If there is one thing we have learned from the COVID-19 pandemic, it is that we were not nearly as prepared for a pandemic as we should have been. However, young children, who we often perceive as most vulnerable to disease, seem to have fared best, possibly revealing a new strategy we can take advantage of as we prepare for future public health challenges.
Throughout the pandemic, researchers and public health officials have come to understand that children are at significantly lower risk of developing severe symptoms from COVID-19 than adults. Even though not many children have been able to get vaccinated, reports suggest that fewer than 1% of children infected with the virus required hospitalization, and death rates fall around 0.01% . While the mechanism of this immunity is not fully understood, some scientists propose that developmental changes in the immune system may give children an advantage at fighting off infections from unknown viruses. Whereas adults keep track of previous viruses they have encountered and respond swiftly when they reappear, children lack opportunities to build up this adaptive immune system. Rather, children possess a strengthened innate immune system that offers them nonspecific protection against infection .
Children’s enhanced immunity indicates that when facing new viruses, the adaptive immune system may be less effective than the innate immune system, which does not rely on the recognition of past antigens . Effectively identifying unknown pathogens and coordinating a more general response without specific antibodies, the immune system that children possess seems to be better suited at preventing new viruses—including the coronavirus—from multiplying and spreading throughout the human body .
Uncovering a possible weak spot in our approach to vaccinations, this discovery shows us how specific and memory-dependent immune responses can be flawed . Generally, vaccines work by introducing us to weakened or inactive versions of harmful pathogens so that our immune systems can learn to identify the specific pathogen and target it with antibodies. This strategy utilizes our adaptive immune response—recognizing a specific virus and storing it in our immune memory. Yet, COVID-19 has shown us that we must find a way to use vaccines to develop broad immunity, protecting against a diverse group of viruses, including ones we have not experienced yet.
Thankfully, scientists have already begun this process in their hunt for a universal flu vaccine. Every flu season, new flu vaccines are released as researchers predict which strain of the virus will be most prevalent; however, flu vaccines remain somewhat ineffective as the vaccine only slightly reduces one’s risk of contracting influenza . Scientists attribute this difficulty in developing an effective vaccine to the ability of the flu virus to mutate easily and change the structure of its spike proteins to avoid detection by the immune system.
Currently, researchers are looking into new vaccines that could prepare the body to recognize a wide range of flu viruses. The NIH has begun clinical trials with a new vaccine candidate that uses the stem region of an outer protein on the virus rather than the head region, which changes structure frequently between different strains . If the immune system could target the stem region of the virus, which is more stable between different strains, then the new vaccine could be used to protect against a wide range of flu-like viruses . This new vaccine candidate has not passed through clinical trials yet, but if it could, it may help protect us against future pandemics. Rather than targeting specific antigens to which we have experienced, a universal vaccine could develop broad immunity, even against new viruses we have yet to come across.
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