tetano
Editor, Senior Moderator
Int J Infect Dis
. 2025 Nov 16:108221.
doi: 10.1016/j.ijid.2025.108221. Online ahead of print. Short-Term Risks of Influenza and COVID-19 Following Influenza Infection: A Self-Controlled Case Series Study
Chao Wang[SUP] 1 [/SUP], Yanlin Gao[SUP] 2 [/SUP], Wei Li[SUP] 2 [/SUP], Jing Du[SUP] 2 [/SUP], Xiao Hu[SUP] 3 [/SUP], Jiaze Li[SUP] 3 [/SUP], Yang Liu[SUP] 3 [/SUP], Yunping Shi[SUP] 3 [/SUP], Ying Zhou[SUP] 3 [/SUP], Gang Li[SUP] 4 [/SUP]
Affiliations
Objectives: Given the inconsistent existing evidence on viral interference between influenza and COVID-19, this study aimed to investigate the short-term risks of influenza reinfection and COVID-19 infections following an initial influenza episode, in the context of cocirculating influenza and SARS-CoV-2 viruses.
Methods: Using a seasonally adjusted self-controlled case series (SCCS) design, we analysed surveillance data from Beijing, China, collected between February 2023 and June 2025. The study included individuals infected with influenza who subsequently experienced either influenza reinfection or COVID-19 within 18 months after the initial influenza infection.
Results: The study comprised 17,859 individuals with influenza followed by COVID-19 (flu-COVID) and 34,291 with sequential influenza infections (flu-flu). Influenza infection was associated with a transient increase in the risk of COVID-19 within 6 months (IRR = 1.48, 95% CI: 1.39-1.59). In contrast, the risk of influenza reinfection was significantly reduced during the same period (IRR = 0.43, 95% CI: 0.39-0.49). Although risk modulation varied across demographic subgroups, results from subgroup and sensitivity analyses were largely consistent.
Conclusions: Influenza infection may temporarily increase susceptibility to COVID-19 while reducing the risk of influenza reinfection. These findings highlight the importance of targeted surveillance and preventive strategies during influenza peaks to mitigate subsequent COVID-19 burden.
Keywords: COVID-19; Influenza; Self-Controlled Case Series Study; Short-term risk.
. 2025 Nov 16:108221.
doi: 10.1016/j.ijid.2025.108221. Online ahead of print. Short-Term Risks of Influenza and COVID-19 Following Influenza Infection: A Self-Controlled Case Series Study
Chao Wang[SUP] 1 [/SUP], Yanlin Gao[SUP] 2 [/SUP], Wei Li[SUP] 2 [/SUP], Jing Du[SUP] 2 [/SUP], Xiao Hu[SUP] 3 [/SUP], Jiaze Li[SUP] 3 [/SUP], Yang Liu[SUP] 3 [/SUP], Yunping Shi[SUP] 3 [/SUP], Ying Zhou[SUP] 3 [/SUP], Gang Li[SUP] 4 [/SUP]
Affiliations
- PMID: 41253202
- DOI: 10.1016/j.ijid.2025.108221
Objectives: Given the inconsistent existing evidence on viral interference between influenza and COVID-19, this study aimed to investigate the short-term risks of influenza reinfection and COVID-19 infections following an initial influenza episode, in the context of cocirculating influenza and SARS-CoV-2 viruses.
Methods: Using a seasonally adjusted self-controlled case series (SCCS) design, we analysed surveillance data from Beijing, China, collected between February 2023 and June 2025. The study included individuals infected with influenza who subsequently experienced either influenza reinfection or COVID-19 within 18 months after the initial influenza infection.
Results: The study comprised 17,859 individuals with influenza followed by COVID-19 (flu-COVID) and 34,291 with sequential influenza infections (flu-flu). Influenza infection was associated with a transient increase in the risk of COVID-19 within 6 months (IRR = 1.48, 95% CI: 1.39-1.59). In contrast, the risk of influenza reinfection was significantly reduced during the same period (IRR = 0.43, 95% CI: 0.39-0.49). Although risk modulation varied across demographic subgroups, results from subgroup and sensitivity analyses were largely consistent.
Conclusions: Influenza infection may temporarily increase susceptibility to COVID-19 while reducing the risk of influenza reinfection. These findings highlight the importance of targeted surveillance and preventive strategies during influenza peaks to mitigate subsequent COVID-19 burden.
Keywords: COVID-19; Influenza; Self-Controlled Case Series Study; Short-term risk.