J Korean Med Sci.  2023 Apr;38(13):e103. 10.3346/jkms.2023.38.e103.

Effects of Omicron Infection and Changes in Serum Antibody Response to Wild-Type, Delta, and Omicron After a Booster Dose With BNT163b2 Vaccine in Korean Healthcare Workers

• Lim SH
• Kim HJ
• Kim SH
• Choi SH
• Kim B
• Kim JY
• Ji YS
• Kim T
• Choo EJ
• Jung JC
• Moon JE
• Kim CK
• Park SK
• Yun J

• KMID: 2541044
• DOI: http://doi.org/10.3346/jkms.2023.38.e103

Abstract

Background
Although the primary vaccine coverage rate for coronavirus disease 2019 (COVID-19) in South Korea has exceeded 80%, the coronavirus continues to spread, with reports of a rapid decline in vaccine effectiveness. South Korea is administering booster shots despite concerns about the effectiveness of the existing vaccine.
Methods
Neutralizing antibody inhibition scores were evaluated in two cohorts after the booster dose. For the first cohort, neutralizing activity against the wild-type, delta, and omicron variants after the booster dose was evaluated. For the second cohort, we assessed the difference in neutralizing activity between the omicron infected and uninfected groups after booster vaccination. We also compared the effectiveness and adverse events (AEs) between homologous and heterologous booster doses for BNT162b2 or ChAdOx1 vaccines.
Results
A total of 105 healthcare workers (HCWs) that were additionally vaccinated with BNT162b2 at Soonchunhyang University Bucheon Hospital were enrolled in this study. Significantly higher surrogate virus neutralization test (sVNT) inhibition (%) was observed for the wild-type and delta variants compared to sVNT (%) for the omicron after the booster dose (97%, 98% vs. 75%; P < 0.001). No significant difference in the neutralizing antibody inhibition score was found between variants in the BNT/BNT/BNT group (n = 48) and the ChA/ChA/BNT group (n = 57). Total AEs were not significantly different between the ChA/ ChA/BNT group (85.96%) and the BNT/BNT group (95.83%; P = 0.11). In the second cohort with 58 HCWs, markedly higher sVNT inhibition to omicron was observed in the omicroninfected group (95.13%) compared to the uninfected group (mean of 48.44%; P < 0.001) after four months of the booster dose. In 41 HCWs (39.0%) infected with the omicron variant, no difference in immunogenicity, AEs, or effectiveness between homogeneous and heterogeneous boosters was observed.
Conclusion
Booster vaccination with BNT162b2 was significantly less effective for the neutralizing antibody responses to omicron variant compared to the wild-type or delta variant in healthy population. Humoral immunogenicity was sustained significantly high after 4 months of booster vaccine in the infected population after booster vaccination. Further studies are needed to understand the characteristics of immunogenicity in these populations.

Keyword

Omicron Variant; Neutralizing Antibody; Breakthrough Infection; COVID-19

Figure

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  Fig. 1 Flowchart of the COVID-19 vaccine study in HCW cohorts at Soonchunhyang University Bucheon Hospital.COVID-19 = coronavirus disease 2019, HCW = healthcare worker, SARS-CoV-2 = severe acute respiratory syndrome coronavirus 2.

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  Fig. 2 Neutralization effectiveness of the wild-type, delta, and omicron variants after the booster dose. Neutralizing antibody level measured by percent inhibition of sVNT readings at (A) negative control (unvaccinated) and (B) 4 weeks after booster vaccination.sVNT = surrogate virus neutralization test.

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  Fig. 3 A daily number of SARS-CoV-2 infections according to the period from booster vaccination to breakthrough infection (A) and over time after booster vaccination (B).SARS-CoV-2 = severe acute respiratory syndrome coronavirus 2.

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  Fig. 4 The pattern changes in sVNT inhibition (%) scores between omicron-infected (A) and uninfected individuals (B). Subsequent titers were measured 127.31 ± 9.77 days after booster vaccination in both groups (n = 33, n = 25).sVNT = surrogate virus neutralization test, SARS-CoV-2 = severe acute respiratory syndrome coronavirus 2.

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  Fig. 5 Neutralizing antibody level measured by sVNT inhibition of omicron in four groups. Each of the four groups consists of uninfected or infected with omicrons in the BNT/BNT/BNT or ChA/ChA/BNT group, respectively. Sequent titers were measured 128.61 ± 9.15 days after booster vaccination. Group A: BNT/BNT/BNT group-noninfected COVID-19 (n = 14), Group B: BNT/BNT/BNT group-infected COVID-19 (n = 20), Group C: ChA/ChA/BNT group-noninfected COVID-19 (n = 11), and Group D: ChA/ChA/BNT group-infected COVID-19 (n = 13).sVNT = surrogate virus neutralization test, COVID-19 = coronavirus disease 2019.

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