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      The effectiveness of mRNA‐1273 vaccine against COVID‐19 caused by Delta variant: A systematic review and meta‐analysis


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          We aimed to perform meta‐analyses to summarize the overall effectiveness of the mRNA‐1273 vaccine against COVID‐19 caused by the Delta variant from real‐world studies. A systematic literature search with no language restriction was performed in electronic databases to identify eligible observational studies that reported the effectiveness of the mRNA‐1273 vaccine to prevent reverse transcription‐polymerase chain reaction (RT‐PCR) confirmed COVID‐19 caused by Delta variant of SARS‐CoV‐2 (B.1.617.2). A random‐effects meta‐analysis model was used to estimate the pooled odds ratio (OR) at a 95% confidence interval (CI), and the vaccine effectiveness was indicated as (pooled OR − 1)/OR. Five studies were included for this systematic review and meta‐analysis. The meta‐analysis revealed that the administration of mRNA‐1273 vaccine protected against RT‐PCR confirmed COVID‐19 caused by Delta variant ≥21 days post first dose, with pooled vaccine effectiveness of 66% (95% CI: 65%–67%), as well as ≥14 days after the second dose, with pooled vaccine effectiveness of 91% (95% CI: 84%–95%). In conclusion, the mRNA‐1273 vaccine offers a substantial protection rate against RT‐PCR confirmed COVID‐19 caused by the Delta variant upon full vaccination, although with slightly reduced effectiveness relative to other strains of SARS‐CoV‐2.


          • Administration of mRNA‐1273 vaccine is 66% effective against COVID‐19 caused by Delta variant  21 days or more after the first dose.

          • Administration of mRNA‐1273 vaccine is 91% effective against COVID‐19 caused by Delta variant  14 days or more after the second dose.

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          SARS-CoV-2 B.1.617.2 Delta variant replication and immune evasion

          The B.1.617.2 (Delta) variant of severe acute respiratory syndrome coronavirus 2 (SARS-CoV-2) was first identified in the state of Maharashtra in late 2020 and spread throughout India, outcompeting pre-existing lineages including B.1.617.1 (Kappa) and B.1.1.7 (Alpha) 1 . In vitro, B.1.617.2 is sixfold less sensitive to serum neutralizing antibodies from recovered individuals, and eightfold less sensitive to vaccine-elicited antibodies, compared with wild-type Wuhan-1 bearing D614G. Serum neutralizing titres against B.1.617.2 were lower in ChAdOx1 vaccinees than in BNT162b2 vaccinees. B.1.617.2 spike pseudotyped viruses exhibited compromised sensitivity to monoclonal antibodies to the receptor-binding domain and the amino-terminal domain. B.1.617.2 demonstrated higher replication efficiency than B.1.1.7 in both airway organoid and human airway epithelial systems, associated with B.1.617.2 spike being in a predominantly cleaved state compared with B.1.1.7 spike. The B.1.617.2 spike protein was able to mediate highly efficient syncytium formation that was less sensitive to inhibition by neutralizing antibody, compared with that of wild-type spike. We also observed that B.1.617.2 had higher replication and spike-mediated entry than B.1.617.1, potentially explaining the B.1.617.2 dominance. In an analysis of more than 130 SARS-CoV-2-infected health care workers across three centres in India during a period of mixed lineage circulation, we observed reduced ChAdOx1 vaccine effectiveness against B.1.617.2 relative to non-B.1.617.2, with the caveat of possible residual confounding. Compromised vaccine efficacy against the highly fit and immune-evasive B.1.617.2 Delta variant warrants continued infection control measures in the post-vaccination era. A study of SARS-CoV-2 variants examining their transmission, infectivity, and potential resistance to therapies provides insights into the biology of the Delta variant and its role in the global pandemic.
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            Efficacy of the mRNA-1273 SARS-CoV-2 Vaccine at Completion of Blinded Phase

