Impact of inactivated vaccines on decrease of viral RNA levels in individuals with the SARS-CoV-2 Omicron (BA.2) variant: A retrospective cohort study in Shanghai, China

Peng Yang; Bianli Dang; Wen Kang; Xiaofeng Li; Tianping Wang; Ruijuan Li; Meijuan Peng; Yushen Liu; Linxu Wang; Yan Cheng; Suhuai Yu; Min Wei; Han Gao; Wenzhen Kang; Lei Shang

doi:10.3389/fpubh.2023.1107343

Impact of inactivated vaccines on decrease of viral RNA levels in individuals with the SARS-CoV-2 Omicron (BA.2) variant: A retrospective cohort study in Shanghai, China

Front Public Health. 2023 Mar 7:11:1107343. doi: 10.3389/fpubh.2023.1107343. eCollection 2023.

Authors

Peng Yang¹, Bianli Dang², Wen Kang², Xiaofeng Li², Tianping Wang², Ruijuan Li², Meijuan Peng², Yushen Liu², Linxu Wang², Yan Cheng², Suhuai Yu², Min Wei², Han Gao³, Wenzhen Kang², Lei Shang¹

Affiliations

¹ Department of Health Statistics, Ministry of Education Key Lab of Hazard Assessment and Control in Special Operational Environment, School of Public Health, Fourth Military Medical University, Xi'an, China.
² Department of Infectious Diseases, The Second Affiliated Hospital, Fourth Military Medical University, Xi'an, China.
³ The Third Regiment, Basic Medical Science Academy, Fourth Military Medical University, Xi'an, China.

Abstract

Background: SARS-CoV-2 Omicron (BA.2) has stronger infectivity and more vaccine breakthrough capability than previous variants. Few studies have examined the impact of inactivated vaccines on the decrease of viral RNA levels in individuals with the Omicron variant, based on individuals' continuous daily cycle threshold (Ct) values and associated medical information from the infection to hospital discharge on a large population.

Methods: We extracted 39,811 individuals from 174,371 Omicron-infected individuals according to data inclusion and exclusion criteria. We performed the survival data analysis and Generalized Estimating Equation to calculate the adjusted relative risk (aRR) to assess the effect of inactivated vaccines on the decrease of viral RNA levels.

Results: Negative conversion was achieved in 54.7 and 94.3% of all infected individuals after one and 2 weeks, respectively. aRRs were shown weak effects on turning negative associated with vaccinations in asymptomatic infections and a little effect in mild diseases. Vaccinations had a protective effect on persistent positivity over 2 and 3 weeks. aRRs, attributed to full and booster vaccinations, were both around 0.7 and had no statistical significance in asymptomatic infections, but were both around 0.6 with statistical significance in mild diseases, respectively. Trends of viral RNA levels among vaccination groups were not significant in asymptomatic infections, but were significant between unvaccinated group and three vaccination groups in mild diseases.

Conclusion: Inactivated vaccines accelerate the decrease of viral RNA levels in asymptomatic and mild Omicron-infected individuals. Vaccinated individuals have lower viral RNA levels, faster negative conversion, and fewer persisting positive proportions than unvaccinated individuals. The effects are more evident and significant in mild diseases than in asymptomatic infections.

Keywords: COVID-19; Omicron; SARS-CoV-2; inactivated vaccines; viral RNA levels.

Publication types

Research Support, Non-U.S. Gov't

MeSH terms

Asymptomatic Infections*
COVID-19* / epidemiology
COVID-19* / prevention & control
China / epidemiology
Humans
RNA, Viral
Retrospective Studies
SARS-CoV-2
Vaccines, Inactivated

Substances

Vaccines, Inactivated
RNA, Viral

Supplementary concepts

SARS-CoV-2 variants

Grants and funding

This work is supported by the National Natural Science Foundation of China (82173627), Logistics Science and Technology Youth Cultivation Program (20QNPY047), Medicine Enhancement Programme of FMMU (2020SWAQ10), and Key R & D Program of Shaanxi Province (2023-YBSF-546 and 2021SF-345).