A 2-dose regimen of the QazCovid-in® COVID-19 vaccine was safe and had high efficacy against COVID-19 infection, according to data from a phase 3 trial published in EClinical Medicine.
The QazCovid-in vaccine is a whole-virion formaldehyde-inactivated anti-COVID-19 vaccine. Between December 2020 and July 2021, a randomized, single-blinded, placebo-controlled trial was performed at 3 clinical centers in Kazakhstan to assess the safety and efficacy of the vaccine (ClinicalTrials.gov NCT04691908).
In total, 3000 participants aged 18 years and older were randomly assigned in a 4:1 fashion to receive either 2 doses of the vaccine 21 days apart or placebo. The follow-up period was 180 days, and the primary endpoint was the incidence of symptomatic COVID-19 infection confirmed by reverse transcription polymerase chain reaction testing at day 14 or later after receipt of the first vaccine dose.
Among participants who received the vaccine (n=2600) and those who received placebo (n=600), the median age was 35 (IQR, 26-45) and 34 (IQR, 26-46) years, 49.8% and 47.8% were women, and 5.5% and 7.7% were White.
The vaccine was found to be safe, with only local, short-lived adverse reaction occurring during the follow-up period. Within the 7 days following receipt of vaccination, the most common systemic adverse reaction among participants in the vaccine group was headache, occurring in 1.83% and 2.0% after receipt of the first and second doses of the vaccine, respectively. Of note, the safety of the vaccine no different among participants with concomitant diseases.
Between days 14 and 180, PCR-confirmed COVID-19 infection occurred among 31 participants in the vaccine group and 43 in the placebo group. There was 1 participant in the vaccine group with comorbid heart failure who developed severe COVID-19 infection. Overall, the vaccine had an efficacy rate of 82.0% (95% CI, 71.1-88.5).
This study was limited by its small sample size and the predominance of younger patients and those who were Asian. As this study was performed before the Omicron variant emerged in Kazakhstan, no data on the efficacy of the vaccine against this variant were available.
According to the researchers “these data indicate that the QazCovid-in vaccine promotes… protection not only against the SARS-CoV-2 strain used for vaccine preparation but also against [the] more transmissible Alpha and Delta [COVID-19] variants…”
Khairullin B, Zakarya K, Orynbayev M, et al. Efficacy and safety of an inactivated whole-virion vaccine against COVID-19, QazCovid-in®, in healthy adults: A multicentre, randomised, single-blind, placebo-controlled phase 3 clinical trial with a 6-month follow-up. EClinicalMedicine. Published online June 25, 2022. doi: 10.1016/j.eclinm.2022.101526