APABLAZA SALINAS, MAURICIO IVÁN
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APABLAZA SALINAS, MAURICIO IVÁN
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mapablaza@udd.cl
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56845856600

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First wave of SARS-CoV-2 in Santiago Chile: Seroprevalence, asymptomatic infection and infection fatality rate

2022 , VIAL CLARO, PABLO AGUSTIN , GONZALEZ WIEDMAIER, CLAUDIA MARTA , APABLAZA SALINAS, MAURICIO IVÁN , VIAL COX, MARIA CECILIA , Gloria Icaza , ARAOS BRALIC, RAFAEL IGNACIO , RUBILAR RAMIREZ, PAOLA , Juan Correa , Andrei Florea , PEREZ ACUÑA, CLAUDIA VERONICA , Paula Concha , Diego Bastías , María Paz Errázuriz , Ruth Pérez , M.Estela Lavín , OLEA NORMANDIN, ANDREA MARIA , MUNITA SEPULVEDA, JOSE MANUEL , AGUILERA SANHUEZA, XIMENA PAZ , Francisco Guzmán , Eugenio Guzmán

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SARS-CoV-2 Neutralizing Antibodies in Chile after a Vaccination Campaign with Five Different Schemes

2022 , AGUILERA SANHUEZA, XIMENA PAZ , HORMAZABAL CASTILLO, JUAN PATRICIO , VIAL COX, MARIA CECILIA , CORTES SALINAS, LINA JIMENA , GONZALEZ WIEDMAIER, CLAUDIA MARTA , RUBILAR RAMIREZ, PAOLA , APABLAZA SALINAS, MAURICIO IVÁN , Muriel Ramírez-Santana , Gloria Icaza , Loreto Nuñez-Franz , Rubén Quezada-Gate , Macarena Said , PEREZ ACUÑA, CLAUDIA VERONICA , CASTILLO LABORDE, CARLA CECILIA , Carolina Sacristán Ramírez , VIAL CLARO, PABLO AGUSTIN

Using levels of neutralizing antibodies (nAbs), we evaluate the successful Chilean SARS-CoV-2 vaccine campaign, which combines different vaccine technologies and heterologous boosters. From a population-based study performed in November 2021, we randomly selected 120 seropositive individuals, organized into six groups of positive samples (20 subjects each) according to natural infection history and the five most frequent vaccination schemes. We conclude that the booster dose, regardless of vaccine technology or natural infection, and mRNA vaccines significantly improve nAbs response.

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Seroprevalence, spatial distribution, and social determinants of SARS-CoV-2 in three urban centers of Chile

2022 , VIAL CLARO, PABLO AGUSTIN , GONZALEZ WIEDMAIER, CLAUDIA MARTA , Gloria Icaza , Muriel Ramirez-Santana , Rubén Quezada-Gaete , Loreto Núñez-Franz , VIAL COX, MARIA CECILIA , APABLAZA SALINAS, MAURICIO IVÁN , RUBILAR RAMIREZ, PAOLA , Juan Correa , PEREZ ACUÑA, CLAUDIA VERONICA , Andrei Florea , Eugenio Guzmán , María-Estela Lavín , Paula Concha , Manuel Nájera , AGUILERA SANHUEZA, XIMENA PAZ

Abstract Background Seroprevalence studies provide an accurate measure of SARS-CoV-2 spread and the presence of asymptomatic cases. They also provide information on the uneven impact of the pandemic, pointing out vulnerable groups to prioritize which is particularly relevant in unequal societies. However, due to their high cost, they provide limited evidence of spatial spread of the pandemic specially in unequal societies. Our objective was to estimate the prevalence of SARS-CoV-2 antibodies in Chile and model its spatial risk distribution. Methods During Oct–Nov 2020, we conducted a population-based serosurvey in Santiago, Talca, and Coquimbo–La Serena (2493 individuals). We explored the individual association between positive results and socio-economic and health-related variables by logistic regression for complex surveys. Then, using an Empirical Bayesian Kriging model, we estimated the infection risk spatial distribution using individual and census information, and compared these results with official records. Results Seroprevalence was 10.4% (95% CI 7.8–13.7%), ranging from 2% (Talca) to 11% (Santiago), almost three times the number officially reported. Approximately 36% of these were asymptomatic, reaching 82% below 15 years old. Seroprevalence was associated with the city of residence, previous COVID-19 diagnosis, contact with confirmed cases (especially at household), and foreign nationality. The spatial model accurately interpolated the distribution of disease risk within the cities finding significant differences in the predicted probabilities of SARS-CoV-2 infection by census zone (IQR 2.5–15.0%), related to population density and education. Conclusions Our results underscore the transmission heterogeneity of SARS-CoV-2 within and across three urban centers of Chile. Socio-economic factors and the outcomes of this seroprevalence study enable us to identify priority areas for intervention. Our methodological approach and results can help guide the design of interdisciplinary strategies for urban contexts, not only for SARS-CoV-2 but also for other communicable diseases.

