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Introducción: La evaluación clínica de vacunas anti-COVID-19 en edades pediátricas, es un desafío en tiempos de pandemia; responde a la urgencia de muestras representativas que contribuyan a la reproducibilidad del estudio en la población real. Objetivo: Caracterizar a los adolescentes participantes del ensayo clínico con la vacuna anti-COVID-19 Abdala, evaluar el cumplimiento del esquema de vacunación y estimar si son representativos de este grupo poblacional. Métodos: Se utilizaron los datos de un ensayo fase II, monocéntrico, no controlado con la vacuna Abdala. Se incluyeron 703 sujetos; 207 (29,4 por ciento) fueron adolescentes de entre 12 y 18 años, aparentemente sanos o con enfermedades crónicas controladas, valoración nutricional entre 10 y 90 percentil y voluntariedad para participar. Se estudiaron datos sociodemográficos, antecedentes patológicos personales, hábitos tóxicos y cumplimiento del esquema de vacunación. Resultados: El promedio de edad fue de 15 años, predominó el sexo femenino (51,7 por ciento), el color de la piel blanca (55,6 por ciento) y la valoración nutricional por encima del 75 hasta el 90 percentil (40,6 por ciento). El 9,6 por ciento tuvo hábitos tóxicos como hábito de fumar e ingestión de bebidas alcohólicas. El 51,2 por ciento presentó algún antecedente patológico personal, con mayor prevalencia para asma bronquial, rinitis y otras alergias. El 95,8 por ciento cumplió con el esquema de vacunación. Conclusiones: Las características sociodemográficas, los antecedentes patológicos personales y hábitos tóxicos descritos en los adolescentes del estudio son representativos para este grupo poblacional de Cuba. Se alcanzó un óptimo cumplimiento del esquema de vacunación(AU)

Introduction: The clinical evaluation of anti-COVID-19 vaccines in pediatric population, is a challenge in times of pandemic, to respond to the urgency of representative samples that contribute to the reproducibility of the study in the real population. Objective: To characterize the adolescents participating in the clinical trial with the Abdala anti-COVID-19 vaccine, to evaluate compliance with the vaccination schedule and to estimate whether they are representative of this population group. Methods: Data from a phase II trial with Abdala vaccine were used. A total of 703 subjects were included, 207 (29.4 percent) of them were adolescents, between 12 and 18 years of age, with apparently healthy or controlled chronic diseases, nutritional assessment between 10 and 90 percentiles, and willingness to participate in the study. Sociodemographic data, personal pathological history, toxic habits and compliance with the vaccination scheme of 3 doses every 14 days were the variables studied. Results: The average age was 15 years, it was predominant female sex (51.7 percent), white skin color (55.6 percent) and nutritional assessment above 75 to 90 percentiles (40.6 percent). The 9.6 percent had toxic habits such as smoking and ingestion of alcoholic beverages. Some personal pathological history was in 51.2 percent with a higher prevalence for bronchial asthma, rhinitis and other allergies. The vaccination scheme was fulfilled for 95.8 percent of individuals. Conclusions: Sociodemographic characteristics, pathological history and toxic habits described for adolescents on the study are representative for this population group in Cuba. The vaccination schedule had an optimal compliance(AU)

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Background: The pandemic of COVID-19 raised the urgent need for safe and efficacious vaccines against SARS-CoV-2. We evaluated the efficacy and safety of a new SARS-CoV-2 virus receptor-binding domain (RBD) vaccine. Methods: A phase 3, multicentre, randomised, double-blind, placebo-controlled trial was carried out at 18 clinical sites in three provinces of the south-eastern region of Cuba. Subjects (healthy or those with controlled chronic diseases) aged between 19 and 80 years, who gave written informed consent were eligible. Subjects were randomly assigned (1:1, in blocks) to two groups: placebo, and 50 µg RBD vaccine (Abdala). The product was administered intramuscularly, 0.5 mL in the deltoid region, in a three-dose immunization schedule at 0-14-28 days. The organoleptic characteristics and presentations of the vaccine and placebo were identical. All participants (subjects, clinical researchers, statisticians, laboratory technicians, and monitors) remained blinded during the study period. The main endpoint was to evaluate the efficacy of the Abdala vaccine in the prevention of symptomatic COVID-19. The trial is registered with the Cuban Public Registry of Clinical Trials, RPCEC00000359. Findings: Between March 22 to April 03, 2021, 48,290 subjects were included (24,144 and 24,146 in the placebo and Abdala groups, respectively) in the context of predominant D614G variant circulation. The evaluation of the main efficacy outcomes occurred during May-June 2021, starting at May 3rd, in the context of high circulation of mutant viruses, predominantly VOC Beta. The incidence of adverse reactions for individuals in the placebo and Abdala vaccine groups were 1227/24,144 (5.1%) and 1621/24,146 (6.7%), respectively. Adverse reactions were mostly mild, and from the injection site, which resolved in the first 24-48 h. No severe adverse events with demonstrated cause-effect relationship attributable to the vaccine were reported. Symptomatic COVID-19 disease was confirmed in 142 participants in the placebo group (78.44 incidence per 1000 person-years, 95% confidence interval [CI], 66.07-92.46) and in 11 participants in Abdala vaccine group (6.05 incidence per 1000 person years; 95% CI 3.02-10.82). The Abdala vaccine efficacy against symptomatic COVID-19 was 92.28% (95% CI 85.74-95.82). Moderate/serious forms of COVID-19 occurred in 30 participants (28 in the placebo group and only 2 in the Abdala vaccine group) for a vaccine efficacy of 92.88% (95% CI 70.12-98.31). There were five critical patients (of which four died), all in the placebo group. Interpretation: The Abdala vaccine was safe, well tolerated, and highly effective, fulfilling the WHO target product profile for COVID-19 vaccines. Those results, along with its immunization schedule and the advantage of easy storage and handling conditions at 2-8 °C, make this vaccine an option for the use in immunization strategies as a key tool for the control of the pandemic. Funding: Centre for Genetic Engineering and Biotechnology (CIGB), Havana, Cuba.

