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At least 19 recordsLinked to original sources
PubMed2025

Malaria: Factors affecting disease severity, immune evasion mechanisms, and reversal of immune inhibition to enhance vaccine efficacy.

Malaria is a complex parasitic disease caused by species of Plasmodium parasites. Infection with the parasites can lead to a spectrum of symptoms and disease severity, influenced by various parasite, host, and environmental factors. There have been some successes in developing vaccines against the disease recently, but the vaccine efficacies require improvement. Some issues associated with the difficulties in developing a sterile vaccine include high antigenic diversity, switching expression of the immune targets, and inhibition of immune pathways. Current vaccine research focuses on identifying conserved and protective epitopes, developing multivalent vaccines (including the whole parasite), and using more powerful adjuvants. However, overcoming the systematic immune inhibition and immune cell dysfunction/exhaustion may be required before high titers of protective antibodies can be achieved. Increased expression of surface molecules such as CD86 and MHC II on antigen-presenting cells and blocking immune checkpoint pathways (interactions of PD-1 and PD-L1; CTLA-4 and CD80) using small molecules could be a promising approach for enhancing vaccine efficacy. This assay reviews the factors affecting the disease severity, the genetics of host-parasite interaction, immune evasion mechanisms, and approaches potentially to improve host immune response for vaccine development.

Humans↗
PubMed2025

Vaccine efficacy of NVX-CoV2373 against SARS-CoV-2 infection in adolescents in the USA: an ancillary study to a phase 3, observer-blinded, randomised, placebo-controlled trial.

BACKGROUND: Although existing COVID-19 vaccines are known to be highly effective against severe disease and death, data are needed to assess their ability to reduce SARS-CoV-2 infection. We aimed to estimate the efficacy of the NVX-CoV2373 protein subunit vaccine against SARS-CoV-2 infection, regardless of symptoms, among adolescents. METHODS: We performed an ancillary observational study (SNIFF) to the phase 3, observer-blinded, randomised, placebo-controlled PREVENT-19 trial that assessed vaccine efficacy against symptomatic COVID-19 in the USA. Participants in the PREVENT-19 trial included healthy adolescents aged 12-17 years and with no history of laboratory-confirmed SARS-CoV-2 infection. They were randomly assigned (2:1) to receive either the NVX-CoV2373 (Novavax, Gaithersburg, MD, USA) vaccine (immediate NVX-CoV2373 group) or placebo (delayed NVX-CoV2373 group) on days 0 and 21 (initial series). After 2 months, in a crossover series, participants received two doses, 21 days apart, of the intervention that they did not receive in their initial series. Participants at 47 of the PREVENT-19 sites were invited to participate in the SNIFF study and self-collect nasal swabs at home twice weekly for SARS-CoV-2 testing to assess vaccine efficacy against SARS-CoV-2 infection. This primary outcome was defined as the first identification of SARS-CoV-2 detected by RT-PCR, regardless of symptoms, with onset within 4 weeks after the second dose of the initial vaccination series until the second dose of the crossover series. Secondary outcomes were vaccine efficacy against asymptomatic and minimally symptomatic SARS-CoV-2 infection, durability of vaccine efficacy against SARS-CoV-2 infection, and durability of vaccine efficacy against asymptomatic and minimally symptomatic infections. Outcomes were analysed in the modified intention-to-treat population, which included all participants without previous SARS-CoV-2 infection and was restricted to participants enrolled within 4 weeks of the second dose of the primary (primary analysis population) or crossover (post-crossover analysis population) series. This study is registered with ClinicalTrials.gov (NCT04611802). FINDINGS: Between June 1 and Dec 17, 2021, 1196 (53·2%) of the 2247 adolescent participants recruited in the PREVENT-19 trial enrolled in the SNIFF study. The primary analysis population included 471 participants in the immediate NVX-CoV2373 group and 220 in the delayed NVX-CoV2373 group. Incidence of SARS-CoV-2 infection was 14·9 cases per 100 person-years (95% CI 7·9-25·5) in the immediate group and 54·2 cases per 100 person-years (33·6-82·9) in the delayed group; vaccine efficacy was 73·5% (95% CI 47·1-86·7; p=0·0002). Incidence of minimally symptomatic or asymptomatic SARS-CoV-2 infection was 10·3 cases per 100 person-years (95% CI 4·7-19·6) in the immediate group and 36·1 cases per 100 person-years (19·8-60·7) in the delayed group; vaccine efficacy was 72·8% (95% CI 37·1-88·2; p=0·0023). After the second crossover dose, incidence of SARS-CoV-2 was 14·6 cases per 100 person-years (95% CI 8·6-23·0) in the immediate group (receiving placebo at crossover) and 9·1 cases per 100 person-years (3·0-21·3) in the delayed group, with a durability ratio of 160·3 (95% CI 59·5-431·6; p=0·35). Almost all infections after crossover were minimally symptomatic or asymptomatic, with a durability ratio of 151·4 (55·9-410·4; p=0·41). INTERPRETATION: Among adolescents participating in the PREVENT-19 trial during the delta (B.1.617.2) variant wave of the COVID-19 pandemic, the NVX-CoV2373 vaccine was highly efficacious against SARS-CoV-2 infection regardless of symptoms, indicating its potential to reduce the reservoir of infections that contribute to community transmission. FUNDING: US Department of Health and Human Services, Administration for Strategic Preparedness and Response, Biomedical Advanced Research and Development Authority, National Institute of Allergy and Infectious Diseases, and National Institutes of Health.

