NICE guidelines:

Take Home Messages

Do not offer an antibiotic for preventing or treating Pneumonia if SARS-CoV-2, another virus, or a fungal infection is likely to be the cause.

Evidence as of March 2021 suggests that bacterial co-infection occurs in less than about 8% of people with COVID-19, and could be as low as 0.1% in people in hospital with COVID-19. Viral and fungal co-infections occur at lower rates than bacterial co-infections.

Secondary infection or co-infection (bacterial, viral or fungal) is more likely the longer a person is in hospital and the more they are immunosuppressed (for example, because of certain types of treatment).

The type and number of secondary infections or co-infections will vary depending on the season and any restrictions in place (for example, lockdowns).

Antibiotics do not work on viruses, and inappropriate antibiotic use may reduce availability. Also, inappropriate use may lead to Clostridioides difficile infection and antimicrobial resistance, particularly with broad-spectrum antibiotics.

Identifying secondary bacterial pneumonia

In hospitals or other acute delivery settings, to help identify non-SARS-CoV-2 viral, fungal or bacterial pneumonia, and to inform decision making about using antibiotics, consider the following tests:

• a full blood count
• chest imaging (X-ray, CT or ultrasound)
• respiratory and blood samples (for example, sputum or a tracheal aspirate sample, blood culture)
• urine samples for legionella and pneumococcal antigen testing
• throat samples for respiratory viral (and atypical pathogen) polymerase chain reaction (PCR) testing.

Key Info about CRP test

·       High C-reactive protein levels do not necessarily indicate whether pneumonia is due to bacteria or SARS-COV-2.

·       Low C-reactive protein level indicates that a secondary bacterial infection is less likely.

Recommendations

Do not use C-reactive protein to assess whether a person has a secondary bacterial infection if they have been having immunosuppressant treatment.

Key Info Procalcitonin test

·       There is insufficient evidence to recommend routine procalcitonin testing to guide decisions about antibiotics. Centres already using procalcitonin tests are encouraged to participate in research and data collection.

·       Procalcitonin tests could be useful in identifying whether there is a bacterial infection. However, it is not clear whether they add benefit beyond what is suggested in the recommendation on tests to help differentiate between viral and bacterial pneumonia to guide decisions about antibiotics. The most appropriate threshold for procalcitonin is also uncertain.