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Immunization and SARS-CoV-2 Antibody Seroprevalence in a Country with High Vaccination Coverage: Lessons from Chile

2022 , AGUILERA SANHUEZA, XIMENA PAZ , Gloria Icaza , GONZALEZ WIEDMAIER, CLAUDIA MARTA , RUBILAR RAMIREZ, PAOLA , APABLAZA SALINAS, MAURICIO IVÁN , Muriel Ramírez-Santana , PEREZ ACUÑA, CLAUDIA VERONICA , CORTES SALINAS, LINA JIMENA , Loreto Núñez-Franz , Rubén Quezada-Gaete , CASTILLO LABORDE, CARLA CECILIA , Juan Correa , Macarena Said , HORMAZABAL CASTILLO, JUAN PATRICIO , VIAL COX, MARIA CECILIA , VIAL CLARO, PABLO AGUSTIN

Chile is among the most successful nations worldwide in terms of its COVID-19 vaccine rollout. By 31 December 2021, 84.1% of the population was fully vaccinated, and 56.1% received booster doses using different COVID-19 vaccines. In this context, we aimed to estimate the prevalence of anti-SARS-CoV-2 antibodies following the infection and vaccination campaign. Using a three-stage stratified sampling, we performed a population-based cross-sectional serosurvey based on a representative sample of three Chilean cities. Selected participants were blood-sampled on-site and answered a short COVID-19 and vaccination history questionnaire using Wantai SARS-CoV-2 Ab ELISA to determine seroprevalence. We recruited 2198 individuals aged 7–93 between 5 October and 25 November 2021; 2132 individuals received COVID-19 vaccinations (97%), 67 (3.1%) received one dose, 2065 (93.9%) received two doses, and 936 received the booster jab (42.6%). Antibody seroprevalence reached 97.3%, ranging from 40.9% among those not vaccinated to 99.8% in those with booster doses (OR = 674.6, 154.8–2938.5). SARS-CoV-2 antibodies were associated with vaccination, previous COVID-19 diagnosis, age group, and city of residence. In contrast, we found no significant differences in the type of vaccine used, education, nationality, or type of health insurance. We found a seroprevalence close to 100%, primarily due to the successful vaccination program, which strongly emphasizes universal access.

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Under five and infant mortality in Chile (1990-2016): Trends, disparities, and causes of death

2020 , AGUILERA SANHUEZA, XIMENA PAZ , Gloria Icaza , DELGADO BECERRA, OROZIMBA IRIS , Loreto Villanueva , APABLAZA SALINAS, MAURICIO IVÁN , CASTILLO LABORDE, CARLA CECILIA , Hajo Zeeb

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Seroprevalence of Natural and Acquired Immunity against the SARS-CoV-2 Virus in a Population Cohort from Two Chilean Cities, 2020–2022

2023 , Loreto Núñez-Franz , Muriel Ramírez-Santana , RUBILAR RAMIREZ, PAOLA , Macarena Said , VIAL COX, MARIA CECILIA , Luis Canales , GONZALEZ WIEDMAIER, CLAUDIA MARTA , APABLAZA SALINAS, MAURICIO IVÁN , Gloria Icaza , HORMAZABAL CASTILLO, JUAN PATRICIO , Rubén Quezada-Gaete , VIAL CLARO, PABLO AGUSTIN , Kathya Olivares , CORTES SALINAS, LINA JIMENA , AGUILERA SANHUEZA, XIMENA PAZ

Background: Chile has achieved the highest coverage for vaccines against the SARS-CoV-2 virus worldwide. Objective: To assess the progression of immunity (natural and acquired by vaccine) in a cohort from two Chilean cities. Methods: Individuals (n = 386) who participated in three phases of population-based serial prevalence studies were included (2020–2021 and 2022). Presence of SARS-CoV-2 antibodies was measured in serum. Data including time of vaccination and type of vaccine received were analysed with descriptive statistics. Results: Seroprevalence was 3.6% in the first round and increased to 96.9% in the second and 98.7% in the third. In the third round, 75% of individuals who had received the basal full scheme were seropositive at 180 days or more since their last dose; 98% of individuals who received one booster dose were seropositive at 180 days or more, and 100% participants who received two boosters were seropositive, regardless of time since their last dose. Participants receiving mRNA vaccines had higher seroprevalence rates over time. Conclusions: The high vaccination coverage in Chile enabled the population to maintain high levels of antibodies. Vaccination boosters are essential to maintain immunity over time, which also depends on the type of vaccine administered.

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