6. Covid 19
There are several strains of Covid 19.
Covid 19 infects multiple organs.
Many unknowns.
Normal timeframe to develop a vaccine is 10 to 15 years. There are side effects of medication and a vaccine is no different. If rush through especially with shortcuts taken, there could be unforseen side effects, perhaps fatal.
Flu viruses are always mutating. Scientists have already discovered more than 30 mutations of Covid 19.
There is no "universal" vaccine for all the flu viruses.
Be prepared for the long haul - A Pandemic World.
(A "Walking Dead" world isn't so far fetched, is it?)
https://www.freemalaysiatoday.com/category/nation/2020/06/03/british-expert-says-social-distancing-is-best-as-covid-19-vaccine-uncertain/
https://www.freemalaysiatoday.com/category/highlight/2020/05/20/chinas-new-outbreak-shows-signs-virus-could-be-mutating/
https://www.rt.com/uk/487014-shock-syndrome-development-as-children/
https://www.malaymail.com/news/world/2020/04/22/alarmed-as-covid-patients-blood-thickened-new-york-doctors-try-new-treatmen/1859309
https://www.cbc.ca/news/canada/toronto/strange-symptoms-flare-ups-weeks-long-illnesses-for-some-covid-19-survivors-1.5587446