Advances in Zika virus vaccines and therapeutics:A systematic review

Zika virus(ZIKV)is the causative agent of a viral infection that causes neurological complications in newborns and adults worldwide.Its wide transmission route and alarming spread rates are of great concern to the scientific community.Numerous trials have been conducted to develop treatment options for ZIKV infection.This review highlights the latest developments in the fields of vaccinology and pharmaceuticals developments for ZIKV infection.A systematic and comprehensive approach was used to gather relevant and up-to-date data so that inferences could be made about the gaps in therapeutic development.The results indicate that several therapeutic interventions are being tested against ZIKV infection,such as DNA vaccines,subunit vaccines,live-attenuated vaccines,virus-vector-based vaccines,inactivated vaccines,virus-like particles,and mRNA-based vaccines.In addition,approved anti-ZIKV drugs that can reduce the global burden are discussed.Although many vaccine candidates for ZIKV are at different stages of development,none of them have received Food and Drug Authority approval for use up to now.The issue of side effects associated with these drugs in vulnerable newborns and pregnant women is a major obstacle in the therapeutic pathway.

Recent advances on vaccines against malaria: A review

This review aims to summarize the currently viable vaccine strategies including the approved vaccines and the those in trials for next-generation malaria vaccines.Data on malaria vaccine development was collected through a comprehensive review.The literature search was performed using databases including Google Scholar,PubMed,NIH,and Web of Science.Various novel approaches of vaccination are being developed,including those based on radiation-attenuated strategies,monoclonal antibodies,targeted immunogenic peptides,RNA and DNA vaccines,nanoparticle-based vaccines,protein-based vaccination protocols,and whole organism-based vaccination strategies.Trials on RTS,S have entered phase Ⅲtesting,and those based on blood-stage vaccines and vaccines to interrupt malarial transmission have advanced to higher stages of trials.Mathematical modeling,combined drug and vaccine strategies,mass drug administration,polyvalent vaccine formulations,and targeted vaccination campaigns is playing an important role in malarial prevention.Furthermore,assessing coverage,accessibility,acceptability,deployment,compilation,and adherence to specific vaccination strategies in endemic regions is essential for vaccination drives against malaria.

Rotavirus, Norovirus and Astrovirus in Children Aged 0 - 5 Years: Evolution of Prevalence over 10 Years (2013-2023) Following the Introduction of Rotavirus Vaccines in Burkina Faso

Rotaviruses, noroviruses, and astroviruses are responsible for gastroenteritis in children under 5 years old. The objective of our study was to estimate the evolution of prevalence of rotavirus, norovirus and astrovirus infections in children aged 0 to 5 years with gastroenteritis, after the introduction of rotavirus vaccines in Burkina Faso. This cross-sectional study was conducted between January and December 2023, collecting 100 stool samples from children with gastroenteritis at Saint Camille Hospital in Ouagadougou and the Charles De Gaulle University Paediatric Hospital. Noroviruses and astroviruses were detected using multiplex real-time PCR with a Sacace biotechnology detection kit. Data analysis was performed with Stata statistical software, version 16.0. The prevalence of norovirus infections was 14% and astrovirus infections were 9%. Rotavirus infections were found at prevalence of 15%. The age group most affected by norovirus and astrovirus infections was 0 - 12 months, with respective prevalence rates of 73.34% and 55.56%. The most frequently observed clinical signs in children infected with astrovirus were fever (77.78%), diarrhea (55.56%), and vomiting (44.44%). The introduction of rotavirus vaccines has reduced rotavirus-related infections. However, this has not significantly impacted the prevalence of norovirus and astrovirus infections in Burkina Faso.

