NIH: People with substance use disorders may be at higher risk for breakthrough COVID-19

WASHINGTON - The risk of breakthrough COVID-19 infections may be higher among vaccinated patients with substance use disorders, a new study by the National Institutes of Health found.

Researchers who conducted the study, published Wednesday in "World Psychiatry," analyzed electronic health records of nearly 580,000 fully vaccinated people — with and without substance use disorders — in the United States. 

Data taken between Dec. 1, 2020 and Aug. 14, 2021 found the risk of COVID-19 breakthrough infections among vaccinated patients with substance use disorders was low overall but higher than the risk among vaccinated people without substance use disorders. 

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For example, 7% of vaccinated people with substance use disorders had a breakthrough infection during the study, compared with 3.6% of vaccinated people without substance use disorders. The risk of breakthrough infection varied slightly among people with different substance use disorders, ranging from 6.8% for people with a tobacco use disorder to 7.8% for those with a cannabis use disorder.

The study found that co-occurring health conditions and adverse socioeconomic determinants of health, which are more common in people with substance use disorders, appeared to be largely responsible for the increased risk.

People with substance use disorders — such as alcohol, cannabis, cocaine, opioid, and tobacco use disorders — also had elevated rates of severe outcomes, including 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 NIDA Director Dr. Nora D. Volkow, one of the lead authors on the study. "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."

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A previous study conducted in the early stages of the coronavirus pandemic found that people with substance use disorders were at an increased risk of COVID-19 infection, and were more likely to have severe disease or death.

That study, published in "Nature," found the risk was particularly higher for seniors with substance abuse disorders in comparison to adults and African American people with substance abuse disorders when compared to Caucasians. 

"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 Dr. 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."

A breakthrough case is when a fully vaccinated person gets infected with the coronavirus. While breakthrough cases have become more common as the highly contagious delta variant spreads, the COVID-19 vaccines have still proven remarkably protective and effective against hospitalizations and deaths.

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COVID-19 vaccines work by teaching the body to recognize the novel coronavirus. If a person is exposed to it after vaccination, their immune system should be ready to spring into action and fight it. If a person does end up getting sick despite vaccination, experts say the shots are very good at reducing the severity of the illness.

In studies, the two-dose COVID-19 vaccines by Pfizer and Moderna were around 95% effective at preventing illness, while the one-shot Johnson & Johnson shot was 72% effective, though direct comparisons are difficult. So while the vaccines are very good at protecting us from the virus, it’s still possible to get infected with mild or no symptoms, or even to get sick.

Even still, If you do end up getting sick despite vaccination, experts say the shots are very good at reducing the severity of the illness.

Most people with breakthrough infections experience mild illness, said Dr. William Moss, a vaccine expert at the Johns Hopkins Bloomberg School of Public Health.