 candidates are different from the current predominant genotype B5 in Taiwan and South-Eastern Asia. We adapted a high-growth EV71 genotype B5 (HG-B5) virus after multiple passages and plaque selections in Vero cells and the HG-B5 virus could reach high titers (>10⁸ TCID₅₀/mL) in a microcarrier-based cell culture system. The viral particles were further purified and formulated with alum adjuvant. After two doses of intramuscular immunization in rabbits, the HG-B5 vaccine candidate could induce cross-reactive neutralizing antibodies against the three major EV71 genogroups. In conclusion, a high-growth EV71 virus was successfully adapted in Vero cells and could induce broad spectrum neutralizing antibody titers against three (A, B5, and C4) genotypes in rabbits.

Mutations in VP1 and 5'-UTR affect enterovirus 71 virulence

Enterovirus 71 (EV71) is a major cause of hand, foot and mouth disease (HFMD). The current EV71 propagating in Vero (EV-V) or sub-passaged in RD (EV-R) cells was used as a pathogen. Interestingly, EV-R exhibited differential virulence; challenging human scavenger receptor class B2-expressing (hSCARB2-Tg) mice with EV71 revealed that EV-V was more virulent than EV-R: 100% of mice that received lethal amounts of EV-V died, while all the mice that received EV-R survived. Severe pathogenesis correlated with viral burdens and proinflammatory cytokine levels were observed in EV-V-challenged mice, but controversy in EV-R-challenged mice. Consensus sequence analysis revealed EV-R rapidly acquired complete mutations at E145G and S241L and partial mutations at V146I of VP1, and acquired a T to C substitution at nucleotide 494 of the 5'-UTR. EV-R exhibited higher binding affinity for another EV71 receptor, human P-selectin glycoprotein ligand-1 (hPSGL-1), than EV-V. Both EV71s exhibited no significant difference in binding to hSCARB2. The molecular modelling indicate that these mutations might influence EV71 engagement with PSGL-1 and in vivo virulence.

A novel multi-peptide subunit vaccine admixed with AddaVax adjuvant produces significant immunogenicity and protection against Proteus mirabilis urinary tract infection in mice model

Proteus mirabilis is a common pathogen in urinary tract infections (UTIs). There is no vaccine against P. mirabilis, thus a novel multi-peptide vaccine of MrpA, UcaA and Pta factors of P. mirabilis we designed and a mice model was used to evaluate its efficacy in combination with AddaVax adjuvant. According to the bioinformatics studies, 7 fragments of MrpA (31-75, 112-146), UcaA (68-117, 132-156) and Pta (210-265, 340-400, 496-570) with B and T cell epitope regions were selected for fusion construction. Mice subcutaneously vaccinated with the fusion MrpA.Pta.UcaA induced a significant increase in serum and mucosal IgG and IgA responses. The fusion also showed a significant induction in cellular responses (Th1 and Th2). The addition of AddaVax to fusion and the mixture of MrpA, UcaA, and Pta (MUP) improved the humoral and cellular responses, especially the IgG2a and IFN-γ (Th1 responses) levels. Fusion with and without AddaVax and MUP + AddaVax could maintain significant humoral responses until 6 months after the first vaccine dose. All vaccine combinations with and without adjuvant showed high effectiveness in the protection of the bladder and kidney against experimental UTI; this could be attributed to the significant humoral and cellular responses. The present study suggests that the AddaVax-based vaccine formulations especially the fusion Pta.MrpA.UcaA admixed with AddaVax as potential vaccine candidates for protection against P. mirabilis. Furthermore, AddaVax could be considered as an effective adjuvant in designing other vaccines against UTI pathogens.

The hUC-MSCs cell line CCRC-1 represents a novel, safe and high-yielding HDCs for the production of human viral vaccines

MRC-5 represents the most frequent human diploid cells (HDCs)-type cell substrate in the production of human viral vaccines. However, early-passage MRC-5 is diminishing and, due to both technical and ethical issues, it is extremely difficult to derive novel HDCs from fetal lung tissues, which are the common sources of HDCs. Our previous studies suggested that human umbilical cord may represent an alternative but convenient source of new HDCs. Here, we established a three-tiered cell banking system of a hUC-MSC line, designated previously as Cell Collection and Research Center-1 (CCRC-1). The full characterization indicated that the banked CCRC-1 cells were free from adventitious agents and remained non-tumorigenic. The CCRC-1 cells sustained its rapid proliferation even at passage 30 and were susceptible to the infection of a wide spectrum of viruses. Interestingly, the CCRC-1 cells showed much higher production of EV71 or Rubella viruses than MRC-5 and Vero cells when growing in serum-free medium. More importantly, the EV71 vaccine produced from CCRC-1 cells induced immunogenicity while eliciting no detectable toxicities in the tested mice. Collectively, these studies further supported that CCRC-1, and likely other hUC-MSCs as well, may serve as novel, safe and high-yielding HDCs for the production of human viral vaccines.

