As COVID-19 continues to wreak havoc across the world, doctors question whether immunity to SARS-CoV-2 can be long-lasting and, if there’s a risk of re-infection. Previously it was believed that antibodies produced after infection may provide immunity to COVID-19 and protect a person from getting re-infected. However, research has proven that these antibodies only last two to three months in most individuals.
In the past, there have been multiple reports of people testing positive for the virus a second time despite testing negative earlier. Researchers argue that this is likely due to the viral fragments that people continue to shed for weeks after recovery and not because of re-infection. However, as no viral genome sequencing was conducted it is hard to differentiate whether these are cases of re-infection or just virus shedders.
Researchers at the University of Hong Kong (HKU) have reported the first documented case of human re-infection by SARS-CoV-2 using viral genome analysis. According to the research due to be published in the journal Clinical Infectious Diseases, the 33-year-old first contracted the infection in March. A positive SARS-COV-2 RT-PCR test confirmed his diagnosis and by April 14th he was discharged from the hospital after two negative PCR tests.
The second episode occurred 142 days after the first symptomatic episode. On August 15th, after returning from Spain via the United Kingdom, a screening test at Hong Kong airport found him to be positive for the novel coronavirus. The 33-year-old however, remained asymptomatic.
To confirm whether this was a case of re-infection or, viral shedding from the previous infection, researchers at HKU conducted genome analysis on the respiratory specimens collected during both episodes. The genomic analysis showed a total of 24 nucleotide difference in the two specimens, suggesting that the first viral strain was completely different than that from the second episode. They also found elevated levels of CRP and seroconversion of SARS-CoV-2 IgG antibodies during the second episode, proving that it was an acute infection.
The findings of the study, therefore, imply that herd immunity will unlikely eliminate SARS-CoV-2 as COVID-19 will likely continue to circulate in the human population, much like the seasonal coronaviruses. Secondly, vaccines will unlikely to provide lifelong immunity against COVID-19. Therefore, further studies on re-infection are required to develop more effective vaccines against the virus.
Recently, scientists at the University of Nevada, Reno School of Medicine, reported a likely case of re-infection in a 25-year-old man who had tested positive twice. Genome sequencing of the patient’s samples showed a significant genetic difference suggesting that the man had been re-infected.
As alarming as these findings are, it is important to remember that re-infection is still a rare occurrence. The World Health Organization, therefore, does not want you jumping to conclusions just yet.
As we continue to learn more about the novel coronavirus, it is important to keep on wearing masks and practicing social distancing, irrespective of whether we have previously been infected or not.
To, Kelvin Kai-Wang, et al. “COVID-19 Re-Infection by a Phylogenetically Distinct SARS-Coronavirus-2 Strain Confirmed by Whole Genome Sequencing.” Clinical Infectious Diseases, 2020, doi:10.1093/cid/ciaa1275.
Long, Q., Tang, X., Shi, Q. et al. Clinical and immunological assessment of asymptomatic SARS-CoV-2 infections. Nat Med 26, 1200–1204 (2020). https://doi.org/10.1038/s41591-020-0965-6
Nevada State Public Health Lab-led team studying COVID-19 reinfection. (n.d.). Retrieved August 30, 2020, from https://www.unr.edu/nevada-today/news/2020/covid-reinfection-study