New York, Oct 7 : The risk of Covid breakthrough infection was higher among people with substance use disorders than those without, according to a study.
Researchers at the National Institute on Drug Abuse (NIDA), part of the National Institutes of Health, and Case Western Reserve University analysed electronic health records of nearly 580,000 fully vaccinated people in the US.
Their finding was published in the journal World Psychiatry.
People with substance use disorders, such as alcohol, cannabis, cocaine, opioid, and tobacco use disorders, had also elevated rates of severe outcomes, including hospitalisation and death, following breakthrough infections.
The risk of breakthrough infection among vaccinated patients with substance use disorders was low overall.
However, it was still higher than the risk among vaccinated people without the disorders: 7 per cent of vaccinated people with substance use disorders, compared with 3.6 per cent of vaccinated people without.
It could be because substance use disorders make the immune system weak due to drug use and co-occurring diseases.
As a result, researchers hypothesised that this population might be at increased risk of breakthrough infections after getting vaccinated.
Moreover, co-occurring health conditions and adverse socioeconomic determinants of health, which are more common in people with substance use disorders, also could be responsible for the increased risk of SARS-CoV-2 breakthrough infections.
"From previous studies, we knew that people with substance use disorders may be particularly vulnerable to Covid-19 and severe related outcomes.
These results emphasise that, while the vaccine is essential and effective, some of these same risk factors still apply to breakthrough infections," said Rong Xu, 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."
The risk of breakthrough infection varied slightly among people with different substance use disorders, ranging from 6.8 per cent for people with tobacco use disorder to 7.8 per cent for those with cannabis use disorder.
Factors such as adverse effects of cannabis on lung and immune function may have contributed to the higher risk for breakthrough infection in this group, the researchers said.