Coronavirus (COVID-19) is currently sweeping the world, and at the time of the writing of this
manuscript (December 20, 2020), 840,000 new cases are being confirmed every day. To date, the
cumulative number of infected people is approaching 100 million and the death toll is in excess of
1.68 million. In Japan as well, the number of newly infected people was almost 3,000 for one day
in December, and the third wave which has now arrived is exceeding the second wave seen in mid-
August. A state of emergency now exists in Tokyo, Osaka and in some other areas.
In this new coronavirus pandemic, aging and the use of immunosuppressants for organ
transplantation and autoimmune diseases are cited as the main factors in the aggravation of
symptoms and death by this disease, which has made it clear that the immune system plays a
pivotal role in protection against this deadly virus. Furthermore, it has become evident that immune
phenomena such as cytokine storms due to overproduction of inflammatory cytokines are deeply
involved in the pathogenesis of COVID-19. Finally, vaccination has begun and will be the key to
overcoming the continued spread of this pandemic of the new coronavirus infection.
In this article, I would like to consider COVID-19 from an immunological point of view.