Effectiveness of primary series, first, and second booster vaccination of monovalent mRNA COVID-19 vaccines against symptomatic SARS-CoV-2 infections and severe diseases during the SARS-CoV-2 omicron BA.5 epidemic in Japan: vaccine effectiveness real-time surveillance for SARS-CoV-2 (VERSUS)

ABSTRACT

Background

This study aimed to evaluate VE of primary, first, and second booster ancestral-strain monovalent mRNA COVID-19 vaccination against symptomatic infections and severe diseases in Japan.

Methods

We conducted a test-negative case-control study. We included medically attended episodes and hospitalizations involving individuals aged $\ge$16 with signs and symptoms from July to November 2022, when Omicron BA.5 was dominant nationwide. To evaluate VE, we calculated adjusted ORs of vaccination among test-positive versus test-negative individuals using a mixed-effects logistic regression.

Results

For VE against symptomatic infections among individuals aged 16 to 59, VE of primary vaccination at > 180 days was 26.1% (95% CI: 10.6–38.8%); VE of the first booster was 58.5% (48.4–66.7%) at $\le$90 days, decreasing to 41.1% (29.5–50.8%) at 91 to 180 days. For individuals aged $\ge$60, VE of the first booster was 42.8% (1.7–66.7%) at $\le$90 days, dropping to 15.4% (−25.9–43.2%) at 91 to 180 days, and then increasing to 44.0% (16.4–62.5%) after the second booster. For VE against severe diseases, VE of the first and second booster was 77.3% (61.2–86.7%) at $\le$90 days and 55.9% (23.4–74.6%) afterward.

Conclusion

mRNA booster vaccination provided moderate protection against symptomatic infections and high-level protection against severe diseases during the BA.5 epidemic in Japan.

KEYWORDS:

• BA.5
• COVID-19
• Japan
• SARS-CoV-2
• vaccine effectiveness
• monovalent

Acknowledgments

We are grateful to medical staff of the participating hospitals and clinics. We thank Yukie Kozone, Rina Kubo, Yumi Araki, Rina Shiramizu (Institute of Tropical Medicine, Nagasaki University), and Daichi Hatahara (Nagasaki University) for their assistance.

Declaration of interest

H Maeda reports lecture and consulting fees from Moderna Inc and participating in Pfizer Inc-funded research outside this work. AI reports grants from Takeda Pharmaceutical Inc, consulting fees from Pfizer Inc and Astra Zeneca Inc, and lecture fees from Takeda Pharmaceutical Inc, Shionogi Inc, Janssen Pharma Inc, and Moderna Inc outside this work. M Terada reports lecture fees from Astra Zeneca outside this work. H Inoue reports participating in research funded by Pfizer Inc, research funded by GENOVA Inc, research funded by Astra Zeneca Inc, and research funded by FUJIFILM Toyama Chemical CO., Ltd. outside this work. T Hayakawa reports stock ownership of Takeda Pharmaceutical Inc. and Daiichi Sankyo Healthcare Co., Ltd. K Morimoto reports grants from Pfizer Inc, consulting fees from Moderna Inc, and lecture fees from MSD outside this work. The authors have no other relevant affiliations or financial involvement with any organization or entity with a financial interest in or financial conflict with the subject matter or material discussed in the manuscript apart from those disclosed.

Reviewer disclosures

Peer reviewers on this manuscript have received honoraria for their review work. Peer reviewers on this manuscript have no other relevant financial or other relationships to disclose.

Abbreviations

Coronavirus disease 2019 (COVID-19); messenger RNA (mRNA); severe acute respiratory syndrome coronavirus 2 (SARS-CoV-2); polymerase chain reaction (PCR), loop-medical isothermal amplification (LAMP); nicking endonuclease amplification reaction (NEAR); transcription-mediated amplification (TMA); oxygen saturation (SpO₂); Institutional Review Board (IRB); confidence interval (CI).

Author contributions

HM, NS, AI, MI, MT, SM, MS, and KM conceived and designed the study. MI, MT, RO, NH, KN, HK, HI, HI, SM, YS, OK, IM, TM, RO, YH, TM, OT, ES, SA, SK, NA, YM, TH, TK, and YO collected and verified the data. HM and NS did the analysis and MS and YK supervised the analysis. AI performed the analysis separately from HM and NS. HM, NS, AI, MI, MT, SM, MS, and KM had full access to the data. HM and KM wrote the first draft of the manuscript, and all authors provided critical review and revision of the text and approved the final version for publication.

Supplementary material

Supplemental data for this article can be accessed online at https://doi.org/10.1080/14760584.2024.2310807.

Additional information

Funding

This work was supported by the Ministry of Health, Labour and Welfare [Grant number: 21HA2008 and 23HA2017].