Browsing by Author "Said, Macarena"
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Publication Factors influencing neutralizing antibody response to the original SARS-CoV-2 virus and the Omicron variant in a high vaccination coverage country, a population-based study(2023) Hormazabal, Juan; Nuñez-Franz, Loreto; Rubilar, Paola; Apablaza, Mauricio; Vial Cox, María Cecilia; Cortes Salinas, Lina Jimena; González, Natalia; Vial, Pablo; Said, Macarena; Gonzalez Wiedmaier, Claudia; Olivares, Kathya; Aguilera, Ximena; Ramírez-Santana, MurielThe study compared immunity to the original SARS-CoV-2 virus (Wuhan) and the Omicron variant using neutralizing antibodies (NAbs), that provide a good approximation of protective immunity. The results might help determine immunization strategies. Design and methods: Unlike previous studies, we analyzed NAbs in a random sample of 110 IgG positive sera from individuals who participated in a population-based seroprevalence transversal study, carried out in May 2022 in two Chilean cities, a country with high vaccination coverage. Results: Our findings indicate that 98.2% of individuals had NAbs against Wuhan, 65.5% against Omicron, and 32.7% tested positive for Wuhan but not Omicron. Factors influencing protective immunity included a prior natural infection and the number of vaccines received. NAbs titers against the original virus were high, demonstrating vaccine effectiveness in the population. However, the level of antibodies decreased when measuring NAbs against Omicron, particularly among older individuals, indicating a decline in vaccine protection. Previous COVID-19 episodes acted as a natural booster, increasing NAbs titers against both virus strains. Conclusions: Protective immunity against the original Wuhan SARS-CoV-2 virus is reduced when compared to Omicron variant. Updating vaccine to target emerging variants and continued monitoring of effectiveness at the population level are necessary.Publication Immunization and SARS-CoV-2 Antibody Seroprevalence in a Country with High Vaccination Coverage: Lessons from Chile(2022) Aguilera, Ximena; González, Claudia; Apablaza, Mauricio; Rubilar, Paola; Icaza, Gloria; Ramírez, Muriel; Pérez, Claudia; Cortes, Lina; Núñez, Loreto; Quezada, Rubén; Castillo, Carla; Correa, Juan; Said, Macarena; Hormazábal, Juan; Vial, Cecilia; Vial, PabloChile 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.Item Immunization and SARS-CoV-2 antibody seroprevalence in a country with high vaccination coverage: Lessons from Chile(2022) Aguilera, Ximena; González, Claudia; Apablaza, Mauricio; Rubilar, Paola; Icaza, Gloria; Ramírez-Santana, Muriel; Pérez, Claudia; Cortés, Lina Jimena; Núñez-Franz, Loreto; Quezada-Gaete, Rubén; Castillo-Laborde, Carla; Correa, Juan; Said, Macarena; Hormazábal, Juan; Vial, Cecilia; Vial, PabloObjective: Chile is among the most successful nations worldwide in COVID-19 vaccine rollout. By December 31st, 2021, 84.1% of the population was fully vaccinated, and 56.1% received booster doses using DIFFERENT TYPES OF COVID-19 VACCINES. In this context, we aimed to estimate the anti-SARSCoV-2 antibodies following the infection and vaccination campaign. Study design: Population-based cross-sectional serosurvey based on a representative sample of the cities of Santiago, Coquimbo/La Serena, and Talca used in a previous study. Methods: We selected the participants using a three-stage stratified sampling. They were blood-sampled on-site and answered a questionnaire regarding COVID-19-associated variables and vaccination antecedents using Wantai SARS-CoV-2 Ab ELISA to determine seroprevalence. This research followed the generic protocol of World Health Organization Unity studies. Results: We recruited 2,198 individuals aged 7-93 between October 5th and November 25th, 2021. In our sample, 2,132 individuals received COVID-19 vaccinations (97%); 67 (3.1%) received one dose; 2,065 (93.9%) received the complete scheme; 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. Conclusion: We found a seroprevalence close to 100% in the population aged seven years and older, primarily due to the successful vaccination program, which has a strong emphasis on universal access.Item SARS-CoV-2 Neutralizing Antibodies in Chile after a Vaccination Campaign with Five Different Schemes(2022) Aguilera, Ximena; Hormazábal, Juan; Vial, Cecilia; Cortés, Lina Jimena; González, Claudia; Rubilar, Paola; Apablaza, Mauricio; Ramírez-Santana, Muriel; Icaza, Gloria; Núñez-Franz, Loreto; Castillo-Laborde, Carla; Ramírez-Riffo, Carolina; Pérez, Claudia; Quezada-Gate, Rubén; Said, Macarena; Vial, PabloUsing 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.Item Seroprevalence of Natural and Acquired Immunity against the SARS-CoV-2 Virus in a Population Cohort from Two Chilean Cities, 2020–2022(2023) Núñez-Franz, Loreto; Ramírez-Santana, Muriel; Rubilar, Paola; Vial, Cecilia; Apablaza, Mauricio; González, Claudia; Said, Macarena; Olivares, Kathya; Cortés, Lina Jimena; Hormazábal, Juan; Canales, Luis; Vial, Pablo; Icaza, Gloria; Quezada-Gaete, Rubén; Aguilera, XimenaBackground: 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.