• Vivek Shinde, Sutika Bhikha, Zaheer Hoosain, Moherndran Archary, Qasim Bhorat, Lee Fairlie, Umesh Lalloo, Mduduzi S L Masilela, Dhayendre Moodley, Sherika Hanley, Leon Fouche, Cheryl Louw, Michele Tameris, Nishanta Singh, Ameena Goga, Keertan Dheda, Coert Grobbelaar, Gertruida Kruger, Nazira Carrim-Ganey, Vicky Baillie, Tulio de Oliveira, Anthonet Lombard Koen, Johan J Lombaard, Rosie Mngqibisa, As'ad E Bhorat, Gabriella Benadé, Natasha Lalloo, Annah Pitsi, Pieter-Louis Vollgraaff, Angelique Luabeya, Aliasgar Esmail, Friedrich G Petrick, Aylin Oommen-Jose, Sharne Foulkes, Khatija Ahmed, Asha Thombrayil, Lou Fries, Shane Cloney-Clark, Mingzhu Zhu, Chijioke Bennett, Gary Albert, Emmanuel Faust, Joyce S Plested, Andreana Robertson, Susan Neal, Iksung Cho, Greg M Glenn, Filip Dubovsky, Shabir A Madhi, and 2019nCoV-501 Study Group.
• From Novavax, Gaithersburg, MD (V.S., L. Fries, S.C.-C., M.Z., C.B., G.A., E.F., J.S.P., A.R., S.N., I.C., G.M.G., F.D.); and the South African Medical Research Council, Vaccines and Infectious Diseases Analytics Research Unit, Faculty of Health Sciences (S.B., V.B., A.L.K., A.O.-J., A.T., S.A.M.), Wits Reproductive Health and HIV Institute (L. Fairlie, G.B.), University of the Witwatersrand, and Soweto Clinical Trials Centre (Q.B., A.E.B.), Johannesburg, Josha Research Centre, Bloemfontein (Z.H., J.J.L., S.F.), the Paediatric Infectious Diseases Unit (M.A., R.M.), the Respiratory and Critical Care Unit (U.L., N.L.), the Department of Obstetrics and Gynaecology (D.M.), Centre for the AIDS Programme of Research in South Africa (S.H.), and Kwazulu-Natal Research Innovation and Sequencing Platform (T.O.), Nelson R. Mandela School of Medicine, University of KwaZulu-Natal, Durban, the Setshaba Research Centre, Tshwane (M.S.L.M., A.P., K.A.), the Limpopo Clinical Research Initiative, Rustenburg (L. Fouche, P.-L.V.), the Madibeng Centre for Research, Department of Family Medicine, School of Health, University of Pretoria (C.L.), and the Aurum Institute (C.G.), Pretoria, the South African TB Vaccine Initiative (M.T., N.S., A.L.) and the Centre for Lung Infection and Immunity, Division of Pulmonology, Department of Medicine, and UCT Lung Institute (K.D., A.E.), University of Cape Town, and the Health Systems Research Unit and the HIV Prevention Research Unit, South African Medical Research Council (N.S., A.G.), Cape Town, Mzansi Ethical Research Centre, Middelburg (G.K., F.G.P.), and Peermed Clinical Trial Centre, Kempton Park (N.C.-G.) - all in South Africa.
• N. Engl. J. Med. 2021 May 20; 384 (20): 189919091899-1909.

BackgroundThe emergence of severe acute respiratory syndrome coronavirus 2 (SARS-CoV-2) variants threatens progress toward control of the coronavirus disease 2019 (Covid-19) pandemic. In a phase 1-2 trial involving healthy adults, the NVX-CoV2373 nanoparticle vaccine had an acceptable safety profile and was associated with strong neutralizing-antibody and antigen-specific polyfunctional CD4+ T-cell responses. Evaluation of vaccine efficacy was needed in a setting of ongoing SARS-CoV-2 transmission.MethodsIn this phase 2a-b trial in South Africa, we randomly assigned human immunodeficiency virus (HIV)-negative adults between the ages of 18 and 84 years or medically stable HIV-positive participants between the ages of 18 and 64 years in a 1:1 ratio to receive two doses of either the NVX-CoV2373 vaccine (5 μg of recombinant spike protein with 50 μg of Matrix-M1 adjuvant) or placebo. The primary end points were safety and vaccine efficacy against laboratory-confirmed symptomatic Covid-19 at 7 days or more after the second dose among participants without previous SARS-CoV-2 infection.ResultsOf 6324 participants who underwent screening, 4387 received at least one injection of vaccine or placebo. Approximately 30% of the participants were seropositive for SARS-CoV-2 at baseline. Among 2684 baseline seronegative participants (94% HIV-negative and 6% HIV-positive), predominantly mild-to-moderate Covid-19 developed in 15 participants in the vaccine group and in 29 in the placebo group (vaccine efficacy, 49.4%; 95% confidence interval [CI], 6.1 to 72.8). Vaccine efficacy among HIV-negative participants was 60.1% (95% CI, 19.9 to 80.1). Of 41 sequenced isolates, 38 (92.7%) were the B.1.351 variant. Post hoc vaccine efficacy against B.1.351 was 51.0% (95% CI, -0.6 to 76.2) among the HIV-negative participants. Preliminary local and systemic reactogenicity events were more common in the vaccine group; serious adverse events were rare in both groups.ConclusionsThe NVX-CoV2373 vaccine was efficacious in preventing Covid-19, with higher vaccine efficacy observed among HIV-negative participants. Most infections were caused by the B.1.351 variant. (Funded by Novavax and the Bill and Melinda Gates Foundation; ClinicalTrials.gov number, NCT04533399.).Copyright © 2021 Massachusetts Medical Society.

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