Table 1.

Characteristics of included vaccination trials investigating the efficacy of COVID-19

Authors (NCT number), Design and enrollment period	Country (number of study sites)	Population (age, range)	Sample (% of men)	Vaccines: type, dosing information, and schedule (number of participants)	Control (number of participants)	Storage, conditions	Number of dose and route of administration	Primary outcomes	Sponsorship	Overall risk of bias
Polack, 2020 (NCT04368728), Phase 2–3randomized, observer-blind, placebo-controlled trial; July 27, 2020 to November 14, 2020	US (130 sites), Argentina (1 site), Brazil (2 sites), South Africa (4 sites), Germany (6 sites), and Turkey (9 sites)	Healthy or stable chronic disease condition: HIV, HBV, HCV (16 years or older)	43,448 (50.6)	BNT162b2 (lipid nanoparticle-formulated, nucleoside-modified RNA encoding the SARS-CoV-2 full-length spike): 30 μg (n=21,720)	Placebo (sterile saline, 0.9% sodium chloride n=21,728)	-80° to -60°C; 2-8°C for 30 days; room temperature ≤ 2h	Two doses 21 days apart in intramuscular in the deltoid muscle	Efficacy of BNT162b2 against confirmed COVID-19 with onset at least 7 days after the second dose in participants who had been without serologic or virologic evidence of SARS-CoV-2 infection up to 7 days after the second dose.	BioNTech and Pfizer	High
Voysey, 2020 (NCT04400838, NCT04444674), Phase 2–3 randomized, single-blind (COV002, UK), Phase 3 randomized, single-blind (COV003, Brazil); April 23, 2020 to November 4, 2020	UK (19 sites), Brazil (6 sites)	Professions with high risk exposure to virus (Health or social care workers, 18 years or older)	11,636 (39.5)	ChAdOx1 nCoV-19 (AZS1222): recombinant-deficient chimpanzee adenoviral vector containing the SARS-CoV-2 structural glycoprotein antigen (spike protein; nCoV-19) COV002: (two doses) LD/SD Low dose (LD): 2.2 ×1010 VP followed by a Standard-dose (SD): 3.5–6.5×1010 VP; n=1367) Two standards doses: SD/SD (n=2277) COV003 (two doses) Standard-dose (3.5–6.5×1010 VP; n=2063)	COV002 (LD/SD): Meningococcal group A, C, W, and Y conjugate vaccine (MenACWY; n=1374) COV002 (SD/SD): MenACWY (n=2430) COV003: MenACWY for the first dose and saline for the second dose (n=2,025)	2-8°C for 6 months;	Two doses 21 days apart in intramuscular in the deltoid muscle	Efficacy of ChAdOx1 nCoV-19 against virologically confirmed, symptomatic COVID-19, defined as a nucleic acid amplification test-positive swab (NAAT) positive swab combined with at least one qualifying symptom (fever ≥ 37.8°C, cough, shortness of breath, anosmia, or aguesia) in seronegative participants more than 14 days after a second dose.	UK Research and Innovation, National Institute of Health Research (NIHR), Coalition for Epidemic Preparedness Innovations, NIHR Oxford Biomedical Research Centre, Thames Valley and South Midlands NIHR Clinical Research Network, and AstraZeneca	High
Baden, 2020 (NCT04470427), Phase 3 randomized, observer-blind, placebo-controlled trial; July 27, 2020 to October 23, 2020	US (99 sites)	18 years or older persons at high risk for SARS-COV-2 infection, a high risk of severe COVID-19 or both	30,420 (52.7)	mRNA-1273 lipid nanoparticle (LNP)-encapsulated modified RNA encoding the perfusion stabilized full-length spike protein of the SARS-CoV-2 virus): 100 μg (n=15,210)	Saline placebo (n=15,210)	-25° to -15°C 2-8°C for 30 days; room temperature ≤ 12h	Two doses 28 days apart in intramuscular in the deltoid muscle	Efficacy of mRNA-1273 against confirmed SARS-CoV-2 with onset at least 14 days after the second dose in participants who had not previously been infected with SARS-CoV-2 virus (seronegative).	National Institute of Allergy and Infectious Diseases; Moderna	High
