Substance use disorders such as alcohol and opioid addiction predispose fully vaccinated people to COVID-19 breakthrough infection, hospitalization, and death, although the overall risk is low, according to a US study yesterday in World Psychiatry.
Researchers from Case Western Reserve University and the National Institute on Drug Abuse (NIDA) analyzed the electronic health records of 579,372 coronavirus-naïve patients 12 years and older fully vaccinated from December 2020 to August 2021.
The patients, who received care at one of 64 US healthcare systems, had received two doses of either the Pfizer/BioNTech or Moderna vaccine or one dose of the Johnson & Johnson vaccine at least 14 days before enrollment. Of all patients, 5.2% had a diagnosis of substance use disorder (SUD).
Cannabis abusers at 55% higher risk
Of SUD patients, the risk of breakthrough COVID-19 infection ranged from 6.8% for patients with tobacco use disorder to 7.8% for those with cannabis use disorder, both significantly higher than 3.6% in the non-SUD group.
The risk remained higher after controlling for age, sex, ethnicity, and vaccine types for all SUD subtypes except tobacco use disorder and was highest for those who abused cocaine and cannabis (hazard ratio [HR], 2.06 for cocaine, 1.39 for cannabis). This was despite the relative youth and greater chronic disease burden of the latter group, which the study authors said could be due to the effects of cannabis on lung and immune function.
When the researchers matched patients with and without SUD for chronic conditions and adverse socioeconomic determinants of health (eg, low educational level, unemployment or underemployment), the risk of breakthrough infection was not different, except for those with cannabis use disorder, who were still at 55% higher risk (HR, 1.55).
All subgroups of patients who received the Pfizer vaccine were at higher risk for breakthrough infection than those given Moderna (HR, 1.49 for those with SUD vs 1.45 for non-SUD patients).
Breakthrough infections greatly increased the risk of poor outcomes, regardless of SUD status. The risk of hospitalization among vaccinated SUD patients was 22.5% in the breakthrough group, compared with 1.6% in the non-breakthrough group (risk ratio [RR], 14.4), and the risk of death was 1.7% and 0.5%, respectively (RR, 3.5). Among vaccinated SUD patients, no significant age, sex, or ethnic disparities were identified.
Role of comorbidities, socioeconomic factors
The SUD group was older than their non-SUD counterparts (average age, 59.3 vs 54.7 years), included more men (51.4% vs 43.1%) and Black people (26.2% vs 14.3%), and had more adverse socioeconomic characteristics (7.9% vs 1.2%).
"These data suggest that fully vaccinated SUD individuals are at higher risk for breakthrough COVID-19 infection, and this is largely due to their higher prevalence of comorbidities and adverse socioeconomic determinants of health compared with non-SUD individuals," the researchers wrote. "The high frequency of comorbidities in SUD patients is also likely to contribute to their high rates of hospitalization and death following breakthrough infection."
The authors noted that previous studies have shown that patients with SUD are particularly susceptible to COVID-19 infection and poor outcomes because they tend to be immunocompromised due to their drug use and underlying conditions.
"These results emphasize that, while the vaccine is essential and effective, some of these same risk factors still apply to breakthrough infections," senior author Rong Xu, PhD, of Case Western, said in an NIDA news release. "It is important to continuously evaluate the effectiveness of COVID-19 vaccines and the long-term effects of COVID-19, especially among people with substance use disorders."
The authors concluded that although the overall risk of COVID-19 infection among SUD patients is low, "this group remains a vulnerable one even after vaccination, confirming the importance for vaccinated patients with SUD to continue to take protective preventive measures against the infection."