Is COVID-19 set to become endemic?

Covid-19 - endemic
Photo via Ricardo Huñis/Flickr (Public Domain)

As we enter the seventh month of the coronavirus pandemic, we still have much to learn about the virus. Even though we may be on the precipice of a vaccine, it might be time to come to terms with the fact that COVID-19 will be endemic, which means we will likely face it for years.

An endemic, for those unfamiliar with the terminology, is a disease or infection found among a population or geographic area that is constantly maintained at a baseline level. Common examples include the seasonal flu or common cold. In this scenario, the coronavirus would become perpetually found in specific communities, albeit at what would likely be a relatively low or predictable rate.

For a disease to be considered endemic, it requires a continuous reproduction number of (R) = 1, which means that each infected person transmits the virus to one other person. The basic reproduction number refers to the average number of people infected by coming into contact with just one person carrying the disease.

When the (R) is greater than 1, it indicates the spread of the disease is increasing. Less than 1 means the spread is decreasing through either control measures or herd immunity.

Because we don’t know yet how long a vaccination will stay effective or when exactly one will be ready for mass consumption, COVID-19 may seasonally mutate and require yearly vaccinations, much like influenza. We’re already seeing coronavirus reinfections that are worse the second time around, making this an ever more likely scenario. Also, the fact the U.S. keeps setting daily records for most new coronavirus cases is a problem.

In contrast, some endemic diseases, such as measles, provide permanent immunity after infection. Children are born susceptible, however, after maternal immunity wears off. This is why we have childhood immunizations to avoid entirely preventable future outbreaks.

Columbia University’s Mailman School of Public Health recently published an article that set out to determine whether the COVID-19 virus would become endemic by identifying crucial contributing factors to the transmission of the virus. These include risk for reinfection, both the availability and efficacy of a vaccine, seasonal reoccurrences, as well as interactions with other infections that could cause the virus to mutate.

The anecdotal evidence seems to suggest that COVID-19 is indeed headed toward becoming endemic.

“Should reinfection prove commonplace, and barring a highly effective vaccine delivered to most of the world’s population, SARS-CoV-2 will likely settle into a pattern of endemicity,” write the authors of the paper. “Whether reinfections will be commonplace, how often they will occur, how contagious re-infected individuals will be, and whether the risk of severe clinical outcomes changes with subsequent infection remains to be understood.”

The Bottom Line

The situation appears grim, but there is still much we don’t know about the coronavirus. How long immunity lasts, if at all, and how successful these forthcoming vaccines will be at treating the disease need to be understood before researchers can accurately predict anything.

If the infection becomes manageable and we can protect people from experiencing the most severe symptoms and outcomes of the disease, COVID-19 may end up as yet another virus that we learn to live with. Eventually, many people will experience less severe cases throughout their lifetimes.

It may be that we’ll eventually need annual coronavirus vaccinations, similar to the seasonal flu (and we must try to avoid a twindemic). Alternately, vaccinations may be administered at an “optimal age,” likely during childhood. Complete elimination or eradication of a disease is “notoriously difficult,” as the Conversation points out, adding credence to the theory that COVID-19 is likely here to stay.

Sources: The Conversation, Science Daily, CDC

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