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A better understanding of the long-term safety, efficacy, and immunogenicity of COVID-19 vaccines is needed. This phase 3, randomized, placebo-controlled study for AZD1222 (ChAdOx1 nCoV-19) primary-series vaccination enrolled 32,450 participants in the USA, Chile, and Peru between August 2020 and January 2021 (NCT04516746). Endpoints included the 2-year follow-up assessment of safety, efficacy, and immunogenicity. After 2 years, no emergent safety signals were observed for AZD1222, and no cases of thrombotic thrombocytopenia syndrome were reported. The assessment of anti-SARS-CoV-2 nucleocapsid antibody titers confirmed the durability of AZD1222 efficacy for up to 6 months, after which infection rates in the AZD1222 group increased over time. Despite this, all-cause and COVID-19-related mortality remained low through the study end, potentially reflecting the post-Omicron decoupling of SARS-CoV-2 infection rates and severe COVID-19 outcomes. Geometric mean titers were elevated for anti-SARS-CoV-2 neutralizing antibodies at the 1-year study visit and the anti-spike antibodies were elevated at year 2, providing further evidence of increasing SARS-CoV-2 infections over long-term follow-up. Overall, this 2-year follow-up of the AZD1222 phase 3 study confirms that the long-term safety profile remains consistent with previous findings and supports the continued need for COVID-19 booster vaccinations due to waning efficacy and humoral immunity.
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; Lan, Dongmei 1 ; Olsson, Urban 9 ; Senthilkumar Saminathan 10 ; Shankar, Nirmal Kumar 10 ; Villegas, Berta 11 ; Villafana, Tonya 2 ; Falsey, Ann R 12 ; Sobieszczyk, Magdalena E 5 1 Biometrics, Vaccines & Immune Therapies, BioPharmaceuticals R&D, AstraZeneca, Gaithersburg, MD 20878, USA;
2 Clinical Development, Vaccines & Immune Therapies, BioPharmaceuticals R&D, AstraZeneca, Gaithersburg, MD 20878, USA;
3 Division of Infectious Diseases, Department of Medicine, University of Rochester, Rochester, NY 14627, USA;
4 Division of Infectious Diseases, Rush University Medical Center, Chicago, IL 60612, USA;
5 Division of Infectious Diseases, Department of Medicine, Vagelos College of Physicians and Surgeons, New York-Presbyterian/Columbia University Irving Medical Center, New York, NY 10032, USA;
6 Formerly Patient Safety, Vaccines & Immune Therapies, BioPharmaceuticals R&D, AstraZeneca, Cambridge CB2 0AA, UK;
7 Clinical Development, Vaccines & Immune Therapies, BioPharmaceuticals R&D, AstraZeneca, Cambridge CB2 0AA, UK
8 Formerly Translational Medicine, Vaccines & Immune Therapies, BioPharmaceuticals R&D, AstraZeneca, Gaithersburg, MD 20878, USA;
9 Clinical Development, Vaccines & Immune Therapies, BioPharmaceuticals R&D, AstraZeneca, 431 83 Gothenburg, Sweden;
10 Patient Safety, Chief Medical Office, R&D, AstraZeneca, Bangalore 560045, India;
11 Clinical Operations, Vaccines & Immune Therapies, BioPharmaceuticals R&D, AstraZeneca, Mississauga, ON L4Y 1M4, Canada;
12 Department of Medicine, Infectious Diseases, University of Rochester School of Medicine and Dentistry, Rochester, New York, NY 14642, USA;