Earlier this month, the US Centres for Disease Control and Prevention updated its Covid-19 recommendations to specifically target older adults and people with serious underlying medical conditions, labelling this group as "higher risk."
Another group who could be particularly vulnerable to the coronavirus and has not received as much attention are people who smoke, vape or have substance-use disorders, the CNN reported.
"[T]he research community should be alert to the possibility that [Covid-19] could hit some populations with substance use disorders particularly hard," National Institute on Drug Abuse director Dr Nora Volkow wrote in a blog post published last week.
"Because Covid-19 attacks the lungs, those who smoke tobacco or marijuana or who vape may be especially threatened," Dr Volkow said.
"When someone's lungs are exposed to flu or other infections the adverse effects of smoking or vaping are much more serious than among people who do not smoke or vape," Stanton Glantz, professor of medicine and director of the Centre for Tobacco Research Control and Education at University of California, San Francisco, wrote in a blog post.
"Vaping affects your lungs at every level. It affects the immune function in your nasal cavity by affecting cilia which push foreign things out...[T]he ability of your upper airways to clear viruses is compromised," Glantz said.
The CDC recently reported that young adults under age 44 make up a big part of Covid-19 hospitalisations in the US, and Glantz questions whether the vaping epidemic might have contributed to this.
"Some of my pulmonary [colleagues] have noted people under 30 [with Covid-19] ending up in hospitals and a couple were vapors," Glantz said, adding that there hasn't been enough research or evidence to support whether there's a link.
According to Glantz, the odds of a coronavirus case becoming more severe - and at the most extreme, lead to death - were 14 times higher among people who had a history of smoking compared to those who did not smoke.
A study from China published in the peer-reviewed Chinese Medical Journal in February found those with a history of smoking had a 14 percent higher risk of developing pneumonia.