Al Kaabi, 2021 (NCT04510207, ChiCRT2000034780) Phase 3 randomized, double-blind; July 16, 2020 to December 31, 2020	United Arab Emirates (UAE), Bahrain, India, China, Syria, Nepal, Egypt, Pakistan, Philippine, and Bangladesh (10 sites)	18 years or older without prior known history of SARS-CoV, SARS-CoV-2, or Middle East respiratory syndrome infection	40,411 (84.4%)	Two inactivated SARS-CoV-2 strains created from Vero cells with aluminum hydroxide adjuvant (WIV04 and HB02) WIV04: 5 μg (n=13,470) HB02: 4 μg (n=13,470)	Aluminum hydroxide (alum)-only (n=13,471)	2-8°C; lifespan unknown	Two doses 21 days apart in intramuscular in the deltoid muscle	Efficacy against laboratory-confirmed symptomatic COVID-19 cases 14 days following a second dose among participants who had no virologic evidence of SARS-CoV-2 infection at randomization	National Key Research and Development Project of China (2020YFC082100); Wuhan Institute of Biological Products Co. Ltd., Beijing Institute of Biological Products Co. Ltd. (Sinopharm).	High
Logunov, 2020 (NCT04530396), Phase 2–3 randomized, double-blind, placebo-controlled trial; September 7, 2020 to November 24, 2020	Russia, Moscow (25 sites)	Participants aged at least 18 years, with negative SARS-CoV-2 PCR and IgG and IgM tests, no infectious diseases in the 14 days before enrollment, and no other vaccinations in the 30 days before enrollment	21,862 (56)	Heterologous prime-boost which combined two vector vaccine based on rAd type 26 (rAd26) and rAd type 5 (rAd5) carrying the gene for SARS-CoV-2 full-length glycoprotein S Prime: rAd26 Boost: rAd5 (n=16,427)	Saline placebo (n=5435)	-18°C (Liquid form); 2-8°C (freeze dried) for up to 6 months	Two doses 21 days apart in intramuscular in the deltoid muscle	Efficacy of vaccine measured as the proportion of participants with COVID-19 confirmed by PCR from day 21 after receiving the first dose.	Moscow City Health Department, Russian Direct Investment Fund, Sberbank, and RUSAL	High
Sadoff, 2021 (NCT04505722) Phase 3 randomized, double-blind, placebo-controlled trial; (ENSEMBLE), September 21, 2020 to November 24, 2020	US, Chile, Peru, Mexico, Argentina, Brazil, Colombia, South Africa	Participants with good or stable healthy, without coexisting conditions aged 18 years or older	43,783 (54.9)	Ad26.COV2.S: replication-incompetent adenovirus type 26 (Ad26) vectored vaccine encoding a stabilized variant of the SARS-CoV-2 S protein (5×1010 VP; n=21,895)	Saline placebo (n=21,888)	-20°C; 2-8°C for 3 months	Single dose in intramuscular in the deltoid muscle	Co-primary efficacies endpoints against the first occurrence of centrally confirmed, moderate to severe/critical COVID-19 with onset at least 14 and 18 days in the per-protocol population who had tested negative for SARS-CoV-2	Janssen/Johnson & Johnson	High
Heath, 2021 (EudraCT number, 2020-004123-16) Phase 3 randomized, observer-blind, placebo-controlled trial (2019nCoV-302); September 28, 2020 to November 28, 2020	UK (33 sites)	Participants aged 18 and 84 years with health or stable chronic medical conditions (HIV, cardiac and respiratory diseases)	15,185 (51.6)	NVX-CoV2373: recombinant nanoparticle encoding the full-length spike glycoprotein of the prototype strain plus Matrix-M adjuvant (5 μg of NVX-CoV2373 plus 50 μg of Matrix-M adjuvant; n=7,593)	Saline placebo (n=7,594)	2-8°C for 3 months	Two doses 21 days apart in intramuscular in the deltoid muscle	Efficacy of virologically confirmed mild, moderate, or severe SARS-CoV-2 infection with an onset at least 7 days after the second dose in participants who were serologically negative at baseline	Novavax	High
Tanriover, 2021 (NCT04582344) Phase 3 randomized, double-blind, placebo-controlled trial; September 14, 2020 to January 05, 2021	Turkey (24 sites)	Volunteers aged 18-59 years without history of COVID-19 and with negative PCR and antibody test results for SARS-CoV-2	10,214 (57.8)	CoronaVac: inactivated whole-virion SARS-CoV-2 vaccine (3 μg of SARS-CoV-2 virion plus 0.45 mg/ml of aluminium hydroxide; n=6,646)	Placebo (n=3,568)	2-8°C for 12-14 h	Two doses 14 days apart in intramuscular in the deltoid muscle	Efficacy of PCR-confirmed symptomatic COVID-19 at least 14 days after the second dose in the per-protocol population	Turkish Health Institutes Association	High

COVID-19, coronavirus disease; US, United States; UK, United Kingdom; HIV, human immunodeficiency virus; HBV, hepatitis B virus; HCV, hepatitis C virus; RT-PCR, reverse transcriptase-polymerase chain reaction; LD, low dose; SD, standard dose; VP, viral particle