Publications by authors named "Xavier Saez-Llorens"

Background: Nirsevimab is an extended half-life, highly potent neutralizing monoclonal antibody against the respiratory syncytial virus (RSV) fusion protein, with efficacy in preventing RSV-associated medically attended (MA) lower respiratory tract infection (LRTI) in infants and medically vulnerable children (aged ≤24 months). This post-hoc exploratory analysis examined the incidence of LRTI from RSV and other respiratory pathogens during a 2:1 randomized, double-blind, placebo-controlled, phase 3 study of nirsevimab, in healthy-term and late-preterm (i.e.

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As robust cellular responses are important for protection against dengue, this phase 2 study evaluated the kinetics and phenotype of T cell responses induced by TAK-003, a live-attenuated tetravalent dengue vaccine, in 4-16-year-old living in dengue-endemic countries (NCT02948829). Two hundred participants received TAK-003 on Days 1 and 90. Interferon-gamma (IFN-γ) enzyme-linked immunospot assay [ELISPOT] and intracellular cytokine staining were used to analyze T cell response and functionality, using peptide pools representing non-structural (NS) proteins NS3 and NS5 matching DENV-1, -2, -3, and -4 and DENV-2 NS1.

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Introduction: Dengue disease represents a large and growing global threat to public health, accounting for a significant burden to health systems of endemic countries. The World Health Organization's (WHO) Strategic Advisory Group of Experts (SAGE) and the European Medicines Agency (EMA) currently recommend the use of TAK-003 dengue vaccine in high dengue burden and transmission settings for countries considering vaccination as part of their integrated management strategy for prevention and control of Dengue.

Areas Covered: This paper describes the main conclusions of a workshop held by the Arbovirus Committee of the Latin American Society of Pediatric Infectious Diseases (SLIPE) in November 2023, to generate consensus recommendations on the introduction of this new vaccine in the region.

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Article Synopsis
  • RSV is the top cause of severe respiratory infections in children and has seen a rise in cases post-pandemic, especially in low- and middle-income countries.
  • Traditional treatments have been mainly supportive, but new preventive measures like long-acting monoclonal antibodies and vaccinations for pregnant women are becoming available.
  • The Latin American Pediatric Infectious Diseases Society (SLIPE) is assessing the impact of RSV in the LAC region and recommending new strategies for prevention.
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Background: Dengue is an increasing threat to global health. This exploratory analysis evaluated the immunogenicity, safety, and vaccine efficacy (VE) of a live-attenuated tetravalent dengue vaccine (TAK-003) in participants enrolled in the phase 3 DEN-301 trial (NCT02747927), stratified by baseline age (4-5 years; 6-11 years; or 12-16 years).

Methods: Participants were randomized 2:1 to receive 2 doses of TAK-003, administered 3 months apart, or placebo.

