How likely are you to get COVID-19 twice?

Even recovered patients need to practice good public health practices to avoid reinfection

There is a lot of information circulating about COVID-19 and how atrisk you are for infection. You might understand how likely you are to get COVID-19 based on your vaccination status, but how likely are you to get COVID-19 twice? Due to the novelty of this virus, details surrounding the possibility of reinfection are still being investigated. However, it is important to understand how long immunity can last post-infection, so you can take appropriate measures.

For some viruses, an initial infection can provide lifelong immunity; however, seasonal viruses like COVID-19 offer short-term protection. The production of antibodies, triggered either through direct COVID-19 infection or vaccination, are a part of the body’s immune response. The activation of these antibodies results in immunity against the virus, keeping you safe. Immunoglobulins, specifically IgM and IgG antibodies, are detected as a sign of the immune response. A study investigating the length of immunity in patients who have recovered from COVID-19 demonstrated that IgG antibodies and memory B and T cells persisted for at least three months post-recovery. The study further revealed that SARS-CoV-2 specific IgG memory B cells increased over time. However, previous studies have demonstrated that cured patients can continue to be viral carriers for a certain period of time, for up to two weeks post-recovery. Researchers have also speculated that the

SARS-CoV-2 virus can remain longer in certain tissues such as digestive tissue, as compared to the respiratory tract. In addition, recovered patients have also demonstrated that they can continue to spread the virus post-recovery.

Past studies on other respiratory illnesses report that reinfection may be unlikely; however, this data is still under investigation. Moreover, a small number of recovered patients have reported having caught COVID-19 for a second time post-recovery. A study from early in the pandemic by Public Health England indicated that antibodies provided 83 per cent protection against COVID-19 reinfections over a five-month period. While most of the reported reinfections were milder than the initial infections, some were more harmful, with a few individuals dying as a result. Researchers are stating that individuals who experienced mild symptoms in their initial infection have a higher risk of reinfection because they did not develop a proper immune response the first time. This is also true for individuals who are immunosuppressed and did not have an immune response to the initial infection either.

Additionally, the new COVID-19 mutations and variants offer an opportunity that may further complicate the risk of reinfection. Reinfections may be more likely with the new viral strains, specifically the B.117 variant which originated in the U.K. A pre-print article tracking the infectiousness of the variant originating in Brazil, indicated that it eluded the human immune response, which was triggered by the previous variants. Therefore, reinfection with a variant strain is both possible and likely. The mechanism behind reinfection with a variant strain is that the viral strain can change to the point where an individual’s immune system does not recognize it and does not produce a protective immune response.

Understanding the duration of the immune response elicited by SARS-CoV-2 infection is significant. Future studies reporting immunity length and investigating cases of reinfection in recovered COVID-19 patients will shed more light on this important topic. However, given the current understanding of short-term immunity in recovered COVID-19 patients, there is still a potential risk of reinfection; therefore, recovered patients should be educated on this risk. Future directions on this topic should also conduct a long-term investigation of the differences in immunity length in vaccinated individuals versus individuals who have recovered from COVID-19. Pareesa Ali is a student in the Faculty of Science at McMaster University. She is a passionate researcher and writer, with a focus on health and medicine. Jasrita Singh is a student in the Faculty of Health Sciences at McMaster University, specializing in biomedical discovery and commercialization. Her research interests are in translational medicine and synthetic biology. Austin Mardon, PhD, CM, FRSC, is an adjunct professor in the Faculty of Medicine and Dentistry at the University of Alberta, an order of Canada member, and fellow of the Royal Society of Canada.