When it emerged, SARS-CoV-2 was considered a novel virus, meaning it had not been seen in humans before. Since the virus was new, people’s immune systems had no memory or prior immunity to it. This is one of the reasons why the virus spread so quickly though people at first.

Once exposed to SARS-CoV-2, either through infection “out-in-the-wild” or a COVID-19 vaccine, the immune system can learn to recognize and respond to the virus. Immune cells called B cells, produce antibodies that recognize SARS-CoV-2. These antibodies can bind to the virus and help the immune system eliminate it. Some B cells become memory B cells, allowing the immune system to respond more quickly if it encounters the virus again.

Sometimes when the immune system is trying to protect us, it can induce a powerful but dysregulated attack called a cytokine storm. This is an overreaction by the immune system where it releases many inflammatory signals, called cytokines. The intense inflammation caused by the cytokine storm can damage healthy tissue and make illness more severe. While not specific to COVID-19, cytokine storms can happen in response to SARS-CoV-2 and scientists have been learning more about them since the virus emerged.

What is Long COVID?

Some people experience chronic symptoms for months after their initial SARS-CoV-2 infection. This is called long COVID and can develop after both mild and severe illness. Symptoms can include fatigue, brain fog, shortness of breath, and weakness. However, over 200 symptoms have been associated with long COVID. Researchers don’t know exactly what causes long COVID, but the immune system likely plays a role.

Researchers have found evidence of ongoing inflammation and changes in immune cell activity in people with long COVID, suggesting that the immune response may continue despite the initial infection being over. One reason the immune system may remain active is that remnants of the virus may remain in the body and continue to stimulate the immune system. Another reason may be that the infection triggers an autoimmune response, in which the immune system mistakenly attacks the body’s own tissues. While many questions remain unanswered, ongoing research is helping to uncover how immune system dysregulation may drive long COVID and guide the development of future treatments.

COVID-19 and mRNA Vaccines

Scientists had been studying mRNA technology for decades, but the COVID-19 pandemic accelerated its use and brought it into widespread public awareness. mRNA stands for messenger ribonucleic acid, referring to the type of RNA that carries instructions to make proteins.

A COVID-19 mRNA vaccine gives your cells instructions for how to make a specific protein found on the surface of SARS-CoV-2. After vaccination, nearby cells use the mRNA instructions to temporarily produce the protein. The immune system recognizes the protein as foreign and begins building an immune response. The protein on its own does not cause disease but is enough to train the immune system to fight SARS-CoV-2. Now, if you do encounter the whole virus, your immune system is prepared to respond.

mRNA vaccines are incredibly flexible, which means it is easy to update the mRNA in the vaccine to match changes in the virus as new SARS-CoV-2 strains emerge. Research during and since the COVID-19 pandemic demonstrated that mRNA vaccines are safe and effective. Researchers are now exploring how mRNA technology can be used against other infectious diseases, including influenza, Ebola, and HIV. Scientists are also investigating its use in cancer treatment and other immune-related conditions.