Understanding Coinfection: What It Is and How Vaccination Can Help

During the on-going COVID-19 pandemic, coinfections with other pathogens have been observed in some patients and linked to worse outcomes. Understanding what a coinfection is may help to improve treatment and prevention.

Coinfection happens when the body is infected by multiple pathogenic species (bacteria, viruses, fungi, etc.) concurrently or consecutively. For example, a child who has influenza also gets a pneumococcal infection at the same time. Other terms used to identify coinfection include multiple infection, concurrent infection, simultaneous infection and polymicrobial.

Types of coinfection

There are three types of coinfection:

  • Concurrent acute infection: When multiple infections occur at the same time. One of the more common concurrent infections is the influenza-pneumococcal coinfection. The body is more susceptible to a respiratory bacterial infection during a viral infection. During the COVID-19 pandemic, there have been reports of varied cases of SARS-CoV-2 coinfection with other respiratory pathogens. There can also be coinfection of dengue with mycoplasma infection. Other combinations are also possible.
  • Secondary/sequential infection: After the initial infection has subsided, a secondary infection may follow due to a suppressed immune system. A common example is otitis media, a ear infection usually caused by S. pneumonia or H. influenza, which often occurs after a respiratory syncytial virus (RSV), coronavirus or adenoviral infection. This delayed secondary infection is also referred to as a superinfection.
  • Concurrent with chronic infection: An underlying chronic infection can also lead to coinfection. Seen in HIV infection which impairs the immune system, the body becomes more susceptible to opportunistic pathogens, such as the tuberculosis-causing Mycobacterium tuberculosis. Indeed, HIV-tuberculosis coinfection has been a major contributor to the rise of global tuberculosis infection.

Worse complications

Compared with single infections, coinfections result in poorer health outcomes and tend to exacerbate infections.

An infection with influenza followed by pneumococcus could lead to a fatal outcome. Animal studies showed damage to the airways by influenza, allowing fatal secondary infection with pneumococcal.

Even if they survive, patients of coinfection may suffer severe long-term effects such as blindness, chronic diarrhoea, chronic inflammation, carcinoma, immunosuppression, liver fibrosis, meningitis, renal failure and rheumatic fever.

Coinfection also complicates treatment when it involves different pathogens, e.g. bacteria and virus. Antivirals or antibiotics are typically used to treat either viral or bacterial infections, but the effect of these medications on concurrent infections is still unclear.

Unknown underlying interactions may reduce treatment efficacy or even aggravate the coinfection. It is crucial to understand these specific interactions to identify suitable treatment strategies.

Vaccination as a better option

In most cases, prevention through vaccination is the recommended option. Many studies on influenza-pneumococcus coinfection have highlighted the potential of pneumococcal vaccination, in addition to an annual influenza vaccination, as a key strategy to reduce mortality and morbidity during an influenza outbreak.

One study also suggested pneumococcal and Haemophilus influenzae type b (Hib) vaccination as a viable supplementary strategy to reduce secondary coinfections in COVID-19 cases after finding a strong correlation between higher rates of pneumococcal vaccination in nations and cities with lower COVID-19 morbidity and mortality. Other coinfection cases may also benefit from vaccination against any of the pathogens involved. However, more research is required to understand specific coinfections.

Even if pneumococcal vaccination does not provide direct protection against influenza or COVID-19 coinfections, it will reduce hospital visits and admissions, and decrease the burden on healthcare resources.

A final note

Being infected by one disease is unpleasant enough; a second infection due to the first one is so much worse. Hence, it’s always wise to provide your child with greater protection against infections. The inclusion of pneumococcal vaccination in the National Immunisation Programme is a welcome step towards providing better healthcare for the nation. A more comprehensive vaccination course would ensure that you, your family and those at risk are better protected against infections and possible coinfections.

An educational contribution by Malaysian Paediatric Association.

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