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Induction of trained immunity by influenza vaccination - impact on COVID-19.

PLoS pathogens

Authors: Priya A Debisarun, Katharina L Gössling, Ozlem Bulut, Gizem Kilic, Martijn Zoodsma, Zhaoli Liu, Marina Oldenburg, Nadine Rüchel, Bowen Zhang, Cheng-Jian Xu, Patrick Struycken, Valerie A C M Koeken, Jorge Domínguez-Andrés, Simone J C F M Moorlag, Esther Taks, Philipp N Ostermann, Lisa Müller, Heiner Schaal, Ortwin Adams, Arndt Borkhardt, Jaap Ten Oever, Reinout van Crevel, Yang Li, Mihai G Netea

Non-specific protective effects of certain vaccines have been reported, and long-term boosting of innate immunity, termed trained immunity, has been proposed as one of the mechanisms mediating these effects. Several epidemiological studies suggested cross-protection between influenza vaccination and COVID-19. In a large academic Dutch hospital, we found that SARS-CoV-2 infection was less common among employees who had received a previous influenza vaccination: relative risk reductions of 37% and 49% were observed following influenza vaccination during the first and second COVID-19 waves, respectively. The quadrivalent inactivated influenza vaccine induced a trained immunity program that boosted innate immune responses against various viral stimuli and fine-tuned the anti-SARS-CoV-2 response, which may result in better protection against COVID-19. Influenza vaccination led to transcriptional reprogramming of monocytes and reduced systemic inflammation. These epidemiological and immunological data argue for potential benefits of influenza vaccination against COVID-19, and future randomized trials are warranted to test this possibility.

PMID: 34695164

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