Tuesday, September 29, 2020

C.I.D.: Another SARS-CoV-2 Reinfection Report - 2 HCWs From India



It was only 5 weeks ago that HKU Med Announced the 1st Documented Reinfection With SARS-CoV-2  in a 33 year-old Hong Kong man who had tested positive for SARS-CoV-2 last spring, and who  tested positive again after recently returning from a trip to Spain. 

Unlike earlier cases - which were often dismissed as `relapses' public health authorities had access to genetic sequencing information of both of this patient's infections, and were able to determine they were due to two genetically distinct viruses. 

Less than twenty-four hours later, two more reports emerged from Europe (see Two More Reports of SARS-CoV-2 Reinfection (Netherlands & Belgium) - followed a week later by another report from Nevada.  While the number of laboratory confirmed reinfections remains small, the availability of genetic sequence data is limited, making such determinations challenging. 

While many of these documented reinfections have presented asymptomatically, or with mild symptoms, this hasn't always been the case.  The Nevada patient's second illness  - mentioned above - was reportedly a significantly worse than the first, and was serious enough to require hospitalization. 

At the same time we've seen numerous reports of rapidly waning antibody titers in recovered COVID-19 patients, which also raises concerns over the duration and extent of protective immunity following infection (and potentially, vaccination)

This has been the topic of numerous blogs over the past few months, including:

Nature Medicine: Seasonal Coronavirus Protective Immunity Is Short-Lasting

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

Imperial College London: (REACT) SARS-CoV-2 Antibody Prevalence Study - England

COVID-19: From here To Immunity (Take Two)

Last July (see Kings College: Longitudinal Evaluation & Decline of Antibody Responses in SARS-CoV-2 infection), researchers reported that `the magnitude of the nAb response is dependent upon the disease severity', something we'd seen previously with MERS-CoV (see EID Journal: Antibody Response & Disease Severity In HCW MERS Survivors).

They also found a significant percentage of mild cases saw their nAb titers drop to near baseline within 60 days post-infection.
It should be noted that nAb titers aren't the only measure of potential post-infection immunity, as the role of T-Cells and other elements of the innate immune system in fighting this virus are poorly understood. 

How common - or clinically significant - reinfection really is among recovered COVID-19 patients is unknown, but it is obviously a concern for vaccinologists who hope to launch a SARS-COV-2 vaccine early next year. 

All of which brings us to another very brief report, published last week in Clinical Infectious Diseases which describes two Health Care Workers (25 M , 28 F) in India who had laboratory confirmed (asymptomatic) SARS-CoV-2 infection last May, and who subsequently tested positive again in mid-August and early September. 

Since all of their infections were asymptomatic, their discovery was somewhat fortuitous, leading the authors to suggest that reinfections are potentially under-reported occurrences.   Follow the link to read the report in full. 

Asymptomatic reinfection in two healthcare workers from India with genetically distinct SARS-CoV-2 

Vivek Gupta, Rahul C Bhoyar, Abhinav Jain, Saurabh Srivastava, Rashmi Upadhayay, Mohamed Imran, Bani Jolly, Mohit Kumar Divakar, Disha Sharma, Paras Sehgal 

Clinical Infectious Diseases, ciaa1451, https://doi.org/10.1093/cid/ciaa1451
Published: 23 September 2020 


While it is becoming increasingly apparent that re-infection can occur with SARS-COV-2 - how often that happens - and how much of a real-world impact it may have on the course and duration of our COVID-19 pandemic remains unknown.

For now, these scattered reports of reinfection are more cautionary signs than warning klaxons.

But we are still very early in this pandemic, surveillance for reinfections is spotty at best, and our understanding of the interaction between SARS-COV-2 and the human immune system is far from complete.  

All of which makes reports like these very much worth our attention.