In many U.S. states, reported rates of COVID-19 are rapidly increasing, and a high proportion of those contracting the disease are young adults. 

In Florida, for instance, the average age of those infected with COVID-19 is now 21. Similar trends can be found in other states, including Arizona, California and Texas.

Partially due to the perception that they are less vulnerable to the severe symptoms of COVID-19, too many young people have failed to adhere to the safety measures put in place by the CDC. On college campuses, including at the University of California-Berkeley and at the University of Washington, summer fraternity parties have led to notable increases in students testing positive for the novel disease. 

Since the beginning of the pandemic, young adults were asked to wear masks and social distance, most importantly, to reduce their chances of passing the virus on to more vulnerable family members. 

But a new study led by researchers at the University of California San Francisco (UCSF) suggests that, perhaps, young people should also worry about themselves, as age alone may not be enough to shield severe symptoms. 

The researchers examined data from a nationally representative group of 8,400 men and women ages 18-25 and concluded that 33 percent of young men and 30 percent of young women included in the study were “medically vulnerable.” 

A UCSF news release on the study references data from the CDC to suggest that while those over the age of 65 are still significantly more likely to be hospitalized than younger people, the gap is shrinking. 

In mid-April, there were less than nine hospitalizations per 100,000 of individuals ages 18-29, compared to more than 128 per 100,000 of the population for patients over 65. By the end of June, the figures for both increased to 34.7 and 306.7, respectively. The share of hospitalizations for young adults increased by 299 percent, compared to a 139 percent increase in hospitalizations for those over 65. 

Determining who is “vulnerable”

The CDC lists a number of health conditions and habits — referred to as “indicators” — that have been proven to increase individuals’ likelihood of experiencing severe symptoms, which can lead to hospitalization and even death. 

These risk factors include heart conditions, diabetes, current asthma, immune conditions (such as lupus, gout and rheumatoid arthritis), liver conditions, obesity and smoking a cigarette or cigar. The researchers also added e-cigarette smoking to the list because it has “been identified as contributory to respiratory and immune illness.”

Since there was no significant, reliable data on the relative impact of each CDC indicator, the researchers decided that having at least one of the indicators made someone vulnerable. So, among smokers, for example, 100 percent were deemed vulnerable for severe COVID-19. 

Smoking is the leading risk factor 

Notably, smoking was determined as the leading cause for medical vulnerability among young adults. Out of the non-smokers in the study, only about 16 percent were deemed vulnerable. 

“Recent evidence indicates that smoking is associated with a higher likelihood of COVID-19 progression, including increased illness severity, ICU admission or death,” first author Sally Adams, of UCSF’s National Adolescent and Young Adult Health Information Center, said in the release. “Smoking may have significant effects in young adults, who typically have low rates for most chronic diseases.”

And, notably, young adults are starting to smoke at higher rates than adolescents, she added, which is a reversal of previous trends. 

Using data from the National Health Interview Survey, the researchers found that over the preceding 30 days, 10.9 percent of young adults had smoked a cigarette, 7.2 had smoked an e-cigarette and 4.5 had smoked a cigar product. 

“The risk of being medically vulnerable to severe disease is halved when smokers are removed from the sample,” senior author Charles Irwin Jr., who is a professor of pediatrics and director of the Division of Adolescent & Young Adult Medicine at the UCSF School of Medicine and the UCSF Benioff Children’s Hospital, said in the release. “Efforts to reduce smoking and e-cigarette use among young adults would likely lower their vulnerability to severe disease.”

Overall, 20 percent of the young people included in the study smoked, 8.6 percent had asthma, 3 percent suffered from obesity, 2.4 percent had immune disorders, 1.2 percent had diabetes, 0.6 percent had a liver condition and 0.5 percent had a heart condition. 

Some of the indicators had gender differences. Significantly fewer young women smoked, so their overall medical vulnerability is lower than that of young men (29.7 percent compared to 33.3 percent). However, young women were more likely than men to have asthma (10 percent compared to 7.3 percent), to be obese (3.3 percent compared to 2.6 percent) and to have immune conditions (3.2 compared to 1.6 percent).