Study: Drug Use a Factor in COVID Breakthrough Infections

Fully vaccinated individuals with substance use disorders were more likely to have breakthrough COVID-19 infections than those without such disorders, researchers found.

Adjusted analyses found that breakthrough infections were higher in patients with all types of substance use disorder, except tobacco, and were the highest among cocaine users (HR 2.06, 95% CI 1.30-3.25) and cannabis users (HR 1.92, 95% CI 1.39-2.66), reported Lindsey Wang, PhD, of Case Western Reserve University in Cleveland, and colleagues.

However, when matching patients with and without substance use disorders for lifetime comorbidities and social determinants of health, only increased risk for breakthrough infection among cannabis users remained significant (HR 1.55, 95% CI 1.22-1.99), the authors wrote in World Psychiatry.

“This may indicate that additional variables, such as behavioral factors or adverse effects of cannabis on pulmonary and immune function, could contribute to the higher risk for breakthrough infection in this group,” they noted.

Wang’s group added that drugs and alcohol compromise immune function, which could put a person at higher risk of infection. The authors also noted that clinical trials for the COVID-19 vaccines did not “explicitly include” patients with substance use disorders.

They examined electronic health records for 579,372 individuals across 63 U.S. healthcare organizations who were fully vaccinated from December 2020 to August 2021, of which 30,183 had a diagnosis of substance use disorder.

Patients with substance use disorders were older than those without it (mean age 59 vs 55, respectively), and there were more men (51.4% vs 43.1%) and a higher proportion of African Americans (26.2% vs 14.3%).

The percentage of breakthrough infections ranged from 6.8% in patients with tobacco use disorder, to 7.8% in patients with cannabis use disorder, which were significantly higher than the 3.6% in patients without such disorders (P<0.001).

No significant age, gender, and ethnic disparities among breakthrough infections were seen in those with substance use disorders after matching for other demographics, adverse socioeconomic determinants of health, comorbidities, and vaccine types, except for those with cannabis use disorder, among whom African Americans had higher risk than matched Caucasians (HR 1.63, 95% CI 1.06-2.51), the authors noted.

They found that risk of breakthrough infection was higher for the Pfizer vaccine compared with the Moderna vaccine among those with (HR 1.49, 95% CI 1.31-1.69) and without substance use disorders (HR 1.45, 95% CI 1.38-1.53).

Not surprisingly, individuals with substance use disorders and a breakthrough infection had a higher overall risk of hospitalization (risk ratio [RR] 14.4, 95% CI 10.19-20.42) and death (RR 3.5, 95% CI 1.74-7.05) versus those with substance use disorders but without a breakthrough infection.

Limitations to the data included potential misdiagnoses and potential confounders, lack of generalizability to the U.S. population, and lack of vaccination data if vaccines were administered outside of healthcare organizations.

The authors noted there was no variant sequencing information, making it impossible to tell whether waning vaccine efficacy or the Delta variant had contributed to breakthrough infections in this population.