mRNA vaccines:a new era in vaccine development

The advent of RNA therapy,particularly through the development of mRNA cancer vaccines,has ushered in a new era in the field of oncology.This article provides a concise overview of the key principles,recent advancements,and potential implications of mRNA cancer vaccines as a groundbreaking modality in cancer treatment.mRNA cancer vaccines represent a revolutionary approach to combatting cancer by leveraging the body’s innate immune system.These vaccines are designed to deliver specific mRNA sequences encoding cancer-associated antigens,prompting the immune system to recognize and mount a targeted response against malignant cells.This personalized and adaptive nature of mRNA vaccines holds immense potential for addressing the heterogeneity of cancer and tailoring treatments to individual patients.Recent breakthroughs in the development of mRNA vaccines,exemplified by the success of COVID-19 vaccines,have accelerated their application in oncology.The mRNA platform’s versatility allows for the rapid adaptation of vaccine candidates to various cancer types,presenting an agile and promising avenue for therapeutic intervention.Clinical trials of mRNA cancer vaccines have demonstrated encouraging results in terms of safety,immunogenicity,and efficacy.Pioneering candidates,such as BioNTech’s BNT111 and Moderna’s mRNA-4157,have exhibited promising outcomes in targeting melanoma and solid tumors,respectively.These successes underscore the potential of mRNA vaccines to elicit robust and durable anti-cancer immune responses.While the field holds great promise,challenges such as manufacturing complexities and cost considerations need to be addressed for widespread adoption.The development of scalable and cost-effective manufacturing processes,along with ongoing clinical research,will be pivotal in realizing the full potential of mRNA cancer vaccines.Overall,mRNA cancer vaccines represent a cutting-edge therapeutic approach that holds the promise of transforming cancer treatment.As research progresses,addressing challenges and refining manufacturing processes will be crucial in advancing these vaccines from clinical trials to mainstream oncology practice,offering new hope for patients in the fight against cancer.

Neoantigen cancer vaccines:a new star on the horizon

Immunotherapy represents a promising strategy for cancer treatment that utilizes immune cells or drugs to activate the patient's own immune system and eliminate cancer cells.One of the most exciting advances within this field is the targeting of neoantigens,which are peptides derived from non-synonymous somatic mutations that are found exclusively within cancer cells and absent in normal cells.Although neoantigen-based therapeutic vaccines have not received approval for standard cancer treatment,early clinical trials have yielded encouraging outcomes as standalone monotherapy or when combined with checkpoint inhibitors.Progress made in high-throughput sequencing and bioinformatics have greatly facilitated the precise and efficient identification of neoantigens.Consequently,personalized neoantigen-based vaccines tailored to each patient have been developed that are capable of eliciting a robust and long-lasting immune response which effectively eliminates tumors and prevents recurrences.This review provides a concise overview consolidating the latest clinical advances in neoantigen-based therapeutic vaccines,and also discusses challenges and future perspectives for this innovative approach,particularly emphasizing the potential of neoantigen-based therapeutic vaccines to enhance clinical efficacy against advanced solid tumors.

Overcoming neutrophil-induced immunosuppression in postoperative cancer therapy: Combined sialic acid-modified liposomes with scaffold-based vaccines

Immunotherapy is a promising approach for preventing postoperative tumor recurrence and metastasis. However, inflammatory neutrophils, recruited to the postoperative tumor site, have been shown to exacerbate tumor regeneration and limit the efficacy of cancer vaccines. Consequently, addressing postoperative immunosuppression caused by neutrophils is crucial for improving treatment outcomes. This study presents a combined chemoimmunotherapeutic strategy that employs a biocompatible macroporous scaffold-based cancer vaccine (S-CV) and a sialic acid (SA)-modified, doxorubicin (DOX)-loaded liposomal platform (DOX@SAL). The S-CV contains whole tumor lysates as antigens and imiquimod (R837, Toll-like receptor 7 activator)-loaded PLGA nanoparticles as immune adjuvants for cancer, which enhance dendritic cell activation and cytotoxic T cell proliferation upon localized implantation. When administered intravenously, DOX@SAL specifically targets and delivers drugs to activated neutrophils in vivo, mitigating neutrophil infiltration and suppressing postoperative inflammatory responses. In vivo and vitro experiments have demonstrated that S-CV plus DOX@SAL, a combined chemo-immunotherapeutic strategy, has a remarkable potential to inhibit postoperative local tumor recurrence and distant tumor progression, with minimal systemic toxicity, providing a new concept for postoperative treatment of tumors.

Plant-based vaccines against viral hepatitis: A panoptic review

The traditional vaccines against hepatitis have been instrumental in reducing the incidence of some types of viral hepatitis;however,the need for cost-effective,easily distributable,and needle-free vaccine alternatives has led to the exploration of plant-based vaccines.Plant-based techniques offer a promising avenue for producing viral hepatitis vaccines due to their low-cost cultivation,scalability,and the potential for oral administration.This review highlights the successful expression of hepatitis B surface antigens in plants and the subsequent formation of virus-like particles,which have shown immunogenicity in preclinical and clinical trials.The challenges such as achieving sufficient antigen expression levels,ensuring consistent dosing,and navigating regulatory frameworks,are addressed.The review considers the potential of plant-based vaccines to meet the demands of rapid vaccine deployment in response to outbreaks and their role in global immunization strategies,particularly in resource-limited settings.This review underscores the significant strides made in plant molecular farming and the potential of plant-based vaccines to complement existing immunization methods against viral hepatitis.

