Safety, tolerability, and immunogenicity of an aerosolised adenovirus type-5 vector-based COVID-19 vaccine (Ad5-nCoV) in adults: preliminary report of an open-label and randomised phase 1 clinical trial

Abstract

Background: SARS-CoV-2 has caused millions of deaths, and, since Aug 11, 2020, 20 intramuscular COVID-19 vaccines have been approved for use. We aimed to evaluate the safety and immunogenicity of an aerosolised adenovirus type-5 vector-based COVID-19 vaccine (Ad5-nCoV) in adults without COVID-19 from China.

Method: This was a randomised, single-centre, open-label, phase 1 trial done in Zhongnan Hospital (Wuhan, China), to evaluate the safety and immunogenicity of the Ad5-nCoV vaccine by aerosol inhalation in adults (≥18 years) seronegative for SARS-CoV-2. Breastfeeding or pregnant women and people with major chronic illnesses or history of allergies were excluded. Participants were enrolled and randomly assigned (1:1:1:1:1) into five groups to be vaccinated via intramuscular injection, aerosol inhalation, or both. Randomisation was stratified by sex and age (18-55 years or ≥56 years) using computer-generated randomisation sequences (block sizes of five). Only laboratory staff were masked to group assignment. The participants in the two aerosol groups received an initial high dose (2 × 10¹⁰ viral particles; HDmu group) or low dose (1 × 10¹⁰ viral particles; LDmu group) of Ad5-nCoV vaccine on day 0, followed by a booster on day 28. The mixed vaccination group received an initial intramuscular (5 × 10¹⁰ viral particles) vaccine on day 0, followed by an aerosolised booster (2 × 10¹⁰ viral particles) vaccine on day 28 (MIX group). The intramuscular groups received one dose (5 × 10¹⁰ viral particles; 1Dim group) or two doses (10 × 10¹⁰ viral particles; 2Dim group) of Ad5-nCoV on day 0. The primary safety outcome was adverse events 7 days after each vaccination, and the primary immunogenicity outcome was anti-SARS-CoV-2 spike receptor IgG antibody and SARS-CoV-2 neutralising antibody geometric mean titres at day 28 after last vaccination. This trial is registered with ClinicalTrials.gov, number NCT04552366.

Findings: Between Sept 28, 2020, and Sept 30, 2020, 230 individuals were screened for inclusion, of whom 130 (56%) participants were enrolled into the trial and randomly assigned into one of the five groups (26 participants per group). Within 7 days after vaccination, adverse events occurred in 18 (69%) in the HDmu group, 19 (73%) in the LDmu group, 19 (73%) in the MIX group, 19 (73%) in the 1Dim group, and 15 (58%) in the 2Dim group. The most common adverse events reported 7 days after the first or booster vaccine were fever (62 [48%] of 130 participants), fatigue (40 [31%] participants), and headache (46 [35%] participants). More adverse events were reported in participants who received intramuscular vaccination, including participants in the MIX group (49 [63%] of 78 participants), than those who received aerosol vaccine (13 [25%] of 52 participants) after the first vaccine vaccination. No serious adverse events were noted within 56 days after the first vaccine. At days 28 after last vaccination, geometric mean titres of SARS-CoV-2 neutralising antibody was 107 (95% CI 47-245) in the HDmu group, 105 (47-232) in the LDmu group, 396 (207-758) in the MIX group, 95 (61-147) in the 1Dim group, and 180 (113-288) in the 2Dim group. The geometric mean concentrations of receptor binding domain-binding IgG was 261 EU/mL (95% CI 121-563) in the HDmu group, 289 EU/mL (138-606) in the LDmu group, 2013 EU/mL (1180-3435) in the MIX group, 915 EU/mL (588-1423) in the 1Dim group, and 1190 EU/mL (776-1824) in the 2Dim group.