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Article Synopsis
  • The study investigated how previous vaccinations for Yellow Fever (YF) and Japanese Encephalitis (JE) affect the effectiveness of the dengue vaccine candidate, TAK-003, in children aged 4-16 years.
  • Out of 20,071 participants, different levels of vaccine efficacy were observed: 55.7% in those previously vaccinated for YF, 77.8% for JE, and 53.5% for those with no prior vaccinations, but these results were influenced by the regional distribution of dengue virus serotypes.
  • Overall, the findings indicate that prior YF or JE vaccinations do not significantly impact the efficacy of TAK-003, which was well-tolerated across various epidemiological settings.
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  • - Norovirus is a leading cause of acute gastroenteritis (AGE), and the study aimed to gather data on its prevalence and impact in Panama while following COVID-19 safety protocols.
  • - The research involved monitoring children under two years old through community and hospital-based surveillance, with 400 participants contributing data over several months from January to September 2020, despite interruptions due to the pandemic.
  • - The results indicated a total of 185 AGE cases in the longitudinal study, with a specific incidence of norovirus-related cases being relatively low (0.3 episodes per 100 child-months), highlighting the need for ongoing research and effective preventive measures.
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  • About half of the global population lives in areas where dengue fever is common, leading researchers to test the tetravalent dengue vaccine TAK-003 for its long-term effectiveness in children and adolescents aged 4-16.
  • The study is a double-blind, placebo-controlled trial conducted across eight dengue-endemic countries, enrolling over 20,000 participants, and focusing on the vaccine's ability to prevent symptomatic dengue disease.
  • Results will be evaluated over approximately 4.5 years, monitoring both efficacy and the incidence of serious adverse events, with ongoing oversight to ensure participant safety.
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  • The first 1,000 days of life are vital for child development, but there's a lack of information on influencing factors in the Latin America and the Caribbean (LAC) region.
  • In May 2022, the Latin American Pediatric Infectious Diseases Society (SLIPE) organized a workshop with experts to discuss key issues affecting childhood development and maternal infant health in LAC.
  • The goal was to identify priorities and create actionable recommendations to improve maternal and infant care, focusing on reducing mortality from infections and preventable diseases during this critical developmental period.
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  • The review focuses on toxoplasmosis rates in Panama and Colombia, analyzing data on seroprevalence and risk factors.
  • Studies showed seroprevalence in Ciudad de Panamá ranged from 22% to 44%, with higher rates linked to poverty and closeness to water.
  • Heat maps and mathematical models were created to pinpoint areas that need targeted healthcare campaigns for congenital toxoplasmosis and infections.
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  • A study was conducted to evaluate the safety and immune response of a new RSV vaccine (ChAd155-RSV) in infants aged 6-7 months, comparing different doses and an active comparator.* -
  • The trial involved 201 infants, with results indicating that the vaccine had a safety profile comparable to existing childhood vaccines, and did not lead to adverse respiratory effects associated with RSV infections.* -
  • Higher doses of the ChAd155-RSV vaccine produced stronger immune responses, with increased antibody levels observed after vaccination, especially following the second dose.*
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  • - The study involved a dose-finding trial for the HilleVax bivalent vaccine (HIL-214) in children aged 6 months to 4 years across Panama and Colombia, with 120 participants per age cohort.
  • - Participants were divided into four groups receiving different vaccine formulations, and responses to the vaccine were measured at multiple intervals, showing significant antibody responses particularly after the second dose, especially in the younger cohort.
  • - The vaccine was well-tolerated with mild side effects reported, and the antibody levels remained elevated for at least 210 days post-vaccination, indicating potential for further development to protect young children from norovirus.
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  • The purpose of the review was to develop and assess educational materials aimed at reducing disease burdens from infections in Panama, Colombia, and the USA.
  • Recent findings indicate that educational programs in these countries have not yet been evaluated for their effectiveness, despite being implemented for various demographics like high school students and pregnant women.
  • The summary highlights that these educational materials have shown short-term benefits in disseminating information, with future goals focusing on conducting long-term studies, updating materials based on new research, and increasing access to these resources for broader public health impact.
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In the pivotal phase 3 efficacy trial (NCT02747927) of the TAK-003 dengue vaccine, 5 of 13,380 TAK-003 recipients and 13 of 6,687 placebo recipients experienced two episodes of symptomatic dengue between the first dose and the end of the study, ∼57 months later (patients received the second dose 3 months after the first dose). Two of these participants experienced repeat infection with the same serotype (i.e.

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Background: Safe and effective respiratory syncytial virus (RSV) vaccines remain elusive. This was a phase I/II trial (NCT02927873) of ChAd155-RSV, an investigational chimpanzee adenovirus-RSV vaccine expressing 3 proteins (fusion, nucleoprotein, and M2-1), administered to 12-23-month-old RSV-seropositive children followed up for 2 years after vaccination.

Methods: Children were randomized to receive 2 doses of ChAd155-RSV or placebo (at a 1:1 ratio) (days 1 and 31).

