Patients in treatment for heroin addiction appear to be far more resilient to Covid-19 than initially believed, with researchers suggesting drugs such as methadone may protect against the disease.
At the start of the pandemic last year it had been assumed Covid would disproportionately impact drug addicts due primarily to their associated health problems.
However, according to new Irish research Covid rates have been much lower than expected among people receiving opiate agonist treatment (OAT), a therapy which uses methadone or similar drugs to treat opioid addiction.
Of the 565 attendees at the HSE's National Drug Treatment Centre (NDTC) in inner-city Dublin, none displayed serious illnesses indicative of Covid and none died as a result of the disease throughout the first three waves of the pandemic.
Antibody tests were carried out on a subset of patients, comprising 103 people. Researchers found only two patients (1.9 per cent) had contracted Covid-19 despite several more patients reporting close contacts with a Covid sufferer. An “equivocal” Covid result was found in a third patient.
The prevalence of Covid in the general population in Dublin was almost double at 3.1 per cent, according to a separate study conducted in the previous month.
“The expectation that Covid-19 would spread rapidly through the OAT population did not materialise here or elsewhere,” the authors concluded.
The results of the study, which was carried out by researchers at the NDTC and published in the Irish Journal of Medical Science, tally with larger international studies.
"Despite an estimated 654,000 opioid users in Europe receiving OAT, most health professionals surveyed did not report cases," the researchers said, while those that did reported them in very low numbers.
Another Dublin-based study of homeless drug-users also showed an “unexpectedly low incidence of Covid-19 and no deaths”, the authors said.
The NDTC study was carried out between July and October 2020, during which Ireland experienced two waves of the disease.
Researchers postulated that medications such methadone and buprenorphine, which are used as therapeutic substitutes for heroin, may have a “protective effect” against Covid.
The two patients who did test positive for Covid were on low dose of methadone at the time, and their symptoms quickly resolved.
The study said it is also possible the cohort had a low level of exposure to the disease. However, researchers added that NDTC patients were at a broadly similar risk compared to other Dubliners and “at a theoretically higher risk due to routine sharing of drug paraphernalia, cigarettes, and masks and personal challenges in maintaining social distancing”.
Public health measures such as providing hotel accommodation for homeless people could be responsible but they do “not fully explain” the low levels of Covid amongst people in treatment for heroin addiction.
Instead of Covid-19, the authors said the main risks to this group during the pandemic was “increased risk of drug overdose due to changes in service delivery and drug market changes”.
The study called for more research into the possible protective effects of opioid-substitution therapy.