There are several side effects of COVID-19, many of which are short-term and subside within a few days or weeks of recovering. However, there are some instances where symptoms linger and have yet to go away for people who have long-recovered from the virus.

New research indicates that there 55 long-term side effects associated with COVID-19. It's important to note that the systematic review and meta-analysis, of which nearly 48,000 people who had COVID-19 were included, has yet to be peer-reviewed. This means the new medical research has yet to be evaluated and shouldn't be used to guide clinical practice. Still, the findings are telling and may even help to validate your own suspicions. (Related: The One Vitamin Doctors Are Urging Everyone to Take Right Now).

The participants studied were between the ages of 17 and 87, and an estimated 80% of them report that they developed at least or more long-term side effects after contracting COVID-19. Of the 55 long-term side effects, the five most common include fatigue, with 58% reporting this symptom has sustained, headache (44%), attention disorder (27%), hair loss (25%), and dyspnea, or difficultly breathing (24%). However, an estimated 21% report they are still struggling with anosmia, which is the partial or complete loss of smell.

The patient follow-up time ranged from 14 to 110 days, in the 15 studies that were selected (of 18,251 that were screened) for this systematic review. For example, the most common long-term side effect, fatigue, was found to be present 100 days after a person's first symptom of acute COVID-19. The reason for these sustained side effects may have to do with residual inflammation.

The reason why people lose their sense of taste and smell at the onset of being infected with the SARS-CoV-2 virus may be attributable to inflammation in the blood vessels, which are responsible for distributing blood all throughout the body.

As Brittany Busse, MD, associate medical director of WorkCare explains to Eat This, Not That!, the virus can cause inflammation to show up in the lungs, in the brain, and essentially all over the body, largely because blood vessels are found in every single organ.

"COVID is essentially the body's response to the SARS-CoV-2 virus. So, COVID is the syndrome, SARS-CoV-2 is the virus. And the syndrome's severity will be based on how much inflammation your body creates in response to the virus," she says.

Busse adds that the loss of taste and smell is mediated by a nerve and if the blood vessels are inflamed, it could shock that nerve into not working. "It has some kind of neurologic inflammation associated with it as well," she says.

So, if your sense of smell has yet to be fully restored, know that you're not alone. Until this systematic review is peer-reviewed and more research is conducted, consider upping your intake of inflammation-fighting vitamins such as B6, K2, and D. Before taking any supplements, be sure to consult your doctor first.

For more, consider reading 8 Ways to Support a Healthy Immune System, According to Harvard.