People with Substance Misuse Problems More Likely To Get COVID-19 Even If Vaccinated


Published On: November 8, 2023

New, population-scale research from the United States shows that those with substance misuse disorders have a markedly higher risk of contracting COVID-19 after vaccination than those without.  

In this article, we will look at the paper, published in the World Psychiatry journal in late 2021 

Background to the Research

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Prior to the vaccination programme in the US, there was a lot of evidence that those with underlying illnesses were at greater risk of becoming infected with COVID-19, being hospitalised for the illness and dying from it. This was put down to them having compromised immune systems.

Those with substance misuse disorders were also affected thanks to many such disorders compromising the immune system and those substance users having comorbid medical problems such as lung and heart disease.

The mass vaccination programme in the US without doubt halted the very worst of the pandemic in the country.

Vaccines are not 100% effective, with the three vaccines licensed in the US having the following efficacy at preventing infection:

  • Pfizer-BioNTech 95%
  • Moderna 94%
  • Johnson & Johnson 66.3%

It became clear that in identifying the groups of people most at risk of contracting COVID-19, so measures can be taken to protect them from the greatest harm.

The research paper we look at here is one of a number that looked at a variety of conditions and risk factors for infection after vaccination.

It is also the first large scale study in the world that attempts to assess whether those who misuse substances are at greater risk of infection even after vaccination.

Where the Data Came From

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 Live, non-identifiable medical records were harvested from the TriNetX Analytics network platform.  This gave the medical records for people who had seen medical practitioners from 63 health care organisations.

For this research the authors looked at 579,372 US residents were looked at, 30,183 of whom had a substance misuse disorder.

They had to fit the following criteria to be included:

  • The participants had to have had a medical encounter with one of the healthcare providers since 1st December 2020
  • They had to be fully vaccinated between December 2020 and August 2021, and this had to be on their digital medical record
  • They could not have had a COVID-19 diagnosis before their vaccination or within 14 days of having the vaccination

Though none of the individuals could be identified from their records, the data was live. For instance, as soon as the individual received a positive lab test result for COVID 19 this would show up on the record, and should they have been hospitalised this would show up too.

Social Security data was fed into the system too, so should they have died, the research team would learn of it.

How the Data was Used

Among the 30,183 people with substance misuse disorder, their specific disorder was noted:

  • 21,941 had a tobacco addiction
  • 2,058 had cannabis use disorder 

Other specific use disorders, for instance, methamphetamine use disorder, were not looked at due to the physical numbers being too low for statistical reasons.  

These individuals were divided into four categories: 

  • One group had not been in touch with the source medical organisation after February 2019 to deal with their substance use but had a history of a substance use disorder 
  • The group ‘February 2019’ had had contact with the organisation after February 2019 but before February 2020 with regard their substance use
  • ‘February 2020’ had been in contact after February 2020 but before December 2020 
  • ‘December 2020’ were the group most likely to be dealing with their substance misuse at the time of the study. They had contact with the source medical organisation after December 2020

Both those with and without substance misuse disorders were grouped for factors including race, age, housing situation, employment status, comorbid health conditions and occupational exposure to COVID-19.

This gave the research team the ability to compare groups on a like-for-like basis, to give an accurate estimate of the risks associated with substance misuse disorder and COVID-19 after vaccination.

What the Research Discovered

In this section, we will break down the headline figures to show what the researchers found.

Those with:

  • Alcohol use disorder had a 7.2% chance of breakthrough infection, against the non-substance-using control group’s 3.7%
  • Cannabis use disorder had a 7.8% chance of infection as against the non-substance-using control group’s 2.3%
  • Cocaine was 7.7% as against 2.4%
  • Opioid was 7.1% as against 3.2%
  • Tobacco was 6.8% as against 3.9%

Of note, those in the ‘December 2020’ group (the group most likely to be misused at the time of the research) across all categories of substance use had a far higher overall risk of infection after the vaccination, at 10.8%.

As a whole, this shows a significantly higher risk of breakthrough infection among all those who misuse substances.

How did this show among specific vaccines?

Man lying down with his hand over his head

  • Those vaccinated with the Pfizer vaccine and had a substance misuse disorder had an 8.7% risk as against the control group which had 5.4%
  • Those vaccinated with the Moderna vaccine and who had a substance misuse problem had a 6.3% risk as against the control group’s 4.7%.
  • Numbers weren’t sufficient to assess the risk of those with the Johnson & Johnson vaccine

This shows that those who have the Moderna vaccine who misuse substances have a slightly lower additional risk of infection than those who have had the Pfizer vaccine.

Overall, among those with substance misuse disorders who had caught COVID-19, 22.5% would go on to be hospitalised as against 1.6% of the matched control group.

The paper also showed that there was a 1.7% risk of death among those who had substance misuse problems, as against 0.5% of those without who had been infected.

Implications of the Research

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Those who have a substance misuse problem are at a greater risk of getting COVID-19 even if they have been vaccinated, regardless of their chosen substance. This risk is however substantially lower than if they had not had the vaccine.

Those with a substance misuse disorder who were infected were more than 10 times likelier to be hospitalised for complications associated with the illness than those who had no substance misuse problems. They were also more than three times more likely to have died than those who did not catch COVID-19.  

The research indicates that in the case of cannabis use, this is likely to be something to do with the cannabis users inhaling the drug. It also runs directly against certain rumours promoted in the cannabis-using community that cannabis can somehow combat COVID-19 or prevent infection.

Those who misuse drugs and alcohol need to be aware that they are at heightened risk of catching COVID-19 even after vaccination, and hospitalised if they catch it.

Many who misuse substances are considered risk-takers and may be prone to getting into situations where they are at higher risk of infection.

This might include for instance the alcohol user visiting pubs and bars, or a cannabis user sharing a joint with an infected friend. They should take extra care to avoid being infected, but given the power of such substances over the user, this might not always be possible.

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