tetano
Editor, Senior Moderator
Vaccine
. 2026 Mar 19:79:128424.
doi: 10.1016/j.vaccine.2026.128424. Online ahead of print.
Relative efficacy, safety, and immunogenicity analysis of two doses versus one dose of recombinant coronavirus vaccine (adenovirus type 5 vector) in adults 18 years and older: an international, multicentre, randomized, double blinded phase 3 trial
Adora Rooyakkers[SUP] 1 [/SUP], Lingyun Ye[SUP] 1 [/SUP], Pedro E Cahn[SUP] 2 [/SUP], Guillermo M Ruiz-Palacios[SUP] 3 [/SUP], Aamer Ikram[SUP] 4 [/SUP], Fernando Lanas[SUP] 5 [/SUP], Sergio Raúl Muñoz Navarro[SUP] 5 [/SUP], Omar Sued[SUP] 2 [/SUP], Dmitry A Lioznov[SUP] 6 [/SUP], Vitalina Dzutseva[SUP] 7 [/SUP], Ghazala Parveen[SUP] 8 [/SUP], Tatyana Zubkova[SUP] 6 [/SUP], Jingxin Li[SUP] 9 [/SUP], Joanne M Langley[SUP] 10 [/SUP], Ruijie Wang[SUP] 11 [/SUP], Luis Barreto[SUP] 11 [/SUP], Jinbo Gou[SUP] 11 [/SUP], Tao Zhu[SUP] 11 [/SUP], Carrie A Whittle[SUP] 1 [/SUP], Scott A Halperin[SUP] 12 [/SUP]; CanSino COVID-19 Global Efficacy Study Group
Affiliations
Background: An international, double-blind, placebo-controlled phase 3 study in healthy adults previously showed one dose of the Ad5-nCoV vaccine was efficacious (57.5%) against symptomatic COVID-19 infection, especially severe disease, was safe, and immunogenic (ClinicalTrials.gov, NCT04526990). The current study extends that report to assess relative vaccine efficacy (rVE), safety, and immunogenicity of two doses versus one dose of Ad5-nCoV vaccine.
Methods: Participants from the prior (part-one) study who continued to the follow-up study (part-two) herein were provided an Ad5-nCoV dose at study sites in Argentina, Chile, Mexico, Pakistan, and Russia, starting June 8th 2021 (median = 6 months post-first-injection). This injection led to two doses and one dose received by the prior vaccine and placebo recipients, respectively. Participants were monitored for COVID-19 disease, safety, and antibody responses up to 24 weeks post-vaccination.
Results: The endpoint of 83 cases occurred August 9, 2021, triggering primary efficacy analysis which evaluated rVE ≥10% (two versus one dose) of Ad5-nCoV in preventing PCR-confirmed COVID-19 disease at least 28 days post-vaccination. rVE (34.12%) was non-significant (95% CI -1.31 to 57.15, n = 8266), indicating similar efficacy of dose groups. End-of-study analysis (cutoff January 28, 2022) showed rVE was 6.3% (95% CI -8.7 to 19.2, starting 28 days), and for severe disease was 79.5% (95% CI 28.1% to 94.2%, starting 28 days). Serious adverse events (SAEs, ≥grade 4) were more frequent after one dose (12 [0.12%]) than two doses (4 [0.04%], p = 0.043), as were medically attended adverse events (9 [0.090%] and 1 [0.009%], p = 0.009). One SAE (myocarditis) was related to the study-product. Spike-RBD IgG and neutralization antibody titers were elevated for two-dose versus one-dose recipients (1.7- and 4.4-fold) at 28-days post-vaccination. Antibody responses waned by 24 weeks.
Conclusion: Two doses and one dose of Ad5-nCoV vaccine are efficacious, safe and immunogenic. A second dose improves protection against severe disease and immunogenicity.
Trial registration: The trial is registered at ClinicalTrials.gov (NCT04526990).
Keywords: Adenovirus type 5; Booster; Efficacy; Immunogenicity; Phase 3; SARS-CoV-2; Safety; Vaccine.