Monolithic anion-exchange chromatography yields rhinovirus of high purity

For vaccine development, 3D-structure determination, direct fluorescent labelling, and numerous other studies, homogeneous virus preparations of high purity are essential. Working with human rhinoviruses (RVs), members of the picornavirus family and the main cause of generally mild respiratory infections, we noticed that our routine preparations appeared highly pure on analysis by sodium dodecyl sulfate polyacrylamide gel electrophoresis (SDS-PAGE), exclusively showing the four viral capsid proteins (VPs). However, the preparations turned out to contain substantial amounts of contaminating material when analyzed by orthogonal analytical methods including capillary zone electrophoresis, nano electrospray gas-phase electrophoretic mobility molecular analysis (nES GEMMA), and negative stain transmission electron microscopy (TEM). Because these latter analyses are not routine to many laboratories, the above contaminations might remain unnoticed and skew experimental results. By using human rhinovirus serotype A2 (RV-A2) as example we report monolithic anion-exchange chromatography (AEX) as a last polishing step in the purification and demonstrate that it yields infective, highly pure, virus (RV-A2 in the respective fractions was confirmed by peptide mass fingerprinting) devoid of foreign material as judged by the above criteria.

DNA vaccines against leptospirosis: A literature review

Leptospirosis is an infectious disease caused by pathogenic Leptospira species. The vaccines that are currently available for leptospirosis are composed of whole-cell preparations and suffer from limitations such as low efficacy, multiple side-effects, poor immunological memory and lack of cross-protection against different serovars of Leptospira spp. In light of the global prevalence of this disease, the development of a more effective vaccine against leptospirosis is of paramount importance. Genetic immunization is a promising alternative to conventional vaccine development. In the last 25years, several novel strategies have been developed for increasing the efficacy of DNA vaccines. Examples of such strategies include the introduction of novel plasmid vectors, adjuvants, alternate delivery routes, and prime-boost regimens. Herein we discuss the latest and most promising advances that have been made in developing DNA vaccines against leptospirosis. We also deliberate over the future directions that must be undertaken in order to improve results in this field.

Impact of genetic changes, pathogenicity and antigenicity on Enterovirus- A71 vaccine development

Enterovirus-A71 (EV-A71) is an etiological agent of the hand, foot and mouth disease (HFMD). EV-A71 infection produces high fever and ulcers in children. Some EV-A71 strains produce severe infections leading to pulmonary edema and death. Although the protective efficacy of the inactivated vaccine (IV) was ≥90% against mild HFMD, there was approximately 80% protection against severe HFMD. The monovalent EV-A71 IV elicits humoral immunity but lacks long-term immunogenicity. Spontaneous mutations of the EV-A71 genome could lead to antigenicity changes and the virus may not be neutralized by antibodies elicited by the IV. A better alternative would be the live attenuated vaccine (LAV) that elicits cellular and humoral immunity. The LAV induces excellent antigenicity and chances of reversion is reduced by presence of multiple mutations which could reduce pathogenicity. Besides CV-A16, outbreaks have been caused by CV-A6 and CV-A10, hence the development of bivalent and trivalent vaccines is required.

Enhancing enterovirus A71 vaccine production yield by microcarrier profusion bioreactor culture

Hand, foot and mouth diseases (HFMD) are mainly caused by Enterovirus A71 (EV-A71) infections. Clinical trials in Asia conducted with formalin-inactivated EV-A71 vaccine candidates produced from serum-free Vero cell culture using either roller bottle or cell factory technology, are found to be safe and highly efficacious. To increase vaccine yields and reduce the production costs, the bioprocess improvement for EV-A71 vaccine manufacturing is currently being investigated. The parameters that could affect and enhance the production yields of EV-A71 virus growth in the microcarrier bioreactor were investigated. The medium replacement culture strategy included a multi-harvested semi-batch process and perfusion technology and was found to increase the production yields more than 7-14 folds. Based on the western blot and cryo-EM analyses of the EV-A71 virus particles produced from either the multi-harvested semi-batch (MHSBC) or perfusion cultures were found to be similar to those virus particles obtained from the single batch culture. Mouse immunogenicity studies indicate that the EV-A71 vaccine candidates produced from the perfusion culture have similar potency to those obtained from single batch bioprocess. The physical structures of the EV-A71 particles revealed by the cryo-EM analysis were found to be spherical capsid particles. These results provide feasible technical bioprocesses for increasing virus yields and the scale up of EV-A71 vaccine manufacturing using the bioreactor cell culture methods.