Adolescent↗
PubMed2026

Evaluation of transduction properties and vaccine efficacy of a simian adenovirus type 25-based vector.

Although human adenovirus serotype 5 (Ad5) is widely used as a vaccine vector for infectious diseases due to its high transduction efficiency, pre-existing immunity to Ad5 in many people reduces vaccine efficacy. To address this limitation, simian Ad vectors, such as ChAdOx1 and ChAdOx2, have been explored as alternative vaccine platforms. ChAdOx2 is based on simian Ad25 (SAd25), but the fundamental characteristics of gene transduction by SAd25-based vectors have not been fully elucidated. This study aimed to characterize the gene transduction efficiency, tissue distribution, and immunogenicity of an SAd25-based vector in comparison with those of the Ad5 vector following various routes of administration. Compared with intravenous administration of the Ad5 vector, intravenous administration of the SAd25 vector showed distinct biodistribution patterns, including reduced liver accumulation and predominant expression in the lung. Transduction by the SAd25 vector was not inhibited by human serum, whereas transduction by the Ad5 vector was inhibited, indicating that the SAd25 vector, but not the Ad5 vector, can evade pre-existing Ad immunity. Although intramuscular administration of the SAd25 vector induced lower transgene product-specific antibody production than intramuscular administration of the Ad5 vector, gene expression and Ad genome distribution mediated by the SAd25 vector, but not the Ad5 vector, were localized only to the muscle at the administration site. Intranasal administration of the SAd25 vector induced an antigen-specific antibody response in serum more rapidly than intranasal administration of the Ad5 vector. The SAd25 vector induced antigen-specific antibody production in bronchoalveolar lavage fluid (BALF) that was comparable to that induced by the Ad5 vector. These findings provide essential insights into the biological characteristics of the SAd25 vector, supporting its potential as a safe and effective vaccine vector.

Animals↗
PubMed2026

Genetic diversity and recombination of NA-PRRSV field strains in Vietnam: Implications for vaccine efficacy.

