Browsing by Author "Abarca, K."

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    An inactivated SARS-CoV-2 vaccine is safe and induces humoral and cellular immunity against virus variants in healthy children and adolescents in Chile
    (2022) Soto, J.A.; Melo-González, F.; Gutierrez-Vera, C.; Schultz, B.M.; Berríos-Rojas, R.V.; Rivera-Pérez, D.; Piña-Iturbe, A.; Hoppe-Elsholz, G.; Duarte, L.F.; Vázquez, Y.; Moreno-Tapia, D.; Ríos, M.; Palacios, P.A.; Garcia-Betancourt, R.; Santibañez, Á.; Mendez, C.; Diethelm-Varela, B.; Astudillo, P.; Calvo, M.; Cárdenas, A.; González, M.; Goldsack, M.; Gutiérrez, V.; Potin, M.; Schilling, A.; Tapia, L.I.; Twele, L.; Villena, R.; Grifoni, A.; Sette, A.; Weiskopf, D.; Fasce, R.A.; Fernández, J.; Mora, J.; Ramírez, E.; Gaete-Argel, A.; Acevedo, M.; Valiente-Echeverría, F.; Soto-Rifo, R.; Retamal-Díaz, A.; Muñoz-Jofré, N.; Meng, X.; Xin, Q.; Alarcón-Bustamante, E.; González-Aramundiz, J.V.; Le Corre, N.; Álvarez, M.J.; González, P.A.; Abarca, K.; Perret, C.; Carreño, L.J.; Kalergis, A.M.; Bueno, S.M.
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    Flea and ticks species from dogs in urban and rural areas in four districts in Chile
    (2016) Abarca, K.; Garate, D.; Lopez, J.; Acosta-Jamett, G.
    Fleas and ticks frequently parasitise canines worldwide and their prevalence in dogs is influenced by many factors including climate and geography, among others. Different studies worldwide have shown no clear pattern of an urban or rural preference by different species of fleas and ticks infesting dogs. The aim of this study is to identify species of fleas and ticks present in urban and rural dogs from different ecoregions of Chile. A cross-sectional study was conducted in four urban-rural paired sites at four districts: Arica y Parinacota, Coquimbo, Metropolitana and Araucania. A random and a convenience sampling of households in the urban and rural areas was carried out, collecting fleas and ticks from 112-114 dogs per locality. The frequency of fleas and ticks infestation between urban and rural areas was compared through Chi-square or Fisher's tests. A total of 921 dogs were examined, identifying four species of fleas (Ctenocephalides canis, Ctenocephalides felis, Pulex irritans and Echidnophaga gallinacea) and three species of ticks (Rhipicephalus sanguineus, Amblyomma tigrinunz and Amblyomma triste). In general, a higher prevalence of dogs with fleas were observed in rural areas, being C. canis the most frequent species globally; there were significant variations in the distribution of different species according to district. R. sanguineus was the predominant tick in all the studied areas. Amblyomma species were found exclusively in rural areas; A. triste only in Arica y Parinacota and A. tigrinum in rural areas of Coquimbo and Araucania districts.
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    Humoral and cellular response induced by a second booster of an inactivated SARS-CoV-2 vaccine in adults
    (2022) Melo González, Felipe; Méndez, Constanza; Peñaloza, H.F.; Schultz, B.M.; Piña Iturbe, A.; Ríos, M.; Moreno Tapia, D.; Pereira Sánchez, P.; Leighton, D.; Orellana, C.; Covarrubias, C.; Gálvez, N.M.S.; Soto, J.A.; Duarte, L.F.; Rivera Pérez, D.; Vázquez, Y.; Cabrera, A.; Bustos, S.; Iturriaga, C.; Urzua, M.; Navarrete, M.S.; Rojas, Á.; Fasce, R.; Fernández, J.; Mora, J.; Ramírez, E.; Gaete Argel, A.; Acevedo, M.; Valiente Echeverría, F.; Soto Rifo, R.; Weiskopf, D.; Grifoni, A.; Sette, A.; Zeng, G.; Meng, W.; González Aramundiz, J.V.; González, P.A.; Abarca, K.; Bueno, S.M.; Kalergis, A.M.
    The SARS-CoV-2 Omicron variant has challenged the control of the COVID-19 pandemic even in highly vaccinated countries. While a second booster of mRNA vaccines improved the immunity against SARS-CoV-2, the humoral and cellular responses induced by a second booster of an inactivated SARS-CoV-2 vaccine have not been studied. In the context of a phase 3 clinical study, we report that a second booster of CoronaVac® increased the neutralizing response against the ancestral virus yet showed poor neutralization against the Omicron variant. Additionally, isolated PBMCs displayed equivalent activation of specific CD4+ T cells and IFN-γ production when stimulated with a mega-pool of peptides derived from the spike protein of the ancestral virus or the Omicron variant. In conclusion, a second booster dose of CoronaVac® does not improve the neutralizing response against the Omicron variant compared with the first booster dose, yet it helps maintaining a robust spike-specific CD4+ T cell response.
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    Immunogenicity, safety, and interchangeability of two inactivated hepatitis A vaccines in Chilean children
    (2008) Abarca, K.; Ibánez, I.; Perret Pérez, Cecilia; Vial, P.; Zinsou, J. A.
