Inactivated whole-virion SARS-CoV-2 vaccine reduces rates of symptomatic COVID-19 infections [Classics Series]

This study summary is an excerpt from the book 2 Minute Medicine’s The Classics in Medicine: Summaries of the Landmark Trials

1. Incidence of PCR-confirmed symptomatic COVID-19 cases was lower in the vaccine group compared with the placebo group.

2. The majority of adverse events were mild and there was no vaccine-related mortality.

Original Date of Publication: July 2021

Study Rundown: Inactivated vaccines offer a variety of benefits against transmission of severe acute respiratory syndrome coronavirus 2 (SARS-CoV-2). One such inactivated whole-virion vaccine is CoronaVac, which is currently in phase 3 trials in Brazil, Indonesia, Chile, and Turkey. This phase III randomized controlled trial aimed to assess the safety and efficacy of CoronaVac in Turkey. The primary outcome for this study was the proportion of laboratory confirmed COVID-19 cases at least 14 days after administering the second dose, while key secondary outcomes included incidence of hospitalization, adverse events, and mortality. According to study results, the vaccine group reported significantly fewer cases of symptomatic COVID-19 compared with placebo; however, the frequency of adverse events was higher in the former. In addition, no individuals in the vaccine group required hospitalization for their infection. While this study was well done, a major limitation was that it did not explore the impact of vaccine interchangeability on the aforementioned clinical outcomes. Nevertheless, it provides valuable insight into the use of CoronaVac for safe and effective immunogenicity during the COVID-19 pandemic.

Click to read the study in the Lancet

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In-Depth [randomized control trial]: Between September 14, 2020, and January 5, 2021, 11 303 patients were assessed for eligibility across 24 centers in Turkey. Included patients were between 18-59 years of age with no previous history of COVID-19 and a negative SARS-CoV-2 PCR or antibody test. Those diagnosed with a bleeding disorder or on immunosuppressants were excluded. Altogether, 10 214 patients in the intention-to-treat group (65.1% in vaccine group vs. 34.9% in placebo group) and 10 029 patients in the per-protocol group (65.4% in vaccine group vs. 34.6% in placebo group) completed the trial. Median age among enrolled patients was 45 years (interquartile range [IQR] 37-51) and the majority (57.8%) were male.

Tanriover MD, Doğanay HL, Akova M, Güner HR, Azap A, Akhan S, et al. Efficacy and safety of an inactivated whole-virion SARS-CoV-2 vaccine (CoronaVac): interim results of a double-blind, randomised, placebo-controlled, phase 3 trial in Turkey. The Lancet. 2021 Jul 17;398(10296):213–22.

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