EV-A71 vaccine licensure: a first step for multivalent enterovirus vaccine to control HFMD and other severe diseases

Enteroviruses (EVs) are the most common viral agents in humans. Although most infections are mild or asymptomatic, there is a wide spectrum of clinical manifestations that may be caused by EV infections with varying degrees of severity. Among these viruses, EV-A71 and coxsackievirus (CV) CV-A16 from group A EVs attract the most attention because they are responsible for hand, foot and mouth disease (HFMD). Other EV-A viruses such as CV-A6 and CV-A10 were also reported to cause HFMD outbreaks in several countries or regions. Group B EVs such as CV-B3, CV-B5 and echovirus 30 were reported to be the main pathogens responsible for myocarditis and encephalitis epidemics and were also detected in HFMD patients. Vaccines are the best tools to control infectious diseases. In December 2015, China's Food and Drug Administration approved two inactivated EV-A71 vaccines for preventing severe HFMD.The CV-A16 vaccine and the EV-A71-CV-A16 bivalent vaccine showed substantial efficacy against HFMD in pre-clinical animal models. Previously, research on EV-B group vaccines was mainly focused on CV-B3 vaccine development. Because the HFMD pathogen spectrum has changed, and the threat from EV-B virus-associated severe diseases has gradually increased, it is necessary to develop multivalent HFMD vaccines. This study summarizes the clinical symptoms of diseases caused by EVs, such as HFMD, myocarditis and encephalitis, and the related EV vaccine development progress. In conclusion, developing multivalent EV vaccines should be strongly recommended to prevent HFMD, myocarditis, encephalitis and other severe diseases.

Development of a full-length cDNA-derived enterovirus A71 vaccine candidate using reverse genetics technology

Enterovirus A71 (EV-A71) is responsible for epidemics of hand, foot and mouth disease (HFMD) in young children. To circumvent difficulties in obtaining clinical enterovirus isolates that might be contaminated with other viruses, a platform technology was developed to quickly generate vaccine virus strains based on the published enterovirus genomic sequences. A recombinant plasmid containing the full-length infectious cDNA clone of EV-A71 vaccine strain E59 was directly generated after transfecting the recombinant plasmid into Vero, RD or HEK293A cells, and phenotypic characteristics similar to the parental strain were observed. The cDNA-derived infectious EV-A71 virus grown in Vero cells produced relatively stable virus titers in both T-flasks and microcarrier culture systems. To evaluate the genetic stability of the cDNA-derived EV-A71 viruses, the immunodominant structural proteins, VP1 and VP2, of the recombinant EV-A71 viruses were sequenced and analyzed. The cDNA-derived EV-A71 virus showed weak pathogenicity in a human SCARB2 mouse model. These results show the successful generation of a recombinant virus derived from a published viral genomic sequence that demonstrated good genetic stability and viral yields, which could represent an efficient and safe vaccine strain for cGMP-grade manufacturing.

EV71 vaccine, a new tool to control outbreaks of hand, foot and mouth disease (HFMD)

On December 3rd 2015, the China Food and Drug Administration (CFDA) approved the first inactivated Enterovirus 71 (EV71) whole virus vaccine for preventing severe hand, foot and mouth disease (HFMD). As one of the few preventive vaccines for children's infectious diseases generated by the developing countries in recent years, EV71 vaccine is a blessing to children's health in China and worldwide. However, there are still a few challenges facing the worldwide use of EV71 vaccine, including the applicability against various EV71 pandemic strains in other countries, international requirements on vaccine production and quality control, standardization and harmonization on different pathogen monitoring and detecting methods, etc. In addition, the affordability of EV71 vaccine in other countries is a factor to be considered in HFMD prevention. Therefore, with EV71 vaccine commercially available, there is still a long way to go before reaching effective protection against severe HFMD after EV71 vaccines enter the market. In this paper, the bottlenecks and prospects for the wide use of EV71 vaccine after its approval are evaluated.