Interpretation: Aerosolised Ad5-nCoV is well tolerated, and two doses of aerosolised Ad5-nCoV elicited neutralising antibody responses, similar to one dose of intramuscular injection. An aerosolised booster vaccination at 28 days after first intramuscular injection induced strong IgG and neutralising antibody responses. The efficacy and cost-effectiveness of aerosol vaccination should be evaluated in future studies.

Funding: National Key Research and Development Programme of China and National Science and Technology Major Project.

Translation: For the Chinese translation of the Summary see Supplementary Material.

Figure 1

Trial profile 1Dim=low-dose intramuscular injection. 2Dim=high-dose intramuscular injection. Ad5-nCoV=recombinant adenovirus type 5 carrying full-length SARS-CoV-2 spike gene. HDmu=high-dose aerosol vaccine. LDmu=low-dose aerosol vaccine. MIX=intramuscular and aerosol vaccine.

Figure 2

Solicited adverse events following Ad5-nCoV vaccination Solicited adverse events reported within 7 days after prime (A) and booster (B) vaccination with Ad5-nCoV. The severity of solicited adverse events was graded as grade 1, grade 2, grade 3, or grade 4 according to the scale issued by the China National Medical Products of Administration (appendix 2 p 7). Participants in the 1Dim and 2Dim groups did not receive a booster vaccine. 1Dim=low-dose intramuscular injection. 2Dim=high-dose intramuscular injection. Ad5-nCoV=recombinant adenovirus type 5 carrying full-length SARS-CoV-2 spike gene. HDmu=high-dose aerosol vaccine. LDmu=low-dose aerosol vaccine. MIX=intramuscular and aerosol vaccine.

Figure 3

Sera IgG, IgA, and neutralising antibody response following Ad5-nCoV vaccination Spike RBD-binding IgG (A) and IgA concentrations (B) by ELISA and SARS-CoV-2 neutralising antibody (C) following Ad5-nCoV vaccination. All groups received the first vaccine on day 0; the LDmu, HDmu, and MIX group received a booster vaccine on day 28. Each data point represents a serum sample. The error bars are geometric mean with 95% CI. Geometric mean concentration and geometric mean titre are reported. Dashed lines shows the lower limit of quantification. 1Dim=low-dose intramuscular injection. 2Dim=high-dose intramuscular injection. Ad5-nCoV=recombinant adenovirus type 5 carrying full-length SARS-CoV-2 spike gene. HDmu=high-dose aerosol vaccine. LDmu=low-dose aerosol vaccine. MIX=intramuscular and aerosol vaccine. RBD=receptor binding domain.

Figure 4

SARS-CoV-2 spike protein-specific cellular immune response following Ad5-nCoV vaccination (A) SARS-CoV-2 spike-specific IFN-γ were detected by enzyme-linked immunospot following Ad5-nCoV vaccination. Each data point represents the mean number of spots from triplicate wells for one participant, after subtraction of the unstimulated control. Error bars show the interquartile range. Dashed line shows the lower limit of quantification. All groups received the first vaccine on day 0; the LDmu, HDmu, and MIX group received a booster vaccine on day 28. (B) Spike protein-specific IFN-γ, IL-2, IL-4, and IL-13 responses in memory CD4 T cells, measured at day 0 and day 14. (C) Spike protein-specific IFN-γ, IL-2, IL-4, and IL-13 responses in memory CD8 T cells, measured at day 0 and day 14. Responses were detected by intracellular cytokine staining; each data point represents the mean percentage of indicated cytokine in T cell subsets from duplicate tests, after subtraction of the unstimulated control. 1Dim=low-dose intramuscular injection. 2Dim=high-dose intramuscular injection. Ad5-nCoV=recombinant adenovirus type 5 carrying full-length SARS-CoV-2 spike gene. HDmu=high-dose aerosol vaccine. IFN=interferon. LDmu=low-dose aerosol vaccine. MIX=intramuscular and aerosol vaccine.