Porcine reproductive and respiratory syndrome (PRRS) causes severe reproductive losses in pregnant sows and piglets, resulting in substantial economic impact on the swine industry worldwide. However, due to the significant genetic diversity and rapid evolutionary changes of the pathogen, continuous surveillance and detailed genetic analysis of circulating strains are essential. The current study aimed to evaluate the genetic diversity of the hypervariable (HV) region of non-structural protein 2 (nsp2) among North American PRRSV strains isolated from swine farms in Vietnam. Phylogenetic analysis and multiple sequence alignment were conducted to determine subtype classification and assess genetic variability. A total of 48 field isolates were obtained, of which 12.5% belonged to classical NA-PRRSV, 16.6% to NADC30-like and 70.9% to HP-PRRSV, primarily distributed across sublineages 1.4, 5.1, 8.7 and 8.9. Amino acid comparisons found multiple insertions, deletions and substitutions at various positions within the hypervariable region of nsp2. The study revealed substantial genetic variation in the HV region of nsp2 among NA-PRRSV field strains, largely associated with recombination and immune escape. These findings highlight epidemiological risks to vaccine efficacy and underscore the need for continuous molecular surveillance to support effective PRRSV control in Vietnam.

PRRSV↗
PubMed1979

Lipopolysaccharide pseudomonas vaccine: efficacy against pulmonary infection with Pseudomonas aeruginosa.

Pneumonia due to Pseudomonas aeruginosa occurs with increased frequency and high mortality in certain populations of patients. The potential of vaccination with a heptavalent lipopolysaccharide pseudomonas vaccine for specific protection of respiratory tissues from infection with Pseudomonas was evaluated with a guinea pig model of experimental pseudomonas pneumonia. Animals routinely responded to vaccination with a fourfold rise in titer of serum hemagglutinating antibody to Pseudomonas. Of 25 control animals, all but nine died after lung challenge with Pseudomonas, whereas vaccinated animals had a greater survival rate (22 of 25 animals survived; P less than 0.01). Rates of clearance of viable Pseudomonas from lung tissue were significantly greater in vaccinated animals than in controls during the first 6 hr after infection. Both gross and microscopic findings of lung tissue damage from pseudomonas pneumonia were less in vaccinated than in control animals. Thus, lipopolysaccharide pseudomonas vaccine appears to produce a local protective response in respiratory tissue against Pseudomonas.

Animals↗
PubMed1979

Epididymitis in rams: studies on vaccine efficacy.

Simultaneous inoculation with Br. ovis bacterin plus Br. abortus strain 19 produced the greatest immunity. This procedure was not permitted, however, as widespread use of Br. abortus in sheep might pose a hazard to the brucellosis eradication program in cattle. Subsequent work demonstrated that an aluminum hydroxide adsorbed bacterin, administered as two injections spaced 3-6 weeks apart, conferred a significant and acceptable level of immunity.

Animals↗
PubMed1979

Evidence of whooping-cough-vaccine efficacy from the 1978 whooping-cough epidemic in Hertfordshire.

The question of the efficacy of whooping-cough immunisation was central to the controversy that started in 1974. Definitive answers were not possible at the time because of the very low levels of whooping-cough in the preceding years and the absence of up-to-date information. The widespread abandonment of whooping-cough immunisation and the subsequent epidemic of whooping-cough have provided a natural epidemiological experiment. Figures from Hertfordshire in 1978 show that for children aged 4 years and under whooping-cough immunisation conferred 92% protection.

Child Health Services↗
PubMed1975

Efficacy of turkey herpesvirus vaccine when administered simultaneously with fowl pox vaccine.

The efficacy of the turkey herpesvirus (HVT) vaccine in protecting chickens challenged with virulent Marek's disease (MD) virus was unaffected by the presence of either the chick embryo fowl pox vaccine or fowl pox vaccine derived from cell culture. Conversely the HVT vaccine did not affect the efficacy of the fowl pox vaccine in chickens challenged with pathogenic fowl pox virus. A combination of spectinomycin dihydrochloride pentahydrate and lincomycin hydrochloride monohydrate as well as spectinomycin sulfate tetrahydrate were found to be compatible with the HVT and fowl pox vaccines as demonstrated by resistance after challenge with virulent MD virus or fowl pox virus.

Animals↗
PubMed1979

Comparison of two infectious bursal disease vaccine strains: efficacy and potential hazards in susceptible and maternally immune birds.

