COVID-19 is an unpredictable virus: some people catch it and are asymptomatic. Others, on the other hand, can end up in hospital. The Covid vaccines deployed against the viral disease have made it far less unpredictable by making it less severe. Despite the palpable benefits of getting vaccinated, breakthrough Covid infections have cropped in fully vaccinated populations.
This is to be expected – the vaccines do not stop you getting COVID-19. But they do render its impact far less serious in most people.
However, a new risk factor has been linked to breakthrough infections of Covid that put those affected at an eight percent higher risk of Covid post-vaccination.
The key finding of the study, published in World Psychology, is that those with a substance use disorder (SUD) – a dependence on marijuana, alcohol, cocaine, opioids and tobacco – were almost eight percent more likely to get the Covid while in those without SUD the number drops to 3.6 percent.
Individuals with SUDs are at increased risk for COVID-19 infection and for adverse outcomes of the infection.
“Though vaccines are highly effective against COVID-19, their effectiveness in individuals with SUDs might be curtailed by compromised immune status and a greater likelihood of exposures, added to the waning vaccine immunity and the new SARS-CoV-2 variants,” the researchers in the study theorised.
To investigate the association, the researchers conducted a population-based cohort study.
They assessed the risk, time trends, outcomes and disparities of COVID-19 breakthrough infection in fully vaccinated SUD patients starting 14 days after completion of vaccination.
The study included 579,372 individuals (30,183 with a diagnosis of SUD and 549,189 without such a diagnosis) who were fully vaccinated between December 2020 and August 2021, and had not contracted COVID-19 infection prior to vaccination.
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The researchers analysed de-identified electronic health records from 63 health care organisations in the US.
Among SUD patients, the risk for breakthrough infection ranged from 6.8 percent for tobacco use disorder to 7.8 percent for cannabis use disorder, all significantly higher than the 3.6 percent in non-SUD population.
Breakthrough infection risk remained significantly higher after controlling for demographics (age, gender, ethnicity) and vaccine types for all SUD subtypes, except for tobacco use disorder, and was highest for cocaine and cannabis use disorders.
When the researchers matched SUD and non-SUD individuals for lifetime comorbidities (underlying health conditions) and adverse socioeconomic determinants of health, the risk for breakthrough infection no longer differed between these populations, except for patients with cannabis use disorder, who remained at increased risk.
What’s more, the risk for breakthrough infection was higher in SUD patients who received the Pfizer than the Moderna vaccine.
In the vaccinated SUD population, the risk for hospitalisation was 22.5 percent for the breakthrough cohort and 1.6 percent for the non-breakthrough cohort, while the risk for death was 1.7 percent and 0.5 percent respectively.
No significant age, gender and ethnic disparities for breakthrough infection were observed in vaccinated SUD patients.
“These data suggest that fully vaccinated SUD individuals are at higher risk for breakthrough COVID-19 infection, and this is largely due to their higher prevalence of comorbidities and adverse socioeconomic determinants of health compared with non-SUD individuals,” the researchers concluded.
They added: “The high frequency of comorbidities in SUD patients is also likely to contribute to their high rates of hospitalisation and death following breakthrough infection.”
Meanwhile, unvaccinated pregnant women make up one fifth of most critically ill coronavirus patients in England, it has been revealed today.
The National Childbirth Trust dubbed the statistics a “damning indictment of the lack of attention given to this vulnerable group as restrictions have eased”.
The figures show that between July 1 and September 30, 17 percent of patients receiving treatment through a lung-bypass machine were unvaccinated pregnant women.