Immune Fitness Plays Critical Role in Pandemic Preparedness

Most attempts to reduce the threat of coronavirus disease 2019 (COVID-19) have focused on developing vaccines and implementing non-pharmaceutical interventions such as lockdowns and social distancing restrictions to limit the transmission of the disease. However, scientists at the Institute of Pharmaceutical Sciences in Utrecht are exploring other ways to prepare for future pandemics. For example, by maintaining a healthy lifestyle, such as avoiding unhealthy foods and smoking and maintaining regular physical activity among the population, immune fitness can be as crucial in reducing the impact of a pandemic as functional medicine. The research is published in the Journal of Clinical Medicine.

Study: Preparing for a pandemic: the importance of an adequate immune form. Image Credit:

The studies

During the pandemic, two studies were designed and implemented in the Netherlands, testing variables identified by assessments of demographic and clinical data, including age, weight and underlying disease, and immune fitness (assessed by self-reported disease) for correlation with number and severity of COVID-19 symptoms.

Corona lockdown: how fit are you? (CLOFIT) took place first and consisted of an anonymous online survey with participants recruited through Facebook ads. These people could not be tested for COVID-19 because the study took place very early in the pandemic. The second study was the Corona Test Street Survey (COTEST)which took place at test centers and assessed similar variables using an in-person questionnaire.

In the CLOFIT study, which took place online during the first Dutch lockdown, a total of 1,415 participants were assessed, all between the ages of 18 and 94. 920 of these people reported at least one underlying chronic disease. Women tend to be younger than men and have a lower body mass index (BMI), but also have a lower level of immune fitness before (Immune fitness 2019) and during confinement (Immune fitness DL). Additionally, women have reported more and more severe COVID-19 symptoms than men. COVID-19 symptoms were also more common and more severe in older people, but the correlation was not very strong. Immune fitness was, as expected, strongly correlated with both count and severity. BMI was not found to correlate with the number or severity of symptoms. Stepwise regression analysis was used to create a model to explain variance, including sex, age, BMI, underlying disease, and immune fitness as predictor variables. Explaining 26% of the variance, this model found that the three variables that most predicted number of symptoms were immune form (2019), immune form (DL), and having an underlying disease. In a second analysis, these variables were also found to be the best predictors of severity.

A second analysis was performed on the COTEST study, conducted during the Delta outbreak at healthcare testing locations, with a total of 925 participants. As was done later in the pandemic, participants were able to be tested for COVID-19, revealing 88 positive cases. As expected, those who tested positive for COVID-19 reported a significantly higher average number of symptoms than those who tested negative, although 8% were asymptomatic. This study looked at immune form (2019) and immune form at the time of testing (immune form T). Significant correlations between immune form (2019 and T) and number/severity of symptoms. Correlations between immune fitness (2019) in the two groups were of similar magnitude, but correlations with immune fitness (T) were significantly more robust in negative individuals. Stepwise regression analysis was performed again, using the same predictor variables (immune form (T) replacing immune form (DL). This created a model explaining 30.9% of the variance in the number of symptoms and a second model explaining 29.9% of symptom severity. In this study, the three most important factors in both models were immune fitness (T), immune fitness (2019), and gender. who tested positive for SARS-COV-2, the only significant predictor variable was immune fitness (2019).


According to these studies, immune fitness is the most important factor in reducing the severity and number of symptoms of COVID-19. Taking the cohort as a whole, immune fitness (2019) was the strongest predictor, although immune fitness (T) was more important among COTEST participants who tested positive.

In conclusion, the authors argue that governments have a responsibility to not rely solely on pharmaceutical interventions to prepare for future pandemics that epidemiologists predict will become more frequent, but should also strive to increase immune fitness. of the general population through campaigns that promote a healthy lifestyle.

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