A novel coronavirus, SARS-CoV-2 was identified in Wuhan, China. The disease caused by the virus can range in severity from asymptomatic to acute respiratory distress syndrome (ARDS) and death. Primary dengue infection results in IgE mediated sensitization against dengue virus proteins. These IgE bind to receptors on mast cells. Upon subsequent exposure to the antigen recognized by the IgE, mast cell degranulation occurs releasing mediators such as histamine. Therefore secondary dengue infection results in urticaria, increased vascular permeability, hypotension, dengue hemorrhagic fever and dengue shock syndrome. A case of "slow rolling anaphylaxis". Vaccines contain proteins derived from coronavirus infected animals as well as other proteins with high homology to SARS-CoV-2. So one could develop IgE mediated sensitization to SARS-CoV-2-like proteins. Therefore, receipt of such vaccines acts like a dengue "primary infection". It results in IgE mediated sensitization. Subsequent SARS-CoV-2 infection becomes a "secondary dengue infection" that has a severe course due to IgE mediated mast cell degranulation and the immune cascade that follows. There are many common observations between COVID-19 and dengue. Elevated levels of ferritin, interleukin-6, vascular endothelial growth factor, D-dimer, coagulopathy, urticaria and ARDS are reported in both diseases. Numerous teams have now confirmed this mechanism that was predicted in Jan 2020, upon analyzing the 2019-nCoV proteome. There are many indicators that mast cell degranulation and histamine release have a major role in COVID-19, dengue and influenza severity. Mast cell stabilizers, antihistamines and anti-parasite treatments may address different aspects of this cascade and thus reduce disease severity.