People with addictions at risk for breakthrough COVID

Researchers believe related health issues might heighten the risk

Vaccinated people with substance use disorders may be at a higher risk for experiencing a breakthrough COVID-19 case, a new study shows.

Research conducted earlier in the pandemic showed that people with addictions were already more likely to contract, and experience serious complications from, COVID-19. Now, with the vaccines widespread, that same population is still at risk, according to the study by researchers at Case Western University in Cleveland, Ohio, and the U.S. National Institute on Drug Abuse.

The last year and a half has been particularly difficult for people in addiction, between the heightened risk for COVID and a rapidly escalating overdose crisis — exacerbated by the pandemic — that killed more than 93,000 people in 2020 alone.

Although the vaccine is still highly effective and the risk of a breakthrough infection relatively low, researchers believe that the high prevalence of other co-occurring health issues among people with addiction may be behind the increased risk for a breakthrough infection. When the study authors controlled for adverse socioeconomic health determinants — like issues with employment and housing — and comorbidities, the risk of breakthrough infections for people with and without a substance use disorder was the same.

The only exception was in patients diagnosed with a cannabis use disorder, a generally younger group of patients who were still found to be more likely to develop a breakthrough infection, even after researchers controlled for other factors.

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

The study looked at more than 579,000 people fully vaccinated against COVID between December 2020 and August 2021. Of that group, 30,183 patients had been diagnosed with a substance use disorder. The study found that seven per cent of those with a SUD had a breakthrough infection at least 14 days after their second shot, compared to 3.6 per cent of people without a substance use disorder. People with a substance use disorder were also more likely to experience a serious breakthrough infection, researchers found.

Rong Xu, a professor of biomedical informatics at Case Western and one of the study’s authors, said the findings show that an already vulnerable group is still at risk from the virus. “The population with substance use disorder, they do have a lot of comorbidities, which makes them vulnerable to other diseases,” Xu said. It’s important, she said, to treat substance use from a physicalhealth perspective, as well as a behavioural one.

“We don’t focus as much on the long-term health consequences of substance use on much of our body systems, including the immune system,” she said.

In a press release last week, National Institute on Drug Abuse director Nora Volkow, another of the study’s authors, stressed that people with addiction should get vaccinated and that the overall risk of COVID among vaccinated members of the group is still very low.

“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.”