Journal of Vaccine Research 2024, Vol.14, No.5, 231-242 http://medscipublisher.com/index.php/jvr 235 Moreover, booster doses have been shown to enhance protection against various VOCs. For example, a study on the inactivated COVID-19 vaccine BBV152 (Covaxin) reported that a third dose significantly elevated neutral 5 Case Studies of Vaccine Effectiveness Against Variants 5.1 Case study 1: vaccine effectiveness in the U.S. against alpha and delta variants In the United States, the effectiveness of COVID-19 vaccines against the Alpha (B.1.1.7) and Delta (B.1.617.2) variants has been extensively studied. The mRNA vaccines, particularly BNT162b2 (Pfizer-BioNTech) and mRNA-1273 (Moderna), have shown high efficacy against these variants. A study conducted across 21 hospitals in the U.S. found that two doses of mRNA vaccines were 85% effective in preventing hospital admissions due to the Alpha variant and 85% effective against the Delta variant. However, the effectiveness against the Delta variant increased to 94% with a third dose (Figure 2) (Lauring et al., 2022). Figure 2 Vaccine effectiveness (VE) of mRNA vaccines to prevent hospital admissions with covid-19 by variant group, including alpha, delta, and omicron (Adopted from Lauring et al., 2022) Image caption: Groups with ≥150 cases and controls were reported. Groups with <150 cases or <150 controls were not reported owing to low precision of VE estimates with these sample sizes. †Obtained using structured medical chart review, and defined as one or more of the following: active solid organ cancer (active cancer defined as treatment for the cancer or newly diagnosed cancer in past six months), active hematologic cancer, HIV infection without AIDS, AIDS, congenital immunodeficiency syndrome, previous splenectomy, previous solid organ transplant, immunosuppressive drugs, systemic lupus erythematosus, rheumatoid arthritis, psoriasis, scleroderma, or inflammatory bowel disease, including Crohn’s disease or ulcerative colitis. ‡Obtained using structured medical chart review, and defined as conditions within one or more of the following categories: cardiovascular disease, neurologic disease, pulmonary disease, gastrointestinal disease, endocrine disease, renal disease, hematologic disease, malignancy, immunosuppression not captured in other categories, autoimmune condition, or other condition (sarcoidosis, amyloidosis, or unintentional weight loss ≥10 pounds (4.5 kg) in past 90 days)
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