Antibiotics are drugs designed to treat infections caused by bacteria (for example, skin infections). They don't work on infections caused by other microbes such as viruses (including COVID and flu) or fungi (for example, thrush).
Beyond treating bacterial infections, antibiotics also have other important uses, like preventing infection during major surgery.
Bacteria have existed for billions of years and are adept at survival. Since the early 20th century when antibiotics were introduced as medicines to fight infections, bacteria have worked out several ways to protect themselves and avoid being killed.
When antibiotics are misused or overused, more opportunities arise for bacteria to develop and improve these protective tools. This contributes to a problem called antibiotic or antimicrobial resistance, where bacteria evolve over time so that antibiotics no longer work against them. This makes infections more difficult to treat as doctors have fewer antibiotics to choose from, in turn increasing the risk of serious illness and death.
But how has the COVID pandemic affected antibiotic use, and the problem of antibiotic resistance? A recent study which analysed pharmaceutical sales data from 71 countries suggests that as COVID cases went up, so did antibiotics sales.
The researchers examined sales of four antibiotic families commonly prescribed in respiratory infections (cephalosporins, penicillins, macrolides and tetracyclines) from March 2020 to May 2022.
They sourced monthly sales data for these antibiotics per 1,000 people, and from a separate database also gathered data on COVID infections. For comparison, the researchers used global antibiotic sales trends from 2018.
Not surprisingly, they found antibiotics sales fell sharply over April and May 2020. This drop was likely a result of fewer infections spreading while people were under strict lockdown measures, and perhaps some people avoiding healthcare.
However, antibiotic sales gradually increased thereafter. The resurgence of non-COVID respiratory viral infections with the easing of lockdowns may have contributed to increased antibiotics sales from 2021 onward. By May 2022, sales had returned to just below pre-pandemic levels.
Using statistical models, the researchers found an association between increasing COVID rates and higher antibiotic sales.
Read more: COVID is caused by a virus - so why are researchers treating it with antibiotics?
COVID and antibiotics
Research has previously identified seasonal spikes in antibiotic use correlating with the winter virus season. This is concerning because antibiotics are designed to target bacteria, and have no effect on viruses such as those which cause colds or flu.
Many antibiotic prescriptions in these cases are inappropriate. However, distinguishing viral from bacterial infection can be difficult clinically, especially in the initial stages of infection. This may explain why patients are sometimes started on antibiotics while waiting for laboratory test results.
In certain situations, antibiotics are appropriate. For example, viral lung infections can damage airways and compromise the normal protective immune responses. This can allow bacteria to attach to airway cells and invade, causing a secondary bacterial infection.
Early in the COVID pandemic, antibiotic prescribing was probably based on previous experience with flu, where rates of secondary bacterial infection had been reported to be as high as 65%. But as the pandemic progressed, data indicated bacterial co-infection in COVID was less than 10%. Specific antibiotic prescribing guidelines for patients with COVID were published.
Yet despite increasing evidence that bacterial co-infection in COVID is low, research has shown antibiotic prescribing among COVID patients has remained high. This latest study provides further evidence that antibiotics are commonly prescribed to COVID patients.
Some limitations
Similar to other large studies on antibiotic consumption, this study uses antibiotic sales data as a proxy for antibiotic use. This sales data is already captured in databases from a number of countries, and is more readily accessible than data on antibiotic prescriptions in many countries, which may not be captured electronically. But because of the nature of the data, we can't draw any conclusions as to how many of the antibiotics purchased were appropriately prescribed.
Further, data on non-COVID infections, which can impact antibiotic prescribing and rates of resistance, was not included. The pausing of routine childhood vaccination programmes during the pandemic probably increased bacterial infection risk in some countries, necessitating increased antibiotic prescriptions. This may have contributed to the trends seen.
When interpreting these findings, it's also important to note that not all continents were represented equally. Some large countries such as Bangladesh were excluded.
Finally, testing protocols vary between countries, so there may have been some inconsistencies in the COVID case data. And access to antibiotics is inconsistent globally, especially in low- and middle-income countries, which likely impacted some countries' sales rates.
The challenge of antibiotic resistance
Antibiotic resistance is a global threat to public health, impacting humans, animals and the environment.
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Inappropriate antibiotic prescribing in COVID could be contributing to the problem. To address this, we need to see more alignment in guidelines and protocols for clinicians, especially linking diagnosis of viral respiratory infections with antibiotic prescribing guidelines. Support for the development of rapid diagnostics to confirm or rule out co-infection would also give clinicians confidence to avoid antibiotics in some patients.
Read more: Coronavirus pandemic is paving the way for an increase in superbugs
More broadly, tackling the issue of antibiotic resistance requires increased public awareness of the issue, enhanced global surveillance of antibiotic use and resistance, improved infection control policies, and better sanitation.
This rests on a coordinated "One Health" approach - a joint global effort across a range of sectors to provide solutions for human, animal and environmental health. This strategy should address health inequalities and will require bespoke interventions, especially in lower- and middle-income countries.
Fidelma Fitzpatrick, Consultant Microbiologist, Beaumont Hospital, Dublin, Ireland and Professor and Head of Department, Clinical Microbiology, RCSI University of Medicine and Health Sciences
Deirdre Fitzgerald Hughes, Senior Lecturer, Clinical Microbiology, RCSI University of Medicine and Health Sciences
