Americans who suffer from substance use disorders are at a much greater risk of contracting breakthrough COVID-19 infections after vaccination than those without the disorders, a new study from the National Institutes of Health (NIH) finds.
Researchers studied patient records from about 580,000 vaccinated people, including more than 30,000 with a substance use disorder.
Overall, they found that substance use disorder patients had a seven percent chance of a breakthrough case – double the risk for patients who did not have a substance use disorder.
Patients struggling with cannabis use disorder had the highest risk of a breakthrough case at 7.8 percent.
The findings suggest that individuals struggling with substance use ‘remain vulnerable even after vaccination,’ the researchers say.
This may be because substance use disorder sufferers are likely to face other socioeconomic factors that put them at high risk for Covid – as well as immune systems weakened from drugs and alcohol use, study leader Dr Nora Volkow told.
Patients suffering from substance use disorders have double the risk of a breakthrough case compared to patients who don’t have such a disorder, the NIH study found (file image)
The risk of breakthrough cases for patients suffering from substance use disorder shot up during the Delta surge in summer 2021, but was higher than average before that
Throughout the pandemic, people who suffer from a substance use disorder (or SUD) have faced higher risk for Covid.
SUDs impact a large share of Americans. By one estimate, over 10 percent of adults in the U.S. have experienced a problem with drug use.
People who suffer from SUDs often develop other conditions that put them at a higher risk for Covid, such as diseases of the cardiovascular, immune, and pulmonary systems.
In particular, drugs and alcohol are known to impact patients’ immune systems – reducing their ability to fight off a Covid infection.
Studies from earlier in the pandemic have shown that patients suffering from alcohol use disorder, cannabis use disorder, and other SUDs had a higher risk of both Covid infection and severe symptoms.
A new NIH study suggests that individuals with these disorders remain at higher-than-average risk even after they’re vaccinated.
The study was conducted by researchers at the National Institute on Drug Abuse (NIDA), part of the NIH, and Case Western Reserve University in Ohio.
It was published on Wednesday in the journal World Psychiatry.
The researchers analyzed anonymous electronic health records from about 580,000 fully vaccinated people in the US, utilizing a records system compiling data from 63 health care organizations across the U.S.
This study group of 580,000 included about 30,000 patients who had an SUD diagnosis and 550,000 who did not.
‘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 Volkow, one of the study’s lead authors, in a statement.
Patients with cannabis use disorder (CUD) had the highest risk of a breakthrough case, at 7.8 percent. Breakthrough case risk also increased with age and other conditions
Volkow and her colleagues found that patients with substance use disorders had double the risk of a breakthrough infection compared to patients who did not.
Overall, about seven percent of vaccinated patients with SUDs had a breakthrough infection – compared to 3.6 percent of those not suffering from substance abuse.
Among patients with SUDs, those with cannabis use disorder had the highest risk of a breakthrough case – about 7.8 percent.
But the chance of getting infected was higher among the groups who smoked tobacco (6.8 percent) and cannabis (7.8 percent).
People addicted to cocaine (7.7 percent) and opioids (7.1 percent) also faced an elevated risk, as did alcoholics (7.2 percent).
‘Drugs themselves, from alcohol to opioids to cannabis, directly affect the function of the immune systems,’ Volkow told.
Many drugs also impact lung and heart function, contributing to other health issues, Volkow said.
But substance use disorder patients are vulnerable to Covid due to factors outside their bodies as well.
The researchers noted that the SUD patient group had higher shares of older patients, men, black people, and people with poor socioeconomic conditions than the group of patients without substance use disorders.
All of these groups are known to be more vulnerable to Covid.
In fact, when the researchers adjusted their analysis to account for health and socioeconomic factors, the risk of a breakthrough infection was no longer significantly higher in substance use disorder patients.
Cannabis use disorder was the one exception – these patients remained at a 55 percent higher risk for a breakthrough case when other factors were taken into account.
Cannabis impacts the lungs and the immune system more than other substances – which may explain this increased risk, Volkow said.
‘It is not entirely surprising that those who are dependent on drugs are at an increased risk of developing Covid even once vaccinated,’ Dr Ian Hamilton, an addition expert at the University of York in the UK who was not involved with the study, told
‘We have seen the way that inequality has been amplified during the pandemic.
‘Factors such as poor diet, housing and poverty explain these findings rather than anything specific in the drugs these people use.’
The substance use disorder patients who experienced breakthrough cases were also more likely to have severe cases, the researchers found.
Almost one-fourth percent of SUD patients who experienced a breakthrough case required hospitalization – compared to just 1.6 percent of non-SUD patients who had a breakthrough case.
Similarly, 1.7 percent of SUD patients who experienced a breakthrough case died of their illness, compared to 0.5 percent of non-SUD patients.
While drugs and alcohol can impact the immune system’s ability to fight off a coronavirus infection, this study suggests that socioeconomic factors may be a bigger driver of breakthrough case risk.
‘The reason why people with substance use disorder are more vulnerable overall is that the economic deprivation they have, just like anyone else, leads to less chances to get quality care,’ Volkow told
People with substance use disorders are likely to lack health insurance, which leads to severe chronic conditions, she said.
They’re also more likely to be homeless and to seek out other situations that confer high Covid risk.
Substance use disorder patients are both more likely to be exposed to the virus and more likely to have a severe case, Volkow said.
She noted, however, that future research will be required to back up her team’s findings.