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Effect of 2 Inactivated SARS-CoV-2 Vaccines on Symptomatic COVID-19 Infection in Adults: A Randomized Clinical Trial
Nawal Al Kaabi1, Yuntao Zhang2, Shengli Xia3
1Sheikh Khalifa Medical City, Abu Dhabi Health Services Company (SEHA), Abu Dhabi, United Arab Emirates.
Importance:
Although effective vaccines against COVID-19 have been developed, additional vaccines are still needed.
Objective:
To evaluate the efficacy and adverse events of 2 inactivated COVID-19 vaccines.
Design, Setting, And Participants:
Prespecified interim analysis of an ongoing randomized, double-blind, phase 3 trial in the United Arab Emirates and Bahrain among adults 18 years and older without known history of COVID-19. Study enrollment began on July 16, 2020. Data sets used for the interim analysis of efficacy and adverse events were locked on December 20, 2020, and December 31, 2020, respectively.
Interventions:
Participants were randomized to receive 1 of 2 inactivated vaccines developed from SARS-CoV-2 WIV04 (5 µg/dose; n = 13 459) and HB02 (4 µg/dose; n = 13 465) strains or an aluminum hydroxide (alum)-only control (n = 13 458); they received 2 intramuscular injections 21 days apart.
Main Outcomes And Measures:
The primary outcome was efficacy against laboratory-confirmed symptomatic COVID-19 14 days following a second vaccine dose among participants who had no virologic evidence of SARS-CoV-2 infection at randomization. The secondary outcome was efficacy against severe COVID-19. Incidence of adverse events and reactions was collected among participants who received at least 1 dose.
Results:
Among 40 382 participants randomized to receive at least 1 dose of the 2 vaccines or alum-only control (mean age, 36.1 years; 32 261 [84.4%] men), 38 206 (94.6%) who received 2 doses, contributed at least 1 follow-up measure after day 14 following the second dose, and had negative reverse transcriptase-polymerase chain reaction test results at enrollment were included in the primary efficacy analysis. During a median (range) follow-up duration of 77 (1-121) days, symptomatic COVID-19 was identified in 26 participants in the WIV04 group (12.1 [95% CI, 8.3-17.8] per 1000 person-years), 21 in the HB02 group (9.8 [95% CI, 6.4-15.0] per 1000 person-years), and 95 in the alum-only group (44.7 [95% CI, 36.6-54.6] per 1000 person-years), resulting in a vaccine efficacy, compared with alum-only, of 72.8% (95% CI, 58.1%-82.4%) for WIV04 and 78.1% (95% CI, 64.8%-86.3%) for HB02 (P < .001 for both). Two severe cases of COVID-19 occurred in the alum-only group and none occurred in the vaccine groups. Adverse reactions 7 days after each injection occurred in 41.7% to 46.5% of participants in the 3 groups; serious adverse events were rare and similar in the 3 groups (WIV04: 64 [0.5%]; HB02: 59 [0.4%]; alum-only: 78 [0.6%]).
Conclusions And Relevance:
In this prespecified interim analysis of a randomized clinical trial, treatment of adults with either of 2 inactivated SARS-CoV-2 vaccines significantly reduced the risk of symptomatic COVID-19, and serious adverse events were rare. Data collection for final analysis is pending.
Trial Registration:
ClinicalTrials.gov Identifier: NCT04510207; Chinese Clinical Trial Registry: ChiCTR2000034780.
Insights
Two inactivated vaccines against COVID-19 (SARS-CoV-2) demonstrated significant efficacy in preventing symptomatic illness. Serious adverse events were rare in this phase 3 trial, indicating a favorable safety profile for both vaccines.
Area of Science:
- Vaccinology
- Infectious Diseases
- Clinical Trials
Background:
- Effective vaccines are crucial for controlling the COVID-19 pandemic.
- Additional vaccine candidates are needed to meet global demand and address potential variants.
Purpose of the Study:
- To assess the efficacy and safety of two inactivated vaccines against SARS-CoV-2.
- To compare the performance of two distinct inactivated COVID-19 vaccines in a randomized controlled trial.
Main Methods:
- A randomized, double-blind, placebo-controlled phase 3 trial involving adults without prior COVID-19.
- Participants received two intramuscular injections of either inactivated SARS-CoV-2 vaccine (WIV04 or HB02) or an aluminum hydroxide (alum)-only control.
- Efficacy was measured against symptomatic COVID-19, with safety assessed through adverse event monitoring.
Main Results:
- Vaccine efficacy against symptomatic COVID-19 was 72.8% for WIV04 and 78.1% for HB02 compared to the control group.
- No severe COVID-19 cases occurred in the vaccine groups, versus two in the control group.
- Adverse reactions were common but mild, and serious adverse events were rare and similar across all groups.
Conclusions:
- The two inactivated SARS-CoV-2 vaccines are effective in preventing symptomatic COVID-19.
- The vaccines exhibit a favorable safety profile with rare serious adverse events.
- Further data collection is ongoing for the final analysis of these COVID-19 vaccines.
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