Two infectious bursal disease vaccines were administered to separate groups of maternally immune and susceptible chickens at various ages. Vaccine B caused no damage to the bursae of chickens examined histologically at nine and 20 days after vaccination. The bursae of chickens given vaccine A were shown to be severely damaged when similarly examined. Both vaccines protected all the susceptible groups against challenge, but only vaccine A protected the groups of maternally immune chickens. Susceptible chickens vaccinated at one day of age with vaccine A showed a lowered response to Hitchner B1 Newcastle disease vaccine given at 14 days of age, judged by the haemagglutination-inhibition response and Newcastle disease challenge. The performance of the Newcastle disease vaccine was not affected in chickens given vaccine B. Bedding used by birds given vaccine A was shown to be capable of transmitting vaccinal virus to susceptible chickens, causing severe bursal damage.

Animals↗
PubMed2026

Nitric oxide-assisted lipid nanoparticles amplify mRNA vaccine responses.

mRNA vaccines have made substantial clinical advances, yet their full clinical potential can be further expanded by enhancing cytosolic delivery. Here, we integrate a nitric oxide (NO) generator with lipid nanoparticles (LNPs) to boost mRNA delivery efficiency and mRNA-based vaccine efficacy. SM-102/DEA LNPs, the lead formulation, achieved significantly higher mRNA delivery compared with the FDA approved SM-102 LNPs in both cellular and animal models. The intramuscular administration of SM-102/DEA LNPs encapsulating mRNA encoding SARS-CoV-2 spike protein elicited substantially higher anti-spike IgG levels and robust CD8+ and CD4+ T cell responses compared to SM-102 LNPs. Mechanistic studies revealed that DEA incorporation promotes endosomal escape of mRNA cargos in SM-102/DEA LNPs. These findings establish NO-assisted LNPs as a unique platform for potent mRNA delivery, which provides a new paradigm for overcoming endosomal barriers and improving the efficacy of mRNA vaccines.

COVID-19↗
PubMed1976

Comparison of the humoral and cellular immune response after immunization with live, UV inactivated herpes simplex virus and a subunit vaccine and efficacy of these immunizations.

Antibody and cell-mediated immune responses were measured in rabbits immunized with live, UV inactivated herpes simplex virus or with a subunit vaccine containing envelope proteins. All the types of immunization procedures induced the production of antibody as well as a specific cellular immunity. Furthermore, the subunit vaccine was as effective as the immunization with live or UV inactivated virus to prevent death upon challenge with live HSV. Live HSV induced a transient unresponsiveness of both B and T cells to in vitro stimulation with various mitogens.

Animals↗
PubMed2026

Comparison of immunogenicity, safety, and efficacy of EVA71 vaccine in children: a systematic review and meta-analysis.

INTRODUCTION: Enterovirus 71 (EV-A71) is a principal cause of hand, foot, and mouth disease (HFMD), potentially leading to severe neurological complications in children. Inactivated EV-A71 vaccines have been introduced. This study compares the immunogenicity, safety, and efficacy of EV-A71 vaccines versus placebo in pediatric populations. RESEARCH DESIGN AND METHODS: Following a PROSPERO-registered protocol, RCTs involving EV-A71 in children were identified via PubMed, Scopus, Cochrane, and ClinicalTrials.gov. Two independent reviewers performed screening, extraction, and RoB assessments (RoB 2.0). RESULTS: Five phase III RCTs involving 36,659 children were included. EV-A71 vaccination significantly increased seropositivity across follow-up periods, including early (RR 5.8), medium-term (RR 3.09), and long-term (RR 2.95) response. Seroconversion was significantly higher in the vaccinated group (pooled RR 13.04, 95% CI 2.80-60.61; p&#x2009;<&#x2009;0.001). Geometric mean titers, analyzed using the ratio of means approach, were significantly higher in the vaccinated group during early and medium-term follow-up. Vaccine efficacy against EV-A71-associated HFMD exceeded 98% (pooled RR 0.02, 95% CI 0.01-0.09; p = 0.0028; I2&#x2009;=&#x2009;50%). Solicited local and systemic adverse events were mild and comparable between groups. CONCLUSION: Inactivated EV-A71 vaccines robust immunogenicity, high clinical efficacy, and an acceptable safety profile in children. Future studies should explore long-term protection, booster schedules, and multivalent formulations against non-EV-A71 serotypes.

