Monkeypox was first identified in 1958, and appears to be endemic among some mammals in parts of central Africa. There have been small outbreaks or clusters of cases outside of Africa fairly frequently since 2001, and outbreaks and case clusters have been happening somewhere in the world almost every year since 2017 (the exception being 2020, when worldwide travel was Covid-diminished).
So, this outbreak is not sudden, it's just a disease endemic in Africa that infrequently has significant outbreaks in the west, and thus gets little western MSM attention. In the current outbreak many cases have been traced back to one or two widely attended "Pride" festivals. Whether the "close contact" was bar room or concert close or closer is knowledge I can forgo. At this point, the outbreak looks to be isolated pockets and not spreading.
Vaccine ... the history of this is less than fascinating, but trying to be brief:
* After smallpox having been, in the 1970s, declared eradicated and routine vaccination largely ceased, the presence of lab samples of the virus in countries that had become unstable in the 1990s and beyond sparked concern that the virus could be used as a weapon;
* Technology having marched on, a new smallpox vaccine was developed;
* This vaccine was approved in EuroLand in 2013, and in 2019 in the US; until recently, the US had a stockpile of some 24 million doses;
* This vaccine is also effective against monkeypox.