. 2026 Mar 19:79:128424.
doi: 10.1016/j.vaccine.2026.128424. Online ahead of print.
Relative efficacy, safety, and immunogenicity analysis of two doses versus one dose of recombinant coronavirus vaccine (adenovirus type 5 vector) in adults 18 years and older: an international, multicentre, randomized, double blinded phase 3 trial
Adora Rooyakkers[SUP] 1 [/SUP], Lingyun Ye[SUP] 1 [/SUP], Pedro E Cahn[SUP] 2 [/SUP], Guillermo M Ruiz-Palacios[SUP] 3 [/SUP], Aamer Ikram[SUP] 4 [/SUP], Fernando Lanas[SUP] 5 [/SUP], Sergio Raúl Muñoz Navarro[SUP] 5 [/SUP], Omar Sued[SUP] 2 [/SUP], Dmitry A Lioznov[SUP] 6 [/SUP], Vitalina Dzutseva[SUP] 7 [/SUP], Ghazala Parveen[SUP] 8 [/SUP], Tatyana Zubkova[SUP] 6 [/SUP], Jingxin Li[SUP] 9 [/SUP], Joanne M Langley[SUP] 10 [/SUP], Ruijie Wang[SUP] 11 [/SUP], Luis Barreto[SUP] 11 [/SUP], Jinbo Gou[SUP] 11 [/SUP], Tao Zhu[SUP] 11 [/SUP], Carrie A Whittle[SUP] 1 [/SUP], Scott A Halperin[SUP] 12 [/SUP]; CanSino COVID-19 Global Efficacy Study Group
Affiliations
- PMID: 41863180
- DOI: 10.1016/j.vaccine.2026.128424
Background: An international, double-blind, placebo-controlled phase 3 study in healthy adults previously showed one dose of the Ad5-nCoV vaccine was efficacious (57.5%) against symptomatic COVID-19 infection, especially severe disease, was safe, and immunogenic (ClinicalTrials.gov, NCT04526990). The current study extends that report to assess relative vaccine efficacy (rVE), safety, and immunogenicity of two doses versus one dose of Ad5-nCoV vaccine.
Methods: Participants from the prior (part-one) study who continued to the follow-up study (part-two) herein were provided an Ad5-nCoV dose at study sites in Argentina, Chile, Mexico, Pakistan, and Russia, starting June 8th 2021 (median = 6 months post-first-injection). This injection led to two doses and one dose received by the prior vaccine and placebo recipients, respectively. Participants were monitored for COVID-19 disease, safety, and antibody responses up to 24 weeks post-vaccination.
Results: The endpoint of 83 cases occurred August 9, 2021, triggering primary efficacy analysis which evaluated rVE ≥10% (two versus one dose) of Ad5-nCoV in preventing PCR-confirmed COVID-19 disease at least 28 days post-vaccination. rVE (34.12%) was non-significant (95% CI -1.31 to 57.15, n = 8266), indicating similar efficacy of dose groups. End-of-study analysis (cutoff January 28, 2022) showed rVE was 6.3% (95% CI -8.7 to 19.2, starting 28 days), and for severe disease was 79.5% (95% CI 28.1% to 94.2%, starting 28 days). Serious adverse events (SAEs, ≥grade 4) were more frequent after one dose (12 [0.12%]) than two doses (4 [0.04%], p = 0.043), as were medically attended adverse events (9 [0.090%] and 1 [0.009%], p = 0.009). One SAE (myocarditis) was related to the study-product. Spike-RBD IgG and neutralization antibody titers were elevated for two-dose versus one-dose recipients (1.7- and 4.4-fold) at 28-days post-vaccination. Antibody responses waned by 24 weeks.
Conclusion: Two doses and one dose of Ad5-nCoV vaccine are efficacious, safe and immunogenic. A second dose improves protection against severe disease and immunogenicity.
Trial registration: The trial is registered at ClinicalTrials.gov (NCT04526990).
Keywords: Adenovirus type 5; Booster; Efficacy; Immunogenicity; Phase 3; SARS-CoV-2; Safety; Vaccine.