#15,833
Of course, reinfection wasn't the only possible explanation. It is possible that the tests used to clear her for discharge simply weren't sensitive enough to pick up a lingering, low grade, infection. In that case, this could have been a relapse, not a reinfection.
But over the past 12 months we've seen a small number of other cases where reinfection has been established, often among COVID patients who reportedly had a mild first bout of the virus. A few examples include:
Meanwhile, last summer and fall we saw a number of studies and cautionary statements from public health agencies, on the uncertainty of prolonged post-infection SARS-CoV-2 immunity.
Almost exactly a year ago, in Osaka Japan: `Recovered' Patient Tests Positive For COVID-19, we saw the first inkling that infection and recovery from COVID-19 might not produce robust and long lasting immunity.
The patient, a tour bus guide in Osaka - who was hospitalized with COVID-19 in late January, 2020 and released from the hospital on Feb. 6th after testing negative - tested positive again 3 weeks later.
Of course, reinfection wasn't the only possible explanation. It is possible that the tests used to clear her for discharge simply weren't sensitive enough to pick up a lingering, low grade, infection. In that case, this could have been a relapse, not a reinfection.
But over the past 12 months we've seen a small number of other cases where reinfection has been established, often among COVID patients who reportedly had a mild first bout of the virus. A few examples include:
With the exception of the Nevada case (mentioned above), reinfection was generally reported to be mild or even asymptomatic. While reinfections are only rarely documented - laboratory confirmation can be quite difficult - and so many probably go unreported.
EID Journal: Antibody Profiles According to Mild or Severe SARS-CoV-2 Infection
CDC Clarifies: Recovered COVID-19 Cases Are Not Necessarily Immune To Reinfection
Kings College: Longitudinal Evaluation & Decline of Antibody Responses in SARS-CoV-2 infection
More recently, with the rise of new variants we are seeing increasing - albeit often anecdotal - evidence of increased rates of reinfection in hard hit places like South Africa and Brazil (see Brazil MOH Confirms Reinfection With COVID Variant P.1 In Amazonas and The Lancet: Resurgence of COVID-19 in Manaus, Brazil, Despite High Seroprevalence).
How big of an obstacle this may be in achieving herd immunity and ending this pandemic is unknown, as is how much more (or less) protective a vaccine may be over natural infection.
There is also likely a wide range of post-infection immune responses across the population - due to age, immune competence, individual genetics, medications and comorbidities - with some people acquiring far more robust and longer-lasting immunity than others.
Adding to our limited data on reinfection, yesterday the CDC's MMWR published a report on suspected repeat infections among five elderly residents of a SNF in Kentucky. Unlike with many previous reports, all five experienced more severe illness the second time around.
I've only reproduced the summary, and some excerpts from a much longer report. So follow the link to read it in its entirety.
Suspected Recurrent SARS-CoV-2 Infections Among Residents of a Skilled Nursing Facility During a Second COVID-19 Outbreak — Kentucky, July–November 2020
Weekly / February 26, 2021 / 70(8);273–277
Alyson M. Cavanaugh, DPT, PhD1,2; Douglas Thoroughman, PhD1,3; Holly Miranda1,4; Kevin Spicer, MD, PhD1,5
What is already known about this topic?
Case reports of reinfection with SARS-CoV-2 exist; however, data are limited as to the frequency and outcomes of reinfection.
What is added by this report?
Five residents of a skilled nursing facility received positive SARS-CoV-2 nucleic acid test results in two separate COVID-19 outbreaks separated by 3 months. Residents received at least four negative test results between the two outbreaks, suggesting the possibility of reinfection. Severity of disease in the five residents during the second outbreak was worse than that during the first outbreak and included one death.
What are the implications for public health practice?
Skilled nursing facilities should use strategies to reduce the risk for SARS-CoV-2 transmission among all residents, including among those who have previously had a COVID-19 diagnosis. Vaccination of residents and health care personnel in this setting is particularly important to protect residents.
Reinfection with SARS-CoV-2, the virus that causes coronavirus disease 2019 (COVID-19), is believed to be rare (1). Some level of immunity after SARS-CoV-2 infection is expected; however, the evidence regarding duration and level of protection is still emerging (2).
The Kentucky Department for Public Health (KDPH) and a local health department conducted an investigation at a skilled nursing facility (SNF) that experienced a second COVID-19 outbreak in October 2020, 3 months after a first outbreak in July. Five residents received positive SARS-CoV-2 reverse transcription–polymerase chain reaction (RT-PCR) test results during both outbreaks. During the first outbreak, three of the five patients were asymptomatic and two had mild symptoms that resolved before the second outbreak.
Disease severity in the five residents during the second outbreak was worse than that during the first outbreak and included one death. Because test samples were not retained, phylogenetic strain comparison was not possible. However, interim period symptom resolution in the two symptomatic patients, at least four consecutive negative RT-PCR tests for all five patients before receiving a positive test result during the second outbreak, and the 3-month interval between the first and the second outbreaks, suggest the possibility that reinfection occurred.
Maintaining physical distance, wearing face coverings or masks, and frequent hand hygiene are critical mitigation strategies necessary to prevent transmission of SARS-CoV-2 to SNF residents, a particularly vulnerable population at risk for poor COVID-19–associated outcomes.* Testing, containment strategies (isolation and quarantine), and vaccination of residents and health care personnel (HCP) are also essential components to protecting vulnerable residents. The findings of this study highlight the importance of maintaining public health mitigation and protection strategies that reduce transmission risk, even among persons with a history of COVID-19 infection.
(SNIP)
Five SNF residents received positive SARS-CoV-2 test results during two separate facility outbreaks that occurred in July and October 2020, suggesting possible reinfection. Affected persons experienced more severe illness during their second SARS-CoV-2 infection. Reinfection risk to the general population is suspected to be low, but SNF residents might have higher risk for new exposures, given the congregate nature of these settings and ongoing interactions with HCP and other residents.
In addition, the level and duration of postinfection immunity in persons with an aging immune system is unknown, but the potential health consequences of reinfection among SNF populations remain serious. Therefore, steps to protect this population from the ongoing potential of SARS-CoV-2 exposures should be implemented.
Based on the observations of this study, testing and cohorting practices in SNFs should not assume that residents infected >90 days earlier are immune to COVID-19. Public health interventions to limit transmission are vital for all persons in SNFs, including those who have previously been infected with SARS-CoV-2; these include physical distancing, use of masks (including by SNF residents, if tolerated), and frequent hand hygiene using hand sanitizer with 60%–95% alcohol or washing with soap and water for at least 20 seconds. Vaccination in these settings, as recommended by the Advisory Committee on Immunization Practices, is particularly important to optimally protect these vulnerable persons (10).
While those who are infected with, and recover from, SARS-CoV-2 likely carry some degree of acquired immunity, how long that will last, and how effective it will be against a growing array of variants, is unknown.
Today's study is a reminder that even if you've had and recovered from COVID, the usual precautions of social distancing, wearing face covers in public, and getting vaccinated when it is offered still apply.
