J Korean Med Sci.  2022 Jul;37(27):e210. 10.3346/jkms.2022.37.e210.

Immunogenicity and Reactogenicity of Ad26.COV2.S in Korean Adults: A Prospective Cohort Study

• Hyun H
• Choi MJ
• Heo JY
• Seo YB
• Nham E
• Yoon JG
• Seong H
• Noh JY
• Cheong HJ
• Kim WJ
• Choi JY
• Lee YJ
• Lee HW
• Kim SS
• Kim B
• Song JY

• KMID: 2531248
• DOI: http://doi.org/10.3346/jkms.2022.37.e210

Abstract

Background
As the coronavirus disease 2019 (COVID-19) pandemic continues, there are concerns regarding waning immunity and the emergence of viral variants. The immunogenicity of Ad26.COV2.S against wild-type (WT) and variants of the severe acute respiratory syndrome coronavirus 2 (SARS-CoV-2) needs to be evaluated. Method: This prospective cohort study was conducted between June 2021 and January 2022 at two university hospitals in South Korea. Healthy adults who were scheduled to be vaccinated with Ad26.COV2.S were enrolled in this study. The main outcomes included anti-spike (S) IgG antibody and neutralizing antibody responses, S-specific T-cell responses (interferon-γ enzyme-linked immunospot assay), solicited adverse events (AEs), and serious AEs.
Results
Fifty participants aged ≥ 19 years were included in the study. Geometric mean titers (GMTs) of anti-S IgG were 0.4 U/mL at baseline, 5.2 ± 3.0 U/mL at 3–4 weeks, 55.7 ± 2.4 U/mL at 5–8 weeks, and 81.3 ± 2.5 U/mL at 10–12 weeks after vaccination. GMTs of 50% neutralizing dilution (ND50) against WT SARS-CoV-2 were 164.6 ± 4.6 at 3-4 weeks, 313.9 ± 3.6 at 5–8 weeks, and 124.4 ± 2.6 at 10–12 weeks after vaccination. As for the S-specific T-cell responses, the median number of spot-forming units/10 6 peripheral blood mononuclear cell was 25.0 (5.0–29.2) at baseline, 60.0 (23.3–178.3) at 5-8 weeks, and 35.0 (13.3–71.7) at 10–12 weeks after vaccination. Compared to WT SARS-CoV-2, ND50 against Delta and Omicron variants was attenuated by 3.6-fold and 8.2-fold, respectively. The most frequent AE was injection site pain (82%), followed by myalgia (80%), fatigue (70%), and fever (50%). Most AEs were grade 1–2, and resolved within two days.
Conclusion
Single-dose Ad26.COV2.S was safe and immunogenic. NAb titer and S-specific T-cell immunity peak at 5–8 weeks and rather decrease at 10–12 weeks after vaccination. Cross-reactive neutralizing activity against the Omicron variant was negligible.

Keyword

SARS-CoV-2; COVID-19; Vaccines; Adenovirus Vector; Humoral Immunity; Cellular Immunity; Adverse Events

Figure

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  Fig. 1 Study flowchart.IgG = immunoglobulin G, S = spike.

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  Fig. 2 Immunogenicity after Ad26.COV2.S vaccination. (A) Titer of anti-Spike (S) anti-SARS-CoV-2 spike protein IgG, (B) 50% neutralization dose (ND50), (C) median of S-specific T-cell responses measured by IFN-γ ELISpot assay. The black bar represents geometric mean titer with 95% confidence intervals.ELISA = enzyme-linked immunosorbent assay, IgG = immunoglobulin G, SFU = spot forming unit, IFN-γ = interferon-γ, ELISpot = enzyme-linked immuneSpot.

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  Fig. 3 Neutralization assay against Delta and Omicron variants. The black bar represents geometric mean titer with 95% confidence intervals.ND50 = 50% neutralization dilution, WT = wild-type.

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  Fig. 4 Incidence, severity, and duration of adverse events after Ad26.COV2.S.

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