Summary:

There is speculation that the off-season surge in pediatric respiratory infections is due to "immunity debt" caused by nonpharmaceutical interventions (NPIs) implemented during the COVID-19 pandemic. However, there is no statistical or published evidence to support this concept. Early exposure to respiratory viruses does not confer long-term protection, and infants under 6 months of age are particularly susceptible to severe respiratory infections. The impact of NPIs on the pediatric population is limited, as the strictest measures did not affect infants and young children. Post-COVID-19 immune dysregulation can contribute to susceptibility to respiratory infections. It is important to note that most children have been infected with COVID-19, and the long-term effects of the virus on the immune system are still being studied. Many viruses, including measles, can cause persistent immune dysregulation, secondary infections, autoimmunity, and malignancies. Public health measures, including NPIs and vaccines, are crucial in reducing hospitalizations and mortality. Skepticism around these measures undermines efforts to address the current healthcare crisis and build long-term solutions.

Takeaways:

🔬 There is no evidence to support the concept of "immunity debt" causing the surge in pediatric respiratory infections.

🤧 Early exposure to respiratory viruses does not provide long-term protection.

👶 Infants under 6 months of age are particularly susceptible to severe respiratory infections.

⚠️ The impact of NPIs on the pediatric population is limited, as the strictest measures did not affect infants and young children.

🩺 Post-COVID-19 immune dysregulation can contribute to susceptibility to respiratory infections.

💉 Most children have been infected with COVID-19, and the long-term effects of the virus on the immune system are still being studied.

🦠 Many viruses, including measles, can cause persistent immune dysregulation and other negative effects.

🏥 Public health measures, including NPIs and vaccines, are crucial in reducing hospitalizations and mortality.

⛔️ Skepticism around public health measures undermines efforts to address the current healthcare crisis.

🔍 Further research is needed to fully understand the impact of COVID-19 on the immune system and respiratory infections in children.

Off-Season Surge in Pediatric Respiratory Infections and Immunity Debt: Debunking the Myth

Introduction

An off-season surge in hospital admissions due to RSV, influenza and other viral infections in the pediatric population commonly has been attributed to immunity debt. Introduced in 2021, the term suggests that nonpharmaceutical interventions (NPIs) instituted to reduce exposure to SARS-CoV-2 led to a reduction in other respiratory viruses and resulted in decreased immunity, rendering a large proportion of the pediatric population susceptible to future infections.

Lack of Evidence

Let us be clear: There is no statistical or published evidence to support this concept.

Early Respiratory Infections Provide No Long-term Benefits

The term immunity debt purports that early exposure to respiratory viruses protects against future infections. On the contrary, there is no benefit or evidence of harm from early respiratory infections such as RSV. In fact, antibodies gained from early RSV infections dissipate over time and ongoing immunity requires recurrent seasonal exposures.

Severity of RSV in Infants

RSV in infants under 6 months of age can be particularly severe owing to an immature immune system and smaller airways. RSV is a major cause of lower respiratory tract infections and hospitalizations in the pediatric population.

COVID-19 Impact on Immune System

Numerous studies have shown that SARS-CoV-2 causes immune dysregulation both during the acute phase and after recovery. Post-COVID-19 immune dysregulation can cause reactivation of latent infections. One study showed persistent T-cell abnormalities in convalescent COVID-19 patients three months after initial infection. Another study revealed evidence of immunodeficiency caused by downregulation of CD19 expression on B cells in recovered COVID-19 patients.

Prevalence of COVID-19 Infection in Children

Most children have been infected by SARS-CoV-2, particularly the Omicron variant. The Centres for Disease Control and Prevention estimated that by February 2022, 75 per cent of children had been infected by COVID-19. Furthermore, according to the Public Health Agency of Canada, only 1 per cent of the pediatric population under the age 5 have received a full primary series of the COVID-19 vaccine. As such, it is plausible that children are experiencing immune system dysfunction as a long-term effect of COVID-19 infection, making them more susceptible to severe respiratory infections.

Many viruses are known to also cause persistent immune dysregulation, secondary infections, autoimmunity and malignancies.

While data demonstrating the correlation between COVID-19 infection and subsequent respiratory infections from other viruses such as RSV is not available, the concept of post-infectious immune dysfunction is not new. Many viruses, including Epstein Barr Virus, hepatitis C and measles are known to also cause persistent immune dysregulation, secondary infections, autoimmunity and malignancies. Although measles is a vaccine preventable illness, rates of measles vaccination have been declining, in part due to misinformation on social media. This has long-term consequences. The measles virus can non-specifically infect up to 70 per cent of immune memory cells, including B cells, T cells, and plasma cells in the lymphoid tissue and peripheral blood, erasing existing immunity to previously acquired infections. As a result, measles related mortality is predominantly due to increase in susceptibility to bacterial or viral infections.

Importance of Public Health Measures and Vaccines

Public health measures including NPIs and vaccines have played an important role in reducing hospitalizations, morbidity and mortality from COVID-19 infection. This is due in part to following the precautionary principle of using a proactive approach to risk mitigation in the face of serious and irreversible threats to the environment amid scientific uncertainty. This is critical when confronted with novel pathogens such as SARS-CoV-2. Even at the height of the pandemic, however, these protective measures were criticized, gaining traction on social media. Similarly, the term immunity debt is now being exploited to provide negative connotation to public health measures that were used to minimize health-care pressures, morbidity and death during the pandemic.

Long-Term Strategies and Unknowns

Skepticism around public health measures has dire implications now amid a health-care crisis. By creating a false narrative in which the blame is placed on NPIs, the focus is shifted away from building long-term solutions such as improving ventilation in public spaces, addressing health-care resource and staffing crises, ensuring access to antipyretics, creating variant-proof vaccine strategies and promoting vaccine uptake in the general population.

Conclusion

Superficially, immunity debt is an attractive concept. However, there is little evidence for immunity debt as an explanation for the resurgence in pediatric respiratory infections. The real cause is likely multifactorial. For now, it may be better explained by post-COVID-19 immune dysregulation. We are only beginning to understand the true impact of COVID-19, and data in the coming months and years will elucidate some of the current unknowns.