The effect of influenza vaccination on trained immunity: impact on COVID-19

Abstract

Every year, influenza causes 290.000 to 650.000 deaths worldwide and vaccination is encouraged to prevent infection in high-risk individuals. Interestingly, cross-protective effects of vaccination against heterologous infections have been reported, and long-term boosting of innate immunity (also termed trained immunity) has been proposed as the underlying mechanism. Several epidemiological studies also suggested cross-protection between influenza vaccination and COVID-19 during the current pandemic. However, the mechanism behind such an effect is unknown. Using an established in-vitro model of trained immunity, we demonstrate that the quadrivalent inactivated influenza vaccine used in the Netherlands in the 2019-2020 influenza season can induce a trained immunity response, including an improvement of cytokine responses after stimulation of human immune cells with SARS-CoV-2. In addition, we found that SARS-CoV-2 infection was less common among Dutch hospital employees who had received influenza vaccination during the 2019/2020 winter season (RR = 0,61 (95% CI, 0.4585 - 0.8195, P = 0.001). In conclusion, a quadrivalent inactivated influenza vaccine can induce trained immunity responses against SARS-CoV-2, which may result in relative protection against COVID-19. These data, coupled with similar recent independent reports, argue for a beneficial effect of influenza vaccination against influenza as well as COVID-19, and suggests its effective deployment in the 2020-2021 influenza season to protect against both infections.

Association between influenza vaccination and hospitalisation or all-cause mortality in people with COVID-19: a retrospective cohort study

“…9 11-14 This trained immunity may confer non-specific protection against different pathogens, inducing upregulation of pattern recognition receptors and the secretion of proinflammatory cytokines through epigenetic and metabolic reprogramming. [11][12][13][14] Another proposed mechanism is a process called 'emergency Open access granulopoiesis'. 37 This is based on the recent observation that following BCG vaccination in newborns; for example, there is induction of the growth factor granulocyte colony-stimulating factor which, in turn, leads to the rapid production of neutrophils, resulting in additional protection from subsequent infection.…”

COVID-19 case management: The policy model in Morocco context

“…Furthermore, in vitro experiment, from multi European research collaboration, confirmed that quadrivalent inactivated influenza vaccine induces trained immunity responses against SARS-CoV-2 that enhance the COVID-19 protection[22]. Many previous studies demonstrated this vaccination benefice for pregnant women, and their newborns protected against influenza via passively acquired antibodies[23].…”

“…If negative, another immediate RT-qPCR will be done from nasopharynx specimen If the viral load percentage is estimated clinically (low) between 32% and 05% just one RT-qPCR from the Nasopharynx should be done. 1 st Cq between [16][17][18][19][20][21][22][23][24][25][26][27][28][29][30][31][32][33] then control test Cq stays between [16][17][18][19][20][21][22][23][24][25][26][27][28][29][30][31][32][33] (one week after) 1 st Cq between [16][17][18][19][20][21][22][23][24][25][26][27][28]…”

Absence of association between 2019–20 influenza vaccination and COVID-19: results of the European I-MOVE-COVID-19 primary care project, March–August 2020

“…Biologically, it is possible that a long-lasting non-specific of 2019-20 influenza vaccination could have had a general effect on (some) virus infections. 20 Also, an interaction with previous human coronavirus infection and 2019-20 influenza vaccination may result in an indirect effect on SARS-CoV-2 infection. 21 Replication studies and further studies on the effects of a recent influenza vaccination on COVID-19 risk will help better understand whether there is no effect or a small protective effect of influenza vaccination on COVID-19.…”