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Background: Multiple vaccine candidates against COVID-19 are currently being evaluated. We evaluate the safety and immunogenicity protein of a novel SARS-CoV-2 virus receptor-binding domain (RBD) vaccine. Methods: A phase 1-2, randomised, double-blind, placebo-controlled trial was carried out in "Saturnino Lora" Hospital, Santiago de Cuba, Cuba. Subjects (healthy or those with controlled chronic diseases) aged between 19 and 80 years, who gave written informed consent were eligible. Subjects were randomly assigned (1:1:1, in blocks) to three groups: placebo, 25 µg and 50 µg RBD vaccine (Abdala). The product was administered intramuscularly, 0·5 mL in the deltoid region. During the first phase, two immunization schedules were studied: 0-14-28 days (short) and 0-28-56 days (long). In phase 2, only the short schedule was evaluated. The organoleptic characteristics and presentations of vaccine and placebo were identical. All participants (subjects, clinical researchers, statisticians, laboratory technicians, and monitors) remained masked during the study period. The main endpoints were safety and the proportion of subjects with seroconversion of anti-RBD IgG antibodies, analysed by intention to treat and per protocol, respectively. The trial is registered with the Cuban Public Registry of Clinical Trials, RPCEC00000346. Findings: Between Dec 7, 2020, and Feb 9, 2021, 792 subjects were included; 132 (66 in each vaccination schedule, divided into 22 for each group) in phase 1, and 660 (220 in each group plus 66 from the short scheme of phase 1) in phase 2. The product was well tolerated. No severe adverse events were reported. During phase 1, the incidence of adverse events in the 25 µg, 50 µg, and placebo arms for the short schedule were 6/22 (27·3%), 6/22 (27·3%), 3/22 (13·6%), respectively, and for the long schedule were 8/22 (36·4%), 9/22 (40·9%), 4/22 (18·2%), respectively. In phase 2, adverse reactions were reported by 53/242 (21·9%), 75/242 (31·0%) and 41/242 (16·9%) participants in the 25 µg, 50 µg, and placebo group, respectively. Adverse reactions were minimal, mostly mild, and from the injection site, which resolved in the first 24-48 hours. In phase 1, seroconversion at day 56 was seen in 95·2% of the participants (20/21) in the 50 µg group, 81% (17/21) in the 25 µg group, and none in the placebo group (0/22). For the long schedule, seroconversion at day 70 was seen in 100% of the participants (21/21) in the 50 µg group, 94·7% (18/19) in the 25 µg group, and none in the placebo group (0/22). In phase 2, seroconversion of anti-RBD IgG antibodies at day 56 was seen in 89·2% of the participants in the 50 µg group (214/240; 95% CI 84·5-92·82), 77·7% in the 25 µg group (185/238; 72·0-82·9) and 4·6% in the placebo group (11/239; 2·3-8·1). Compared with the placebo arm, the differences in the proportion of participants with seroconversion were 73·1% (95% CI 66·8-79·5) and 84·6% (79·4-89·7) in the 25 µg and 50 µg groups, respectively. The seroconversion rate in the 50 µg group was significantly higher than in the 25 µg group (p=0·0012). Interpretation: The Abdala vaccine was safe, well tolerated, and induced humoral immune responses against SARS-CoV-2. These results, in the context of the emergency COVID-19 pandemic, support the 50 µg dose, applied in a 0-14-28 days schedule, for further clinical trials to confirm vaccine efficacy. Funding: Centre for Genetic Engineering and Biotechnology (CIGB), Havana, Cuba.