Humans↗
PubMed1977

Protective efficacy of vaccination in children in four episodes of natural varicella and zoster in the ward.

It was previously reported that a live varicella vaccine (Oka strain) has been developed and that the immediate vaccination of hospitalized children was effective for prevention of spread of varicella in a ward. Six to nine months later, there were four separate episodes of varicella and zoster in the same ward. Eighteen children (11 with nephrotic syndrome, 6 with nephritis, and 1 with hepatitis) with no history of varicella were inoculated with a live vaccine before or immediately after admittance or occurence of the varicella and zoster cases. Twelve of them had been receiving steroid therapy and 15 of the 18 were found to be seronegative by complement fixation and neutralization tests before the vaccination. All of them became seropositive after vaccination without any clinical symptoms. The longest period between vaccination and exposure was nine months. None of the vaccinees exhibited varicella symptoms after exposure. Serological follow-up of ten vaccinated children was done, and booster responses were observed in some of them after exposure. These results suggest that the live vaccine affords immunity to the recipients. If hospitalized children are vaccinated before or immediately after exposure, isolation of the patient is unnecessary.

Adolescent↗
PubMed1979

Measuring the efficacy of vaccination in affording protection against plague.

The relationship of F1 antibody titre to protection against plague was investigated by subjecting seropositive laboratory rats to virulent challenge and observing for survival. The passive haemagglutination (PHA) test in microtitre was employed for serology. Rats vaccinated with live vaccine EV76 (51f), killed U.S.P. vaccine, or F1 antigen and challenged by subcutaneous inoculation of 1 x 10(3) to 5 x 10(5)Yersinia pestis survived at similar rates that, overall, equalled 6% at titres less than 1:16, 46% at titres of 1:32-1:64, 90% at titres of 1:128-1:256, and 96% at titres of 1:512-1:1024. Rats vaccinated with F1 antigen and rats that had been infected previously were challenged intranasally with 8.9 x 10(4)Y. pestis and subsequently demonstrated similar rates of survival that was zero at titres less than 1:128, 86% at titres of 1:128-1:256, and 100% at titres of 1:512-1:1024. The significance of titre of F1 antibody as a measure of seroimmunity against acute bubonic or pneumonic plague is discussed for rats, monkeys, and man.

Animals↗
PubMedDate not supplied

[Rubella vaccines (author's transl)].

After a short report about clinical features of teratogenic effect of rubella virus, the pecularities of several vaccines are reported. Vaccine efficacy and reactions, and rubella vaccine programmes are examined. The immune responses induced by rubella vaccines are described and particularly about the duration of humoral and cellular factors. The AA. discuss about the possibility to use a killed vaccine or a vaccine without teratogenic effect or the experience to give vaccine intranasally.

Antibodies, Viral↗
PubMed2025

Helminth infections affect host immune responses to viral infections and vaccines.

Helminths are highly prevalent in many regions of the world. Due to the chronic nature of most helminth infections, these parasites are proficient immunomodulators of their hosts. This modulation often leads to skewed or even impaired immune responses against unrelated antigens, such as viruses and vaccines, which can be both beneficial and detrimental for the host. The extent of these effects and the impact on the outcomes of viral infection depends on a variety of factors including timing and tropism of both infections, pathological mechanisms, genetic background, and environmental factors. In this review, we dissect these complex interactions between virus and helminths in the context of coinfection and the impact of helminth infection on antiviral vaccine efficacy. We characterize the key contributing mechanisms that have been defined in preclinical models and human trials and describe the immune actors involved in the modulation of the antiviral and vaccine immune response by helminths. Finally, we address the limitations of our current understanding of helminth-virus interactions.

Helminthiasis↗