    Objectives: To compare the immunogenicity, safety, and interchangeability of two pediatric hepatitis A vaccines, Avaxim 80U-Pediatric® and Havrix 720®, in Chilean children. Methods: In this randomized trial, 332 hepatitis A virus (HAV) seronegative children from 1 to 15 years of age received two doses of Avaxim, two doses of Havrix, or Havrix followed by Avaxim, 6 months apart. Anti-HAV antibody titers were measured before and 14 days after the first dose of vaccine, and before and 28 days after the second dose of vaccine. Immediate reactions were monitored; reactogenicity was evaluated from parental reports. Results: Seroconversion rates after the first vaccination were 99.4% and 100% for Avaxim and Havrix, respectively. Anti-HAV geometric mean concentrations (GMCs) were 138 mIU/ml for Havrix (95% confidence interval (CI): 120; 159) and 311 mIU/ml for Avaxim (95% CI: 274; 353). GMCs increased to 4008 mIU/ml after two doses of Havrix, 8537 mIU/ml following two doses of Avaxim, and 7144 mIU/ml in children who received Havrix with Avaxim as the second dose. Following the first injection, 36% of subjects given Avaxim and 44% given Havrix reported local reactions; 38% of subjects in the Avaxim group and 40% in the Havrix group reported systemic reactions related to vaccination. Solicited reactions were less frequent after the second dose of Avaxim or Havrix, occurring in 27% to 37% of subjects. Conclusions: No significant difference in seroconversion rates was seen 14 days after a single dose of vaccine. A two-dose schedule with either vaccine or with Havrix/Avaxim provided a strong booster response. Both vaccines were well tolerated and can be recommended for routine vaccination of Chilean children. Avaxim 80 may be used to complete a vaccine schedule begun with Havrix 720. © 2007 International Society for Infectious Diseases.
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    Inactivated Vaccine-Induced SARS-CoV-2 Variant-Specific Immunity in Children
    (2022) Soto, J.A.; Melo-González, F.; Gutierrez-Vera, C.; Schultz, B.M.; Berríos-Rojas, R.V.; Rivera-Pérez, D.; Piña-Iturbe, A.; Hoppe-Elsholz, G.; Duarte, L.F.; Vázquez, Y.; Moreno-Tapia, D.; Ríos, M.; Palacios, P.A.; Garcia-Betancourt, R.; Santibañez, Á.; Pacheco, G.A.; Mendez, C.; Andrade, C.A.; Silva, P.H.; Diethelm-Varela, B.; Astudillo, P.; Calvo, M.; Cárdenas, A.; González, M.; Goldsack, M.; Gutiérrez, V.; Potin, M.; Schilling, A.; Tapia, L.I.; Twele, L.; Villena, R.; Grifoni, A.; Sette, A.; Weiskopf, D.; Fasce, R.A.; Fernández, J.; Mora, J.; Ramírez, E.; Gaete-Argel, A.; Acevedo, M.L.; Valiente-Echeverría, F.; Soto-Rifo, R.; Retamal-Díaz, A.; Muñoz-Jofré, N.; Meng, X.; Xin, Q.; Alarcón-Bustamante, E.; González-Aramundiz, J.V.; Le Corre, N.; Álvarez-Figueroa, M.J.; González, P.A.; Abarca, K.; Perret, C.; Carreño, L.J.; Bueno, S.M.; Kalergis, A.M.
    Multiple vaccines against severe acute respiratory syndrome coronavirus 2 (SARS-CoV-2) have been evaluated in clinical trials. However, trials addressing the immune response in the pediatric population are scarce. The inactivated vaccine CoronaVac has been shown to be safe and immunogenic in a phase 1/2 clinical trial in a pediatric cohort in China. Here, we report interim safety and immunogenicity results of a phase 3 clinical trial for CoronaVac in healthy children and adolescents in Chile. Participants 3 to 17 years old received two doses of CoronaVac in a 4-week interval until 31 December 2021. Local and systemic adverse reactions were registered for volunteers who received one or two doses of CoronaVac. Whole-blood samples were collected from a subgroup of 148 participants for humoral and cellular immunity analyses. The main adverse reaction reported after the first and second doses was pain at the injection site. Four weeks after the second dose, an increase in neutralizing antibody titer was observed in subjects relative to their baseline visit. Similar results were found for activation of specific CD4+ T cells. Neutralizing antibodies were identified against the Delta and Omicron variants. However, these titers were lower than those for the D614G strain. Importantly, comparable CD4+ T cell responses were detected against these variants of concern. Therefore, CoronaVac is safe and immunogenic in subjects 3 to 17 years old, inducing neutralizing antibody secretion and activating CD4+ T cells against SARS-CoV-2 and its variants. (This study has been registered at ClinicalTrials.gov under no. NCT04992260.) IMPORTANCE This work evaluated the immune response induced by two doses of CoronaVac separated by 4 weeks in healthy children and adolescents in Chile. To date, few studies have described the effects of CoronaVac in the pediatric population. Therefore, it is essential to generate knowledge regarding the protection of vaccines in this population. Along these lines, we reported the anti-S humoral response and cellular immune response to several SARS-CoV-2 proteins that have been published and recently studied. Here, we show that a vaccination schedule consisting of two doses separated by 4 weeks induces the secretion of neutralizing antibodies against SARS-CoV-2. Furthermore, CoronaVac induces the activation of CD4+ T cells upon stimulation with peptides from the proteome of SARS-CoV-2. These results indicate that, even though the neutralizing antibody response induced by vaccination decreases against the Delta and Omicron variants, the cellular response against these variants is comparable to the response against the ancestral strain D614G, even being significantly higher against Omicron.
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    Yellow fever vaccination for chilean tourists visiting Brazil. Practical considerations
    (2018) Weitzel, T.; Perret, C.; Valdivieso, F.; Abarca, K.; Vial, P.
    Due to the recent yellow fever outbreak affecting the costal region of Brazil, including main touristic destinations, there is a high demand of yellow fever vaccination. This publication addresses the most relevant practical issues regarding this vaccine for tourists visiting Brazil and aims to serve as a guideline for non-expert physicians in Chile and elsewhere.