Effectiveness of mRNA COVID-19 Vaccines in Adolescents Over 6 Months

Abstract

BACKGROUND AND OBJECTIVES On June 4, 2021, Italy launched the COVID-19 vaccination of adolescents to pace down the COVID-19 spread. Although clinical trials have evaluated mRNA vaccine effectiveness in adolescents, there is limited literature on its real-world effectiveness. Accordingly, this study aimed to estimate the effectiveness of mRNA COVID-19 vaccines against SARS-CoV-2 infection and mild or severe COVID-19 in a cohort of Sicilian adolescents within a six-month observation period. METHODS A retrospective cohort study was conducted with adolescents aged 12–18, residents of Sicily, that were followed from July 15 to December 31, 2021. SARS-CoV-2 infections, mild and severe COVID-19, and COVID-19-related intubation or deaths during the study period were compared between subjects vaccinated with two doses of mRNA vaccines and unvaccinated individuals. The Cox regression analysis, adjusted for age and sex, was performed to compare the two groups. RESULTS Overall, the study included a total at-risk population of 274,782 adolescents with 61.4% (168,633) of them having completed the vaccination cycle by the end of the study. Unvaccinated subjects had higher incidence rates of SARS-CoV-2 (1,043 x 10,000 vs. 158.7 x 10,000 subjects), mild COVID-19 (27.7 x 10,000 vs. 1.8 x 10,000 subjects) and severe COVID-19 (1.41 x 10,000 vs. 0 subjects) compared to the vaccinated population. The estimated adjusted vaccine effectiveness against SARS-CoV-2 infection was 71.2%, reaching 92.1% and 97.9% against mild and severe COVID-19, respectively. CONCLUSIONS This study provides rigorous evidence of the mRNA COVID-19 vaccines effectiveness in protecting adolescents from both SARS-CoV-2 infection, and mild or severe COVID-19.

Immunogenicity, effectiveness, and safety of COVID-19 vaccines among children and adolescents aged 2–18 years: an updated systematic review and meta-analysis

“…Of the 88 articles included, there were 12 RCTs, two non-randomized clinical trials, 40 cohort studies, 19 cross-sectional studies, and 15 case‒control studies. In the studies included, 16 articles were available for immunogenicity analysis (Supplementary Table 2) [ 14 , 15 , 18 , 31 – 43 ]; 38 articles were available for effectiveness analysis (Supplementary Table 3) [ 14 , 17 , 19 , 31 , 44 – 77 ]; and 49 articles were available for safety analysis (Supplementary Table 4) [ 14 – 16 , 18 , 20 – 24 , 31 , 34 , 35 , 37 , 41 , 43 , 45 , 47 , 50 , 55 , 78 – 107 ]. Children and adolescents are involved in 27 countries, including the United States, China, Australia, Argentina, Italy, Israel, France, Denmark, and South Korea, which have larger cohorts (> 100,000 people).…”

Effectiveness of mRNA Vaccine Booster against SARS-CoV-2 Infection and COVID-19 in the Adult Population during the First Three Months of the Omicron Wave in Sicily

“…According to the Italian National Classification Criteria in terms of COVID-19 severity, we considered as "severe COVID-19" each SARS-CoV-2 positive patient with clinical manifestations of the respiratory tract/other organs that required hospitalization or admission to the intensive care unit [25]. "Intubation/death from COVID-19" status information was obtained from hospital records.…”

Pädiatrie aktuell – Forschung kurz notiert

“…In der darauf folgenden 2. Jahreshälfte 2021 wurde die Effektivität der Impfung bei 274.782 sizilianischen Jugendlichen untersucht [ 2 ]. Dabei zeigte sich – bezogen auf jeweils 10.000 Personen – bei den Geimpften eine deutlich niedrigere Rate an Infektionen als bei Ungeimpften (158,7 vs. 1043), an milden Erkrankungen (1,8 vs. 27,7) sowie an schweren Erkrankungen (1,4 vs. 0).…”