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COVID-19 Reinfection in Elders

 Elders at Higher Risk of COVID-19 Reinfection

    If someone has received a COVID-19 vaccine or been infected with the virus, does this prevent them from reinfection? According to the Centers for Disease Control and Prevention, "cases of reinfection with COVID-19 have been reported, but remain rare." As of March 21, 2021, a Dutch news site that has been tracking repeat infection confirms 66 worldwide cases of coronavirus reinfection, or instances where individuals are infected with COVID-19 for a second (or more) time(s). Understanding the degree of protection against COVID-19 reinfection is important to develop effective strategies in mitigating coronavirus infection rates. A study conducted in Denmark and published in The Lancet on March 17, 2021 used COVID-19 data to estimate the protection towards COVID-19 reinfection.

About the Study

    Individual-level data was collected from the Danish Microbiology Database for individuals who had a COVID-19 PCR, or polymerase chain reaction, test between February 26 and December 31, 2020. Researchers compared COVID-19 infection rates of individuals in the first surge from March-May 2020, to that of individuals in the second surge from September-December 2020. By December 31, 2020, 3.96 million individuals in Denmark had been tested; researchers focused on the data of those who tested positive.

Study Results

   Of all those who were tested in the first surge, 535,339 individuals remained in follow-up for the second surge. Of these individuals, 2.11% tested positive in the first surge and 0.65% of those who tested positive in the first surge tested positive again in the second surge. In comparison, 3.27% of people who tested negative in the first surge tested positive in the second surge. These numbers confirm the possibility of getting reinfected with COVID-19 but show that there is a decreased chance of reinfection (0.65%) compared to initial infection (2.11%).

    The main findings of the study, however, is the difference in potential against repeat infection between age groups. Researchers found out that about 6 months after initial infection, the estimated protection against reinfection was about 80% in individuals under the age of 65. On the other hand, for individuals over 65 years and older, the protection against reinfection dropped to 47% although no difference of reinfection rates between men and women were observed. In other words, elders are at a significantly higher risk of COVID-19 reinfection. 

Explanations and Implications

   Researchers have proposed a couple reasons as to why elders are at a higher risk of getting COVID-19 more than once. The results could be explained by "natural-age related changes in the immune system of older adults." These changes result in elders being more susceptible to infectious diseases like the coronavirus. Another possible result of these changes is the disruption of T-cell coordination in elders and "scarcity of T-cells [which have been] associated with aging and worse COVID-19 outcomes." T-cells play an important role in immunity as they kill infected cells which replicate the virus; thus, a lack of T-cells and T-cell coordination could prove to be detrimental in fighting off the virus and developing immunity.

    The new findings from this study highlight the importance of protecting older people against COVID-19 reinfection. Measures can be taken to prioritize this group for vaccinations and enhance social distancing and infection control.

Sources

  1. Hansen, Christian Holm, et al. “Assessment of Protection against Reinfection with SARS-CoV-2 among 4 Million PCR-Tested Individuals in Denmark in 2020: a Population-Level Observational Study.” The Lancet, 17 Mar. 2021, doi:https://doi.org/10.1016/S0140-6736(21)00575-4.
  2. “Reinfection with COVID-19.” Centers for Disease Control and Prevention, Centers for Disease Control and Prevention, www.cdc.gov/coronavirus/2019-ncov/your-health/reinfection.html.
  3. BNO News. “COVID-19 Reinfection Tracker.” BNO News, 21 Mar. 2021, bnonews.com/index.php/2020/08/covid-19-reinfection-tracker/.

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