People with a frequent and diverse use of antibiotics, even in the years before the COVID pandemic, were at significant risk of developing more severe outcomes after infection, including death, a study has shown.

The findings, published in the journal eClinical medicine, acts as a warning against the overuse of antibiotics in people.

Researchers from the University of Manchester found patients with more frequent antibiotic exposure in the past three years were at higher odds of experiencing severe COVID outcomes, including hospital admission and 30-day mortality.

The odds of hospitalised patients dying from COVID-19-related complications in the most frequent antibiotics exposure group were 1.34 higher. And the odds of hospitalisation for patients with the highest history of prior antibiotic use and most antibiotic types were 1.8 times greater.

The team took samples from 0.67 million patients with recent COVID infection, of which 98,420 patients were admitted to hospitals, 22,660 died and 55 unique antibiotics were prescribed.

“One potential explanation may be that frequent antibiotic use increases the likelihood of patients being infected with viruses or bacteria, leading to increased susceptibility to adverse consequences of infection,” said Professor Tjeerd van Staa from The University of Manchester.

van Staa also stated that the medical literature shows that antibiotic treatment might also alter gut microbiota, which can impact metabolic and immune function.

“While in most situations, gut microbiota will recover after stopping an antibiotic course, frequent antibiotic use may affect the resilience of gut microbiomes more seriously,” van Staa said.

Dr Victoria Palin from varsity noted that there is little evidence to suggest that repeated intermittent antibiotic exposure is effective in reducing infection-related complications.

“Indeed, there is mounting evidence, that it can be unsafe. That is why there needs to be more awareness of the impact of long-term antibiotic exposure and its adverse outcomes. We would discourage regular and indiscriminate prescribing of these drugs for self-limiting infections,” Palin said.