Effect of an Inactivated Vaccine Against SARS-CoV-2 on Safety and Immunogenicity Outcomes

Abstract

IMPORTANCE A vaccine against coronavirus disease 2019 (COVID-19) is urgently needed. OBJECTIVE To evaluate the safety and immunogenicity of an investigational inactivated whole-virus COVID-19 vaccine in China. INTERVENTIONS In the phase 1 trial, 96 participants were assigned to 1 of the 3 dose groups (2.5, 5, and 10 μg/dose) and an aluminum hydroxide (alum) adjuvant-only group (n = 24 in each group), and received 3 intramuscular injections at days 0, 28, and 56. In the phase 2 trial, 224 adults were randomized to 5 μg/dose in 2 schedule groups (injections on days 0 and 14 [n = 84] vs alum only [n = 28], and days 0 and 21 [n = 84] vs alum only [n = 28]). DESIGN, SETTING, AND PARTICIPANTS Interim analysis of ongoing randomized, double-blind, placebo-controlled, phase 1 and 2 clinical trials to assess an inactivated COVID-19 vaccine. The trials were conducted in Henan Province, China, among 96 (phase 1) and 224 (phase 2) healthy adults aged between 18 and 59 years. Study enrollment began on April 12, 2020. The interim analysis was conducted on June 16, 2020, and updated on July 27, 2020. MAIN OUTCOMES AND MEASURES The primary safety outcome was the combined adverse reactions 7 days after each injection, and the primary immunogenicity outcome was neutralizing antibody response 14 days after the whole-course vaccination, which was measured by a 50% plaque reduction neutralization test against live severe acute respiratory syndrome coronavirus 2 (SARS-CoV-2). RESULTS Among 320 patients who were randomized (mean age, 42.8 years; 200 women [62.5%]), all completed the trial up to 28 days after the whole-course vaccination. The 7-day adverse reactions occurred in 3 (12.5%), 5 (20.8%), 4 (16.7%), and 6 (25.0%) patients in the alum only, low-dose, medium-dose, and high-dose groups, respectively, in the phase 1 trial; and in 5 (6.0%) and 4 (14.3%) patients who received injections on days 0 and 14 for vaccine and alum only, and 16 (19.0%) and 5 (17.9%) patients who received injections on days 0 and 21 for vaccine and alum only, respectively, in the phase 2 trial. The most common adverse reaction was injection site pain, followed by fever, which were mild and self-limiting; no serious adverse reactions were noted. The geometric mean titers of neutralizing antibodies in the low-, medium-, and high-dose groups at day 14 after 3 injections were 316 (95% CI, 218-457), 206 (95% CI, 123-343), and 297 (95% CI, 208-424), respectively, in the phase 1 trial, and were 121 (95% CI, 95-154) and 247 (95% CI, 176-345) at day 14 after 2 injections in participants receiving vaccine on days 0 and 14 and on days 0 and 21, respectively, in the phase 2 trial. There were no detectable antibody responses in all alum-only groups. CONCLUSIONS AND RELEVANCE In this interim report of the phase 1 and phase 2 trials of an inactivated COVID-19 vaccine, patients had a low rate of adverse reactions and demonstrated immunogenicity; the study is ongoing. Efficacy and longer-term adverse event assessment will require phase 3 trials.

Decline of SARS-CoV-2-specific IgG, IgM and IgA in convalescent COVID-19 patients within 100 days after hospital discharge

“…One way is to seek immunogens and adjuvants that elicit very strong immune responses such as virus-specific IgG induction, which can be easily monitored. For example, a recent clinical trial showed that an experimental vaccine using inactivated SARS-CoV-2 viruses with alum as the adjuvant only elicited comparable, but not much higher virus-specific IgG production than what we and others observed in hospitalized COVID-19 patients (Xia et al, 2020). Using more potent immunogens and adjuvants to enhance immune responses for stronger SARS-CoV-2 IgG production will be an important early indication for effective development of SARS-CoV-2 vaccines that are highly potent and long-lasting.…”

A systematic review of SARS-CoV-2 vaccine candidates

“…43 Phase 2 trial results of the inactivated SARS-CoV-2 vaccine, constructed by Wuhan Institute of Biological Products and Sinopharm, reported that the geometric mean titers (GMT) of NAbs were 121 and 247 at day 14 after 2 injections in participants receiving vaccine on days 0 and 14 and on days 0 and 21, respectively, displaying only transient and self-limiting adverse reactions. 44 Viral RNA Fig. 1 The immune responses induced by SARS-CoV-2.…”

Frontiers in the COVID-19 vaccines development

“…The Ad5-vectored COVID-19 vaccine at 5 × 10 10 viral particles was safe, and induced significant immune responses in the majority of recipients after a single immunization (NCT04341389) [12]. Analysis of 2 randomized phase 1 and phase 2 clinical trials of inactivated vaccine showed that patients had a low rate of adverse reactions and demonstrated immunogenicity (ChiCTR2000031809) [13]. Phase 1/2 single-blind, randomised controlled trial with adenovirus vaccine that expresses the spike protein of SARS-CoV-2 in chimpanzee (ChAdOx1 nCoV-19) showed an acceptable safety profile, and homologous boosting increased antibody responses [14].…”