Toward innovative veterinary nanoparticle vaccines

Nanoparticles are significant for veterinary vaccine development because they are safer and more effective than conventional formulations.One promising area of research involves self-assembled protein nanoparticles(SAPNs),which have shown potential for enhancing antigen-presenting cell uptake,B-cell activation,and lymph node trafficking.Numerous nanovaccines have been utilized in veterinary medicine,including natural self-assembled protein nanoparticles,rationally designed self-assembled protein nanoparticles,animal virus-derived nanoparticles,bacteriophagederived nanoparticles,and plant-derived nanoparticles,which will be discussed in this review.SAPN vaccines can produce robust cellular and humoral immune responses and have been shown to protect against various animal infectious diseases.This article attempts to summarize these diverse nanovaccine types and their recent research progress in the field of veterinary medicine.Furthermore,this paper highlights their disadvantages and methods for improving their immunogenicity.

Analysis of Public Sentiment regarding COVID-19 Vaccines on the Social Media Platform Reddit

This study undertakes a thorough analysis of the sentiment within the r/Corona-virus subreddit community regarding COVID-19 vaccines on Reddit. We meticulously collected and processed 34,768 comments, spanning from November 20, 2020, to January 17, 2021, using sentiment calculation methods such as TextBlob and Twitter-RoBERTa-Base-sentiment to categorize comments into positive, negative, or neutral sentiments. The methodology involved the use of Count Vectorizer as a vectorization technique and the implementation of advanced ensemble algorithms like XGBoost and Random Forest, achieving an accuracy of approximately 80%. Furthermore, through the Dirichlet latent allocation, we identified 23 distinct reasons for vaccine distrust among negative comments. These findings are crucial for understanding the community’s attitudes towards vaccination and can guide targeted public health messaging. Our study not only provides insights into public opinion during a critical health crisis, but also demonstrates the effectiveness of combining natural language processing tools and ensemble algorithms in sentiment analysis.

An Overview of Quality Management of Therapeutic Vaccines in Clinical Trials in China

Objective To provide suggestions and a reference for improving the quality management system of clinical trials of therapeutic vaccines and promoting the development of therapeutic vaccines in China.Methods Literature research,case study and comparative study were used to analyze the quality management system of clinical trials of therapeutic vaccines.Results and Conclusion From the perspective of the sponsor,investigators and the thirdparty technical service company,the problems such as the low efficiency of clinical trial sample preparation and the lax implementation of the protocol by hospital departments in the quality management of clinical trials of therapeutic vaccines in China were found.Then,the optimization plan for the quality management of clinical trials of therapeutic vaccines is proposed,including optimizing the preparation process of therapeutic vaccines and strengthening the training of hospital department personnel.

Protective Efficacy of Newcastle Disease Vaccines against Prevalent Strains in Recent Years

[Objective] To investigate the protective efficacy of currently available Newcastle disease vaccines against currently prevalent strains and thus provide guidance for the application of vaccines and the prevention and control of Newcastle disease. E Method] The 6-week-old SPF chickens were respectively inoculated with five live attenuated Newcastle disease vaccines （A, B, C, D, and E） at the dose of 1-fold or 0.01-fold usage via intranasal, intraocular or oral route. After 14 d post immunization, the titers of HI antibody were detected. And all the chickens were chal- lenged by Newcastle disease virus （NDV） FEo standard strain or the isolated wild strains, NDV-2007-HB and NDV-2008-YB. The clinical symptoms of chickens were continuously observed, and the morbidity and mortality were determined. [ Resalt] After 14 d post immunization, antibodies were induced at a protective level in chickens immunized with the five vaccines. As shown by the animal experiment, the five vaccines at the dose of 1-fold or 0.01-fold usage protected all vaccinated chickens from the death caused by NDV strain, and more than 90% of vaccinated chick- ens from the death caused by NDV-2007-HB strain, while the vaccines, A, B, and C, at the dose of 0.01 -fold usage protected more than 90% of vaccinated chickens from the death caused by NDV-2008-YB strain. E Conclusion] Under laboratory conditions, the currently available Newcastle disease vaccines have better protective efficacy against the two currently prevalent NDV strains and prevent the occurrence of Newcastle disease.

