Though vaping has been around for years, it exploded into the mainstream of American culture and politics in 2019. When 2019 began, an adult in Massachusetts could buy any number of vaping products, including vape "juices" in any number of flavors. Then, for about three months, that same adult couldn't even buy a tobacco-flavored nicotine vape. But as the year ends, adults are again able to buy vaping products -- just not in any kind of flavor.

For the first few months of 2019, the conversation around vaping focused on keeping teens from using the products and Baker's proposal to expand the cigarette excise tax to e-cigarettes and vaping products. The Baker administration first flagged vaping as a "public health crisis" in April when it rolled out a public information campaign to raise awareness among middle and high school students about the dangers of vaping.

Over the summer, cases of serious -- even fatal -- and unexplained lung injuries and illnesses caused by vaping began to spread around the country and vaping entered the mainstream consciousness.

"We have a problem in our country. It's a new problem. It's a problem nobody really thought about too much a few years ago, and it's called 'vaping' -- especially vaping as it pertains to innocent children. And they're coming home and they're saying, 'Mom, I want to vape.' And the parents don't know too much about it. And nobody knows too much about it, but they do know it's causing a lot of problems," President Donald Trump summed it up in the Oval Office on Sept. 11. "And we're going to have to do something about it."

About that same time, Baker convened a group of medical professionals to learn more about the health effects of vaping and to weigh his administration's options for addressing the emerging problem. On Sept. 24, the governor declared an official public health emergency and banned the sales of all vape products -- flavored, unflavored, nicotine or cannabis -- for four months.

"We as a commonwealth need to pause sales in order for our medical experts to collect more information about what is driving these life-threatening vaping-related illnesses," Baker said.

Opponents challenged the governor's edict and the courts whittled the four-month ban down to three months and ruled that only the Cannabis Control Commission could ban marijuana vapes (it then quarantined all vaping products in tandem with Baker's ban). Vape shops were forced out of business, consumers learned the quickest routes to New Hampshire and a new politically-active group made itself known -- the vaping voter.

In all, Massachusetts public health officials reported 93 cases (31 confirmed and 62 probable cases) to the U.S. Centers for Disease Control and Prevention, including the deaths of three people in Massachusetts from vaping-associated lung injury.

With the Christmas Eve expiration of Baker's ban on the horizon, the Legislature in late November passed a bill banning all flavored tobacco products, including vaping liquids and menthol cigarettes. When he signed it, Baker announced that the ban would instead end Dec. 11, when the Public Health Council planned to adopt new state regulations for e-cigarettes and vaping.

With the new rules in place -- including restrictions on the amount of nicotine allowed in vaping pods sold at convenience stores and a requirement that retailers warn of the dangers of vaping -- state officials acknowledged that they still don't know why people are getting sick from vaping.

"We don't understand what is causing these illnesses," Public Health Commissioner Monica Bharel told reporters after the new regulations were approved. "From a public health point of view, we cannot recommend that anybody use vaping or e-cigarette products at this time."

Nonetheless, vaping products were back on the shelves after nearly three months of prohibition. Maybe the discovery of the cause of 2019's vaping injuries will be one of the top stories of 2020.