The findings, published in World Psychiatry and conducted by researchers of the National Institute on Drug Abuse (NIDA), revealed that the risk of breakthrough infection among vaccinated individuals with substance use disorders was higher than the risk among vaccinated people without substance use disorders.
The study also discovered that co-occurring health issues and negative socioeconomic health factors, which are more prevalent in people with substance use disorders, appear to be substantially responsible for the higher risk of SARS-CoV-2 breakthrough infections. People with drug use disorders, such as alcohol, cannabis, cocaine, opioid, and tobacco also had higher risks of severe outcomes, such as hospitalization and death, following breakthrough infections.
“First and foremost, vaccination is highly effective for people with substance use disorders, and the overall risk of COVID-19 among vaccinated people with substance use disorders is very low.” said Nora D. Volkow, one of the lead authors on the study and Director of NIDA.
“We must continue to encourage and facilitate COVID-19 vaccination among people with substance use disorders, while also acknowledging that even after vaccination, this group is at an increased risk and should continue to take protective measures against COVID-19.”
Analyses undertaken in the early phases of the pandemic discovered that people with substance use disorders were more likely to become infected with SARS-CoV-2 and to develop severe disease requiring hospitalisation or resulting in death. This was especially true for Black folks suffering from a substance abuse disorder.
However, people with substance use disorders were not expressly included in these scientific trials examining the efficacy of vaccines currently available. As many people with substance use disorders are immunocompromised as a result of drug use and co-occurring conditions, researchers expected that this population would be at a higher risk of developing new infections after being vaccinated.
To know more, researchers examined electronic health records of nearly 580,000 people in the United States with and without substance use disorders who were fully vaccinated against COVID-19 between December 1, 2020, and August 14, 2021, and who had not previously been infected with SARS-CoV-2. The infection status was determined by the ICD-10 diagnosis code COVID-19 or the presence of SARS-CoV-2 and associated RNA in a lab test.
They calculated the proportion of individuals in each group who were infected with SARS-CoV-2 at least 14 days after receiving their final dose. After matching patients with and without substance use disorders for demographic characteristics, socioeconomic factors that influence health, such as housing or employment instability, and lifetime physical illnesses, such as high blood pressure, heart disease, obesity, or diabetes, this analysis was repeated. The researchers also looked to see if fully vaccinated patients with breakthrough infections had a higher risk of hospitalization leading to death than matched people who did not have breakthrough infections.
The researchers discovered that individuals with substance use disorders had a significantly higher risk of developing a breakthrough infection than those who did not: 7 percent of vaccinated people with substance use disorders had a breakthrough infection during the study, compared to 3.6 percent of vaccinated people who did not have substance use disorders. The probability of developing a new infection differed somewhat amongst those with different drug use disorders, ranging from 6.8 percent for those with tobacco use disorder to 7.8 percent for those with cannabis use disorder.
According to the study, the increased risk of breakthrough infections in patients with substance use disorders is mostly linked to co-occurring conditions and poor socioeconomic status. When these factors were taken into account, patients with most substance use disorders no longer had an increased risk of developing a new illness.
The only exception was persons with cannabis use disorder, who were still 55 percent more likely to suffer breakthrough infections than people without drug use disorders, despite being younger and having less co-occurring health issues than those with other substance use disorders. The scientists suggested that factors such as cannabis’s negative effects on lung and immunological function may have contributed to this group’s increased risk of breakthrough infection.
Furthermore, irrespective of the existence of substance use disorders, breakthrough infections were found to significantly increase the likelihood of severe outcomes, including hospitalization and death. People with drug use problems required hospitalization 22.5 percent of the time for a breakthrough infection, and 1.7 percent died throughout the study period, compared to 1.6 percent and 0.5 percent for people with substance use disorders but no breakthrough infection. Furthermore, patients with substance use disorders had a higher chance of severe outcomes after a breakthrough infection than those without substance use disorders.
“From previous studies, we knew that people with substance use disorders may be particularly vulnerable to COVID-19 and severe related outcomes. These results emphasize that, while the vaccine is essential and effective, some of these same risk factors still apply to breakthrough infections,” said Rong Xu, Ph.D., professor in the Center for Artificial Intelligence in Drug Discovery at Case Western Reserve University.
“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.”
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