Can my patient with Covid-19 get reinfected?

Patients with prior history of Covid-19 have been shown to get reinfected, sometimes less severe and sometimes more severe than the first bout.1-3 What we don’t really know is how often reinfection actually occurs, either with or without symptoms.

Symptomatic reinfection with genetically distinct SARS-CoV-2 following Covid-19 has been reported from several countries, including the USA. 1  A case series of 4 patients (age range of 33-51 y) found the severity of second infection ranging from asymptomatic to more severe disease requiring hospitalization.  First infection was mild in these cases with an intervening period of 48-142 days.1  BNO News, a Dutch website, lists many more “officially confirmed cases” as well as over a thousand “suspected reinfection cases”.4

Reinfection with Covid-19 in at least some people should not be too surprising. Some may have a suboptimal immune response to the first infection (eg with mild infection) that may be short-lasting, while others may have a better response.  Even in those with adequate response, SARS-CoV-2 antibodies may drop rapidly (half-life 36 days according to one study).3 Immunity to several other seasonal respiratory coronaviruses (cousins of SARS-CoV-2) also seems short lived (as short as 6 months).5 How much other arms of the immune system besides antibodies (eg, T cell immunity) play a role in conferring longer lasting immunity remains unclear.

These findings suggest that we cannot rely on natural infection to provide us individual or herd immunity.  Immunization is likely a better answer!

Bonus Pearl: Did you know that preliminary reports suggest that antibody loss with Covid-19 is more rapid than that found for SARS-CoV-1, the agent of SARS pandemic of 2003?3

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  1. Iwasaki A. What reinfections mean for COVID-19. Lancet Infect Dis 2020. Published online October 12, 2020.
  2. Tillett RL, Sevinsky JR, Hartley PD, et al. Genomic evidence for reinfection with SARS-CoV-2: a case study. Lancet Infect Dis 2020. Published online October 12, 2020.
  3. Ibarrondo J, Fulcher JA, Goodman-Meza D, et al. Rapid decay of anti-SARS-CoV-2 antibodies in persons with mild Covid-19. N Engl J Med 2020; September 10.
  4. Kunzman K. Contagion Live. October 12, 2020. Accessed Dec 23, 2020.
  5. Edridge AWD, Kaczorowska J, Hoste ACR, et al. Seasonal coronavirus protective immunity is short-lasting. Nature Medicine 2020;26:1691-93.

Disclosures: The listed questions and answers are solely the responsibility of the author and do not necessarily represent the official views of Mercy Hospital-St. Louis or its affiliate healthcare centers. Although every effort has been made to provide accurate information, the author is far from being perfect. The reader is urged to verify the content of the material with other sources as deemed appropriate and exercise clinical judgment in the interpretation and application of the information provided herein. No responsibility for an adverse outcome or guarantees for a favorable clinical result is assumed by the author. Thank you!



Can my patient with Covid-19 get reinfected?

Can my patient contract influenza more than once in a season?

It’s not common but reinfection with influenza can definitely occur, either due to the same viral strain, or due to a different one altogether.

One study reported influenza reinfection due to H1N1 in otherwise healthy patients within 12-20 days of the original infection after an apparent period of full recovery. 1 There was no evidence of resistance to oseltamivir among isolates and all patients recovered after the second infection.

Reinfection with the same viral strain within 2-3 weeks of the initial bout of influenza shouldn’t be too surprising since it takes 4-7 weeks for antibody response to the infection to peak. 2 Reexposure to the same circulating strain of influenza virus (the season can last 6 weeks or longer) can then result in reinfection when the body hasn’t had enough time to make significant amount of protective antibodies following the first infection.

Another explanation is that more than 1 strains of influenza virus often circulate during any given season.   This places patients at risk of infection due to strains of influenza virus that do not confer significant cross-immunity between each other,  resulting in getting “the flu twice in 1 season.” 3


  1. Perz CM, Ferres M, Labarca JA. Pandemic (H1N1) 2009 reinfection, Chile. Emerg Infect Dis 2010;16:156-57.
  2. Treanor JJ. Influenza viruses, including avian influenza and swine influenza. In: Mandell GL, Bennett JE, Dolin R, eds. Principles and practice of infectious diseases. 7th ed. New York: Elsevier; 2010. p 2265-2293.
  3. Rettner R. Can you get the flu twice in 1 season? Scientific American, LiveScience, February 4, 2018. . Accessed February 5, 2018.


Can my patient contract influenza more than once in a season?