Progress in the development of vaccines for hepatitis C virus infection

The hepatitis C virus(HCV), first described in 1989, is now a leading cause of liver cirrhosis and hepatocellular carcinoma. With more than 170 million people infected globally, this virus is a major public health issue. The current standard therapy is based on interferon in combination with ribavirin. This costly therapy often fails to completely clear the infection and is associated with adverse side effects. Recent anti-HCV therapies are interferon-free direct-acting antiviral(DAA) regimens for HCV, including simeprevir, sofosbuvir, and ledipasvir, which have effects on non-structural proteins. DAA regimens have several advantages, such as specifically targeting HCV viral replication, accompanied by very high sustained virological response rates and lower side effects like flu-like syndrome. These facts plus the fact that most HCV cases progress to chronic infection suggest the potential need for an efficient HCV vaccine. Different innovative methods, including methods based on peptide, recombinant protein, DNA, vector-based, and virus-like particles, have been introduced for the development of HCV vaccines. An extensive number of studies have been published on these vaccines, and some vaccines were even tested in clinical trials. In the current review, progress in the development of preventive and therapeutic vaccines against the HCV is reviewed in the context of peptide vaccines, recombinant protein vaccines, HCV-like particle, DNA vaccines and viral vectors expressing HCV genes.

H2 strain attenuated live hepatitis A vaccines:protective efficacy in a hepatitis A outbreak

AIM:To investigate the protective efficacy of H2 strain attenuated live hepatitis A vaccines (H2-strain vaccines) in hepatitis A (HA) outbreaks.METHODS:With the permission of their parents, 5551 pre-school and grade 1-3 primary school children were inoculated with 1 dose (10(6.5) TCID(50)) of H2 strain vaccines in a nonrandomized, controlled trial conducted in Fucheng County, Hebei Province in May 1997.Another 6485 children in the same grades and compatible in gender and age were enrolled as controls. Epidemiological and serological survey was conducted to evaluate the protective efficacy of the vaccines. ELISA was used to detect serum IgM anti-HAV.RESULTS:HA outbreak started in early May 1998, peaked in the middle of the same month, and lasted about 80 days. Overall 302 HA cases were found, 192(63.58%) were 5-9 years old. One vaccinee and 25 control cases were found to have hepatitis A, which account for 0.28% (1/356) and 5.92% (25/422) of all vaccinees and controls in the 14 villages, respectively. The protective efficacy of vaccines was 95.27% (95% CI: 85.83%-104.72%). In subjects tested for anti-HAV IgM from 13 villages, 1(0.40%) overt and 11(4.06%) asymptomatic HAV cases were found in 271 vaccinees but 21(6.69%) of overt and asymptomatic ones were found in 314 controls.CONCLUSION:H2 strain vaccines were excellent in preventing overt hepatitis A,but not so effective in preventing asymptomatic hepatitis A virus infection.A booster dose might be needed to get permanent reliable immunity.

HBsAg, HBcAg, and combined HBsAg/HBcAg-based therapeutic vaccines in treating chronic hepatitis B virus infection

BACKGROUND: As the host immunity is diminished in patients with chronic hepatitis B (CHB), different approaches have been used to up-regulate their immune responses to produce therapeutic effects. But, cytokines, growth factors and polyclonal immune modulators could not exhibit sufficient therapeutic effects in these patients. Immune therapy with HBV-related antigens (vaccine therapy) has been used in CHB patients. But there is a paucity of information about the design of HBV antigen-based immune therapy in these patients. DATA SOURCE: Preclinical and clinical studies on immune therapy with HBsAg-based vaccine, HBcAg and combination of HBsAg/HBcAg-based vaccines have been discussed. RESULTS: HBsAg-based prophylactic vaccine was used as an immune therapeutic agent in CHB patients; however, monotherapy with HBsAg-based immune therapy could not lead to sustained control of HBV replication and/or liver damages. HBsAg-based vaccine was used as a combination therapy with cytokines, growth factors, and antiviral drugs. HBsAg-based vaccine was also used for cell-based therapy. However, satisfactory therapeutic effects of HBsAg-based vaccine could not be documented in CHB patients. In the mean time, evidences have supported that HBcAg-specific immunity is endowed with antiviral and liver protecting capacities in CHB patients. Recent data concentrate on the clinical use of combined HBsAg- and HBcAg-based vaccines in CHB patients.CONCLUSION: Antigen-based immune therapy with HBV- related antigens may be an alternative method for the treatment of CHB patients but proper designs of antigens, types of adjuvants, dose of vaccinations, and routes of administration need further analyses for the development of an effective regimen of immune therapy against HBV.

