Browsing by Author "Nuñez-Franz, Loreto"
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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; Cortés Salinas, Lina Jimena; González, Natalia; Vial, Pablo; Said, Macarena; González 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 Population-based seroprevalence survey: post-pandemic COVID-19 vaccination, related factors, and geographic distribution of vaccine acceptability in Chile(2025) Nuñez-Franz, Loreto; Rubilar, Paola; Apablaza, Mauricio; Canales, Luis; Cortés, Lina J.; Molina, Xaviera; Said, Macarena; Olivares, Kathya; Correa, Juan; Ramírez-Santana, MurielBackground Prevention of infectious diseases is based on host protection, especially using vaccines. Several factors have been linked to the acceptance of vaccines in the population. Chile achieved high COVID-19 vaccination coverage early in the pandemic. The study aimed to determine the prevalence of antigens and antibodies, vaccination status, geographical distribution, and factors related to vaccine acceptability. Methods In two Chilean cities, the fourth round of a population-based seroprevalence cross-sectional survey was conducted in May 2024. 654 participants aged seven or older were recruited. After signing consent, participants were interviewed, blood samples were taken to identify antibodies against SARS-CoV-2 using ELISA, and antigens were assessed through a nasal swab rapid test. Territorial analysis of the vaccine dose distribution was carried out. Results All participants tested negative for antigens and positive for antibodies against SARS-CoV-2, with an overall vaccination uptake rate of 98,5%. However, their vaccination status was heterogeneous. Territorial distribution showed a slight geographical clustering of vaccine doses in both cities. 52.7% had the basic scheme and/or boosters, 32.1% had the bivalent vaccine, and 13.7% had anti-Omicron. Self-report identification with a risk group was not associated with vaccine adherence. City, age, education, and comorbidities were associated with perceived and actual risk discrepancies. Conclusions Overall, vaccine acceptance is high. However, the acceptance of the last two doses was below expectations and showed heterogeneous geographical distribution. Adulthood is the most important predictor of vaccine uptake. Participants underestimated their level of risk. Risk communication must be improved, especially for risk groups, to help them perceive themselves as beneficiaries of vaccination. Efforts should be made to disseminate information on vaccine safety and counter misinformation to increase knowledge about vaccines.