Age Dependence of COVID-19 – Are Children immune?

Recent debates about how and when it might be safe to reopen schools for the coming academic year has put the spotlight on whether young adults get infected by the novel coronavirus and how many subsequently die of COVID-19?   We had noted early on in the pandemic that the case fatality rate (CFR=deaths/cases) for COVID-19 is highly skewed against older males.  The average 85+ years old male has >30% chance of dying once they are infected which is 1000 times worse than the <0.03% measured for 17- years old young females (see figure below).  While you hear about the occasional death of a teenager this is out of more than hundreds of thousands of teenagers who have been infected in the USA.  Of course, no one knows the long term damage that could be caused by this pernicious and poorly understood virus so young adults are still cautioned against behaving irresponsibly and tempting fate. 

Moreover, it is important to note that there is no evidence that young adults are not as susceptible to getting infected by the novel coronavirus and spreading the disease to older adults.  Early data seemed to show that a lower percentage of young adults got infected primarily because many of them got mild and asymptomatic cases and testing was limited by supply constraints to older and more vulnerable people.  In the early days, California and the rest of the USA behaved like Spain who seemed to show that kids and young adults were 100 times less likely to get infected than older adults.  After the USA expanded its testing capacity it became clear that young adults are just as likely to get infected.  The modestly lower infection rate that is measured for children is probably due to more asymptomatic young adults who don’t even bother to get tested.  However, scientific studies have shown that asymptomatic and pre-symptomatic infectees can still infect others. 

This why the June resurgence that started out with young adults partying on beaches and in bars was initially viewed optimistically by some governors as the young behaving irresponsibly with little impact on the rest of the country laser-focused on reopening the economy as soon as possible.  They downplayed the possibility that young adults will interact with older adults and inevitably spread it to them with disastrous consequences.  The following graph shows that the median age of new cases in Florida cases dropped from 47 years to 33 years in late June but has since then crept up above the median age of all people in Florida at 42.2 years.  Now Florida and many other states are announcing record-high death rates every day. 

This bodes ill for reopening schools too quickly when the infection in many parts of the country is still raging hot.  For those counties that have active virulent outbreaks such as Miami-Dade, the fifth-largest school system in the USA, the prudent thing to do for students, teachers, and parents is to reopen with virtual classrooms.  Children are not immune to COVID-19, nor are their teachers and parents.  Assuming the current outbreak tops out, do we really want to repeat the June resurgence in September?