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  • Sabin strains in oral poliovirus vaccines (OPV) can revert to harmful forms, prompting the development of a new OPV2 (nOPV2) designed to remain stable and reduce disease-causing strains in populations with low vaccination rates.
  • In clinical trials conducted in Panama, infants received either monovalent OPV2 (mOPV2) or nOPV2, and researchers analyzed the poliovirus shed in their stools for genetic and phenotypic changes post-vaccination.
  • Results indicated that the Sabin-2 strain rapidly reverts to virulent forms, but nOPV2 showed little to no increase in neurovirulence, indicating it may be a safer option with significantly lower paralysis rates
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This review summarizes the recent Global Meningococcal Initiative (GMI) regional meeting, which explored meningococcal disease in North America. Invasive meningococcal disease (IMD) cases are documented through both passive and active surveillance networks. IMD appears to be decreasing in many areas, such as the Dominican Republic (2016: 18 cases; 2021: 2 cases) and Panama (2008: 1 case/100,000; 2021: <0.

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Background: To meet the demand for effective and affordable inactivated polio vaccines (IPVs), a reduced dose, aluminium hydroxide (Al(OH))-adjuvanted IPV vaccine was developed (IPV-Al, Picovax®) and evaluated in clinical trials. The present trial is an extension of two previous trials (a primary and a booster trial). The aim was to evaluate the persistence of seroprotective antibodies (poliovirus type-specific antibody titre ≥ 8) in 4-year-old children who previously received IPV-Al as primary and booster vaccine doses and to determine the potential booster response and safety profile of an additional dose of IPV-Al.

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Purpose Of Review: Review building of programs to eliminate infections.

Recent Findings: Morbidity and mortality from toxoplasmosis led to programs in USA, Panama, and Colombia to facilitate understanding, treatment, prevention, and regional resources, incorporating student work.

Summary: Studies foundational for building recent, regional approaches/programs are reviewed.

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Article Synopsis
  • The review discusses international efforts to create a global public health initiative for toxoplasmosis, aiming to enhance maternal and child health by preventing and treating the disease.
  • Recent findings indicate that some countries are making progress in eliminating toxoplasmosis but face significant challenges.
  • Key issues include the high costs and inaccessibility of diagnostic tests and treatment, especially for marginalized communities, as well as delays in essential medical procedures and insurance processes.
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Background: The COVID-19 vaccine candidate CVnCoV comprises sequence-optimized mRNA encoding SARS-CoV-2 S-protein encapsulated in lipid nanoparticles. In this phase 2a study, we assessed reactogenicity and immunogenicity of two or three doses in younger and older adults.

Methods: Younger (18-60 years) and older (>60 years) adults were enrolled in two sites in Panama and Peru to receive either 6 or 12 µg doses of CVnCoV or licensed control vaccines 28 days apart; subsets received a 12 µg booster dose on Day 57 or Day 180.

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  • Young children can experience significant health issues from norovirus gastroenteritis, prompting a study on the TAK-214 bivalent vaccine in kids aged 1-8 years.
  • The phase 2 study involved 120 children from Finland, Panama, and Colombia who received different formulations of the vaccine, with results showing it was well-tolerated and led to strong immune responses.
  • After two doses, the vaccine induced durable immunity against norovirus with high seroresponse rates, confirming that TAK-214 is a promising candidate for preventing this illness in young children.
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Novel oral poliovirus vaccine type 2 (nOPV2) is being developed to reduce the rare occurrence of disease and outbreaks associated with the genetic instability of the Sabin vaccine strains. Children aged 1 to 5 years were enrolled in two related clinical studies to assess safety, immunogenicity, shedding rates and properties of the shed virus following vaccination with nOPV2 (two candidates) versus traditional Sabin OPV type 2 (mOPV2). The anticipated pattern of reversion and increased virulence was observed for shed Sabin-2 virus, as assessed using a mouse model of poliovirus neurovirulence.

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