Regulating Effects of Novel CpG Chitosan-nanoparticles on Immune Responses of Mice to Porcine Paratyphoid Vaccines

Objective To study the regulating effects of a novel CpG oligodeoxynuleotide and the synergistic effect of chitosan-nanoparticles （CNP） with CpG on immune responses of mice, which were used to develop a novel immunoadjuvant to boost immune response to conventional vaccines. Methods A novel CpG ODN containing 11 CpG motifs was synthesized and its bioactivities to stimulate the proliferation of lymphocytes of pig in vitro were detected. Then it was entrapped with CNP prepared in our laboratory by the method of ionic cross linkage, and immunized Kunming mice were co-inoculated with paratyphoid vaccine. The peripheral blood was collected weekly from the tail vein of inoculated mice to detect the contents of IgG, IgA, IgM, and specific antibody against salmonella as well as the levels of interleukin-2 （IL2）, IL-4, and IL-6 by SABC-ELISA assay. The numbers of leucocytes, monocytes, granuloytes, and lymphocytes were calculated separately using the routine method. The experimental mice were orally challenged with virulent salmonella 35 days after inoculation. Results This CpG ODN could remarkably provoke the proliferation of lymphocytes of pig in vitro in contrast with the control （P〈0.05）. Compared with those of the control, immunoglobulins, including IgG, IgA, IgM, and specific antibodies to paratyphoid vaccine, increased significantly in sera from the CpG or CpG-CNP-vaccinated mice （P〈0.05）. IL-2, IL-4, and IL-6 increased remarkably in sera from immunized mice （P〈0.05）. The leucocytes, monocytes, granuloytes, and lymphocytes of the mice immunized with CpG or CpG-CNP were also increased in number （P〈0.05）. After the challenge, these immunity values were elevated in the mice vaccinated with CpG or CpG-CNP. The immunized mice all survived, while the control mice fell ill with evident lesions with diffuse hemorrhage in stomach, small intestine, and peritoneum. Conclusions CpG ODN entrapped with CNP is a promising effective immunoadjuvant for vaccination, which promotes humoral and cellular immune responses, enhances immunity and resistance against salmonella by co-administration with paratyphoid vaccine. Key words：

Colorectal cancer vaccines: Tumor-associated antigens vs neoantigens

Therapeutic options for the treatment of colorectal cancer(CRC) are diverse but still not always satisfying. Recent success of immune checkpoint inhibition treatment for the subgroup of CRC patients suffering from hypermutated tumors suggests a permanent role of immune therapy in the clinical management of CRC. Substantial improvement in treatment outcome could be achieved by development of efficient patient-individual CRC vaccination strategies. This mini-review summarizes the current knowledge on the two general classes of targets: tumor-associated antigens(TAAs) and tumorspecific antigens. TAAs like carcinoembryonic antigen and melanoma associated antigen are present in and shared by a subgroup of patients and a variety of clinical studies examined the efficacy of different TAA-derived peptide vaccines. Combinations of several TAAs as the next step and the development of personalized TAA-based peptide vaccines are discussed. Improvements of peptidebased vaccines achievable by adjuvants and immunestimulatory chemotherapeutics are highlighted. Finally, we sum up clinical studies using tumor-specific antigens-in CRC almost exclusively neoantigens-which revealed promising results; particularly no severe adverse events were reported so far. Critical progress for clinical outcomes can be expected by individualizing neoantigen-based peptide vaccines and combining them with immunestimulatory chemotherapeutics and immune checkpoint inhibitors. In light of these data and latest developments, truly personalized neoantigen-based peptide vaccines can be expected to fulfill modern precision medicine's requirements and will manifest as treatment pillar for routine clinical management of CRC.

