COVID-19 and seasonal influenza: dual burden and epidemic intelligence from Flu vaccine
COVID-19 and seasonal influenza: dual burden and epidemic intelligence from flu vaccine
Sewell et al. briefly highlights the role of humoral and T-cell-mediated immunity to fight against COVID-19. As we wait for a successful vaccine against COVID-19 following recent successful phase-1 and phase-2 vaccine trials,[2,3] there is a crucial challenge of subsequent waves of COVID-19 including a winter wave. For the first time in recent history, we are on the verge of a dual burden of COVID-19 pandemic and a seasonal influenza epidemic. Each of these can result in life-threatening illnesses and death, especially in vulnerable populations (e.g., elderly, people with underlying conditions, ethnic minority). With available evidence of a beneficial effect of physical distancing, it was suggested that England may need another lockdown in winter. In the absence of a successful vaccine against COVID-19, what role can the flu vaccine play to mitigate the dual burden of COVID-19 and seasonal influenza?
Healthcare burden, and case identification:
COVID-19 and seasonal influenza share similar signs and symptoms. Therefore, in settings with a low Flu vaccination coverage, more patients would seek medical help with very similar symptoms, making it more challenging for the healthcare providers to distinguish between seasonal influenza and COVID-19. This would, consequently, (a) require more testing kits, which are already scarce in many countries around the world, (b) increase the burden on healthcare providers, and (c) increase the exposure of seasonal influenza patients to SARS-CoV-2.
A higher coverage of Flu vaccination would help reduce the rate of hospitalizations due to severe influenza, especially in elderly population. This would reduce the burden on healthcare system and help allocate more resources available to tackle COVID-19 epidemic. It would also reduce the exposure of elderly patients with seasonal influenza to SARS-CoV-2.
Flu vaccine and epidemic intelligence:
A higher flu vaccine coverage may also provide some epidemic intelligence regarding (i) potential cross-immunity of Flu vaccine against COVID-19, and (ii) emergence of potential new viral strain(s). The potential cross-immunity, which is still unknown, can be hypothesised if we see a substantial difference in the number of COVID-19 cases between settings with high- and low-coverage of flu vaccine. However, if we see an unusually high proportion of people with influenza-like symptoms even in settings with high Flu vaccine coverage, and if we find that these patients are not affected by SARS-CoV-2, we may suspect the emergence of potentially (mutated) new strain(s) of seasonal influenza, or COVID-19, or a new virus species. Such epidemic intelligence will be invaluable for early detection of, and preparation for, a potential epidemic/pandemic. Therefore, expanding the Flu vaccine coverage ahead of seasonal influenza season would be invaluable in tackling the dual burden of COVID-19 pandemic and seasonal influenza epidemic.
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Competing interests: No competing interests