Covid-19: it's not your grandfather's Influenza. In fact, it's not Influenza.

The Covid 19 Pandemic is frequently compared to the Influenza pandemic of 1918-1920. But is the comparison correct? Corona viruses are not the same as Influenza viruses.

What Does Disappearing Immunity To Covid-19 Mean For A Vaccine?

[...] SARS-CoV-2 is broadly similar to the four coronaviruses that cause about one third of all common colds. Each year, the same four viruses infect us the world over, sweeping the Northern Hemisphere from December to February; south of the Equator from May to July; and in the tropics, year-round. These waves of infection, which with rare exceptions cause minor symptoms only, have repeated year in and year out since the discovery of the virus in the 1960s. The ability of this coronavirus quartet to persist absent alteration is highly unusual. Influenza infections occur annually, too, but the dominant strains differ each time to evade the population’s protective and persistent immune responses.

In the 1970s two independent teams of medical researchers conducted experiments to determine whether or not the same coronavirus strain might reinfect and give a cold to the same person. Volunteers who were deliberately exposed to the virus contracted colds and recovered. A year later, they were again exposed to the same virus—and again were infected and developed cold symptoms. These experiments established that protective immunity to the cold-causing coronavirus is short-lived.

I call this phenomenon "get it and forget it,” and it describes the interaction between these viruses and our immune systems that is so unique. Confronted with a cold-causing coronavirus, our bodies evidently forget that we were infected at all. For us, this leaves us susceptible to annual colds, which are generally harmless but a nuisance besides. For the viruses, this is a winning strategy, as it rids them of the need to change to survive. At present, we don’t understand coronaviruses in sufficient detail to know why our immunity to them so short-lived.* What we do know is that if SARS-CoV-2 behaves as its coronavirus cousins do, Covid-19 is sure to become a seasonally recurring pandemic. [...]

Studies Report Rapid Loss of COVID-19 Antibodies
The results, while preliminary, suggest that survivors of SARS-CoV-2 infection may be susceptible to reinfection within weeks or months.

This is not Influenza. Is this going to keep circulating around, like the common cold corona viruses? God I hope not.