            Background At interim analysis in a phase 3, observer-blinded, placebo-controlled clinical trial, the mRNA-1273 vaccine showed 94.1% efficacy in preventing coronavirus disease 2019 (Covid-19). After emergency use of the vaccine was authorized, the protocol was amended to include an open-label phase. Final analyses of efficacy and safety data from the blinded phase of the trial are reported. Methods We enrolled volunteers who were at high risk for Covid-19 or its complications; participants were randomly assigned in a 1:1 ratio to receive two intramuscular injections of mRNA-1273 (100 μg) or placebo, 28 days apart, at 99 centers across the United States. The primary end point was prevention of Covid-19 illness with onset at least 14 days after the second injection in participants who had not previously been infected with the severe acute respiratory syndrome coronavirus 2 (SARS-CoV-2). The data cutoff date was March 26, 2021. Results The trial enrolled 30,415 participants; 15,209 were assigned to receive the mRNA-1273 vaccine, and 15,206 to receive placebo. More than 96% of participants received both injections, 2.3% had evidence of SARS-CoV-2 infection at baseline, and the median follow-up was 5.3 months in the blinded phase. Vaccine efficacy in preventing Covid-19 illness was 93.2% (95% confidence interval [CI], 91.0 to 94.8), with 55 confirmed cases in the mRNA-1273 group (9.6 per 1000 person-years; 95% CI, 7.2 to 12.5) and 744 in the placebo group (136.6 per 1000 person-years; 95% CI, 127.0 to 146.8). The efficacy in preventing severe disease was 98.2% (95% CI, 92.8 to 99.6), with 2 cases in the mRNA-1273 group and 106 in the placebo group, and the efficacy in preventing asymptomatic infection starting 14 days after the second injection was 63.0% (95% CI, 56.6 to 68.5), with 214 cases in the mRNA-1273 group and 498 in the placebo group. Vaccine efficacy was consistent across ethnic and racial groups, age groups, and participants with coexisting conditions. No safety concerns were identified. Conclusions The mRNA-1273 vaccine continued to be efficacious in preventing Covid-19 illness and severe disease at more than 5 months, with an acceptable safety profile, and protection against asymptomatic infection was observed. (Funded by the Biomedical Advanced Research and Development Authority and the National Institute of Allergy and Infectious Diseases; COVE ClinicalTrials.gov number, NCT04470427 .)
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              BNT162b2 and mRNA-1273 COVID-19 vaccine effectiveness against the SARS-CoV-2 Delta variant in Qatar

              With the global expansion of the highly transmissible SARS-CoV-2 Delta (B.1.617.2) variant, we conducted a matched test-negative case-control study to assess the real-world effectiveness of COVID-19 messenger RNA vaccines against infection with Delta in Qatar's population. BNT162b2 effectiveness against any, symptomatic or asymptomatic, Delta infection was 45.3% (95% CI, 22.0-61.6%) ≥14 d after the first vaccine dose, but only 51.9% (95% CI, 47.0-56.4%) ≥14 d after the second dose, with 50% of fully vaccinated individuals receiving their second dose before 11 May 2021. Corresponding mRNA-1273 effectiveness ≥14 d after the first or second dose was 73.7% (95% CI, 58.1-83.5%) and 73.1% (95% CI, 67.5-77.8%), respectively. Notably, effectiveness against Delta-induced severe, critical or fatal disease was 93.4% (95% CI, 85.4-97.0%) for BNT162b2 and 96.1% (95% CI, 71.6-99.5%) for mRNA-1273 ≥ 14 d after the second dose. Our findings show robust effectiveness for both BNT162b2 and mRNA-1273 in preventing Delta hospitalization and death in Qatar's population, despite lower effectiveness in preventing infection, particularly for the BNT162b2 vaccine.

                Author and article information

                J Med Virol
                J Med Virol
                Journal of Medical Virology
                John Wiley and Sons Inc. (Hoboken )
                18 January 2022
                May 2022
                18 January 2022
                : 94
                : 5 , Special Issue on New Coronavirus (2019‐nCoV or SARS‐CoV‐2) and the Outbreak of the Respiratory Illness (COVID‐19): Part‐XX ( doiID: 10.1002/jmv.v94.5 )
                : 2269-2274
                [ 1 ] School of Postgraduate Studies, International Medical University Kuala Lumpur Malaysia
                [ 2 ] School of Pharmacy, Monash University Malaysia Petaling Jaya Selangor Malaysia
                [ 3 ] School of Applied Sciences, University of Huddersfield Huddersfield UK
                [ 4 ] School of Biomedical Sciences & Pharmacy, University of Newcastle Callaghan Australia
                Author notes
                [*] [* ] Correspondence Chia S. Kow, International Medical University, Kuala Lumpur, Malaysia.

                Email: chiasiang_93@ 123456hotmail.com

                Author information
                © 2022 Wiley Periodicals LLC

                This article is being made freely available through PubMed Central as part of the COVID-19 public health emergency response. It can be used for unrestricted research re-use and analysis in any form or by any means with acknowledgement of the original source, for the duration of the public health emergency.

                : 03 November 2021
                : 28 December 2021
                Page count
                Figures: 2, Tables: 1, Pages: 6, Words: 2078
                Short Communication
                Short Communication
                Custom metadata
                May 2022
                Converter:WILEY_ML3GV2_TO_JATSPMC version:6.1.4 mode:remove_FC converted:18.04.2022

                Microbiology & Virology
                coronavirus,disease control,pathogenesis,respiratory tract,vaccines/vaccine strains,virus classification


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