The recent resurgence of respiratory infections following the COVID-19 pandemic is a topic of great interest, with the prevalence of viral infections such as influenza and respiratory syncytial virus (RSV) on the rise around the globe.1 With COVID-19 still spreading rapidly in many countries,2 the collision of these viruses has been termed a ‘tripledemic’.3 The incidence of bacterial infections such as Streptococcus pneumoniae and group A Streptococcus have also been increasing.4
Whilst the mechanisms behind the rising incidence of these infections are unknown, current thought amongst experts are around the concepts of immunity debt versus immunity theft.5
IMMUNITY DEBT
Implications of COVID-19 lockdowns
The prevalence of infectious diseases such as influenza and RSV decreased significantly during lockdowns,7 with a 93.4% reduction in RSV detection during winter 2020 in Australia.4 Researchers accurately predicted there would be a rise in viral infections following the NPIs imposed during the COVID-19 pandemic,8 with staggering surges in respiratory tract infections (RTIs) across the globe following the lifting of lockdowns in 2021.4,9,10 In 2022, compared to 2019, Germany saw a four-fold increase in the number of RTIs,9 with prevalence continuing to rise across Europe, with higher levels of fever and cough this past winter.11 Interestingly, there also appears to be a seasonal shift, with statistical data showing that the number of infections and hospital admissions post-pandemic were similar or even greater outside of the typical winter peaks,4 making immune health a consideration all year.
IMMUNITY THEFT
Immune system dysregulation
One of the most concerning long-term impacts of COVID-19 is the potential immune dysregulation that can persist after infection.13 Multiple studies have identified protein and genetic material from SARS-CoV-2 persisting in the body for over one year following contraction of COVID-19.13
Viral persistence may occur following acute infection if a virus is not completely cleared allowing for the continued viral replication and viral protein production to persist in tissues.13 These viral proteins are then released into circulation, interfering with immune responses, dysregulating the immune system, promoting inflammation, and activating latent viruses.13 Viral persistence can damage tissues by altering the differentiation of virus-specific T and B cells over time.13 A study demonstrated that immunological dysfunction persisted in patients with long COVID for 8 months after infection, with these patients demonstrating persistently highly activated innate immune cells and reduced naive T and B cells following infection.14
Remarkably, viral proteins have been found in tissues all over the body, including the reproductive system, cardiovascular system, brain, muscles, eyes, and lung tissue.15 Viral persistence has also been demonstrated with other viruses, such as Ebola virus, which can linger in tissues and cause chronic symptoms and new outbreaks.16
SUPPORTING IMMUNE SYSTEM HEALTH
Nutrients and herbal medicines
Certain nutrients and herbal medicines can support the regulation of immune activity, providing protection from infections, relief of common symptoms, and accelerate recovery.
Key nutrients to enhance immune system health include zinc, vitamins C and D, probiotics, and quercetin, with specific therapeutic dosages recommended for protection against respiratory viruses (see Table 1).21 Together, these nutrients play a key role in immune system defence and restoration (see Table 2).21
Lifestyle
Evidence clearly demonstrates the importance of regular physical activity, adequate sleep, and effective stress management for optimal immune system health. Lack of movement, poor sleep, and chronic stress can hinder immune function, promote inflammation, and increase the risk of infection from respiratory viruses.22
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References
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