Relationship between T-lymphocyte cytokine levels and sero-response to hepatitis B vaccines

AIM: To investigate the cellular defects by analyzing the (Th1/Th2) cytokine levels in vaccine responders and non-responders. METHODS: Peripheral blood mononuclear cell (PBMC) from responders and non-responders were stimulated with or with out recombinant HBsAg or PHA. Broad spectrum of cytokines viz (Th1) IFN-γ, IL-2, TNF-α, IL-12 and (Th2) IL-10, IL-4 were measured after in vitro stimulation with recombinant HBsAg and were compared with respective antibody titers. RESULTS: A significant decrease (P = 0.001) in Th1 and Th2 cytokines namely, IL-2, INF-γ, TNF-α and IL-10in non-responders was observed. The level of IL-4 was not significant between the three groups. Furthermore, despite a strong Th1 and Th2 cytokine response, the level of IL-12 was elevated in high-responders compared to other groups (P = 0.001) and demonstrated a positive correlation with anti-HBs titers and Th1 cytokine response. CONCLUSION: Our findings suggest that unrespon-siveness to recombinant hepatitis B vaccines (rHB) is multifactorial, including specific failure of antigen presentation or the lack of both T helper Th1 and Th2 response.

Recent advances in heat shock protein-based cancer vaccines

BACKGROUND: Active immunotherapy has been successful in preventing many infectious diseases, and is being explored for its anti-tumor use. Purified antigens, peptides, gene-based systems and antigens contained in whole cells or cell lysates are used in specific active immunotherapy for cancer, known as cancer vaccines. Cancer vaccines do not directly kill tumor cells, but prime a specific humoral and/or cellular immune response against the tumor. Up to date, many kinds of cancer vaccines have been tested in the world and have shown their own advantages. Heat shock protein (HSP)-based cancer vaccine is one of the outstanding representatives. In this paper, we review recent advances in HSP-based cancer vaccines. DATA SOURCES: An English-language literature search was conducted using MEDLINE (1990-2005) on HSP, cancer vaccines and other related subjects. RESULTS: Several kinds of HSP-based cancer vaccines which have been explored worldwide, include tumor derived HSP-pepdde complex cancer vaccines, artificially reconstituted HSP-peptide complex cancer vaccines, HSPpeptide fusion protein cancer vaccines and HSP-based DNA cancer vaccines, etc. Many HSP-based cancer vaccines are being tested in clinical trials, and some are being tested in phase Ⅲ clinical trials at present. CONCLUSION: The available results in preclinical tests and clinical trials indicate that HSP-based cancer vaccines are promising in cancer therapy.

Immunotherapy and therapeutic vaccines in prostate cancer： an update on current strategies and clinical implications

In recent years, immunotherapy has emerged as a viable and attractive strategy for the treatment of prostate cancer. While there are multiple ways to target the immune system, therapeutic cancer vaccines and immune checkpoint inhibitors have been most successful in late-stage clinical trials. The landmark Food and Drug Administration approval of sipuleuceI-T for asymptomatic or minimally symptomatic metastatic prostate cancer set the stage for ongoing phase III trials with the cancer vaccine PSA-TRICOM and the immune checkpoint inhibitor ipilimumab. A common feature of these immune-based therapies is the appearance of improved overall survival without short-term changes in disease progression. This class effect appears to be due to modulation of tumor growth rate kinetics, in which the activated immune system exerts constant immunologic pressure that slows net tumor growth. Emerging data suggest that the ideal population for clinical trials of cancer vaccines is patients with lower tumor volume and less aggressive disease. Combination strategies that combine immunotherapy with standard therapies have been shown to augment both immune response and clinical benefit.

Porcine reproductive and respiratory syndrome virus vaccines: Immunogenicity, efficacy and safety aspects

Porcine reproductive and respiratory syndrome virus(PRRSV) infection is the leading cause of economic casualty in swine industry worldwide. The virus can cause reproductive failure, respiratory disease, and growth retardation in the pigs. This review deals with current status of commercial PRRS vaccines presently used to control PRRS. The review focuses on the immunogenicity, protective efficacy and safety aspects of the vaccines. Commercial PRRS modified-live virus(MLV) vaccine elicits delayed humoral and cell-mediated immune responses following vaccination. The vaccine confers late but effective protection against genetically homologous PRRSV, and partial protection against genetically heterologous virus. The MLV vaccine is of concern for its safety as the vaccine virus can revert to virulence and cause diseases. PRRS killed virus(KV) vaccine, on the other hand, is safe but confers limited protection against either homologous or heterologous virus. The KV vaccine yet helps reduce disease severity when administered to the PRRSV-infected pigs. Although efforts have been made to improve the immunogenicity, ef-ficacy and safety of PRRS vaccines, a better vaccine is still needed in order to protect against PRRSV.