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ECDC Technical Rpt: Reinfection with SARS-CoV-2 (Surveillance Case Definition)

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  • ECDC Technical Rpt: Reinfection with SARS-CoV-2 (Surveillance Case Definition)

    ECDC Technical Rpt: Reinfection with SARS-CoV-2 (Surveillance Case Definition)


    A year ago, in COVID-19: From Here To Immunity, we looked at the growing concerns that COVID-19 might not be a one-and-done infection like measles or chickenpox - and instead be more akin to influenza - which not only mutates over time but often leaves behind less than permanent immunity.

    Infections with hCoV (human coronaviruses) were already known to be recurrent, and studies on MERS-CoV survivors had shown waning antibody levels (see EID Journal: Antibody Response & Disease Severity In HCW MERS Survivors), particularly among those with mild illness.

    And less than a year earlier, in 2019's C.I.D.: Influenza A Reinfection in Sequential Human Challenge, we'd seen the surprising results of an NIH influenza challenge study suggesting reinfection with exactly the same strain of influenza A was not only possible, it might even be common.

    The authors (including David M. Morens, MD & Jeffery K. Taubenberger MD, PhD) wrote:


    The data presented in this report demonstrate that sequential infection with the identical influenza A virus can occur and suggest it may not be rare. These data raise questions about immune memory responses in an acute superficial respiratory mucosal infection and their implications in development of broadly protective influenza vaccines. Further investigation of these observations is warranted

    And by April of 2020, barely 3 months into the global outbreak, we'd already seen anecdotal reports of suspected reinfection with COVID-19 (see Osaka Japan: `Recovered' Patient Tests Positive For COVID-19), although many doctors believed they were more likely the result of a relapse than a reinfection.

    For many officials, hopes of ending this pandemic quickly were based on rapidly achieving `herd immunity' (see GAO: A Herd Immunity For COVID-19 Primer), possibly using antibody tests to issue `immunity passports' to get people back to work (see WHO Scientific Brief: `Immunity Passports' For COVID-19).

    Making any talk of reinfections - or worse - of mutations in the virus (see COVID-19 & The `M' Word), unwelcome in certain circles.

    But by last fall, the impact and significance of the D614G mutation was widely accepted (see Study: SARS-CoV-2 D614G Variant Exhibits Efficient Replication Ex Vivo and Transmission in Vivo), and we'd begun to see a small number of laboratory confirmed reinfections with SARS-COV-2 (see Another SARS-COV-2 Reinfection Report To Ponder (Nevada, United States).

    Reinfections, we were assured, were rare and the SARS-CoV-2 virus was remarkably stable. While hundreds of mutations had been identified, none were considered significant, or likely to impact transmission, virulence, or immune escape.

    Cracks in this narrative began to appear last November, when Denmark announced the detection of - and spread in humans - of a `mink variant' of COVID-19, which escaped local mink farms (see Denmark Orders Culling Of All Mink Following Discovery Of Mutated Coronavirus).

    While the mink variant didn't prove to be as big of a problem as originally feared, in mid-December the wheels fell off with the announcement of a `more transmissible' B.1.1.7 variant in the UK.

    Since then the number of VOCs (variants of concern) has risen sharply (see UK PHE Now Tracking 9th Variant), with some exhibiting increased severity (see NERVTAG Report On Increased Severity With COVID Variant B.1.1.7), and others (like P.1 and B.1.351) showing signs of reduced antibody recognition, increasing the risks of reinfection or vaccine escape.

    Over the past couple of months we've seen a substantial increase in verified reports of reinfection with COVID, although no one really knows how big of a problem this is, or will become. A few examples:
    As we've discussed often, verifying reinfection with SARS-CoV-2 is often difficult or impossible due to a lack of genomic testing, and in some cases, even RT-PCR testing results. There has been no uniform case definition to help identify COVID reinfections, and often no requirement to report suspected or confirmed reinfections.

    In an attempt to provide some uniformity, and guidelines, for EU/EEA nations to recognize and report reinfections, the ECDC has today released a 10-page technical report with case definitions and testing requirements.

    The link to the full report, and the executive summary, are reproduced below, along with a couple of snippets from the report. Follow the link to read it in its entirety.
    Technical report

    8 Apr 2021

    The aim of this document is to present the findings of a survey of EU/EEA countries carried out to ascertain surveillance practices implemented to document and report suspected reinfection cases. In addition, this document summarises the available evidence on the duration of protective immunity following infection with SARS-CoV-2, addressing concerns related to reinfection, such as disease severity during a reinfection episode. The survey responses and available evidence are used to underline the rationale for the surveillance case definition proposed for suspected reinfection cases, to be reported via The European Surveillance System (TESSy).

    Executive summary

    Key messages
    • Reinfection with SARS-CoV-2 has been reported both within the European Union/European Economic Area (EU/EEA) and globally. This report summarises the available evidence about reinfection and duration of immunity following SARS-CoV-2 infection and describes surveillance practices implemented in EU/EEA countries to document and report suspected reinfection cases.
    • Thirteen of 17 EU/EEA countries responding to a survey sent by ECDC on 28 January 2021 about existing surveillance case definitions and reporting systems for reinfection confirmed they had a national case definition, with the minimum interval between episodes described in the definition ranging from 45 to 90 days. In terms of diagnostic testing criteria, countries report different practices for identifying and counting possible SARS-CoV-2 reinfection cases.
    • In 2020, a total of 1 887 possible cases of reinfection were reported to be under investigation across 12 responding EU/EEA countries.
    • SARS-CoV-2 variants of concern – in particular B.1.351 and P.1 – have demonstrated a capacity to escape protective immune responses mounted by individuals that have recovered from a prior infection. It is possible that reinfections may occur more frequently in areas where there is sustained transmission of these new variants.
    • Although reinfection events are rare, they are likely under-reported. In order to better ascertain the burden and impact of SARS-CoV-2 reinfection across the EU/EEA, particularly in the context of emerging variants with immune escape potential, ECDC has established a surveillance case definition for suspected reinfection, introducing new case-based and aggregated variables to improve systematic reporting via The European Surveillance System (TESSy).

    Reinfection with SARS-CoV-2: implementation of a surveillance case definition within the EU/EEA- EN - [PDF-860.08 KB]


    Risk posed by emerging SARS-CoV-2 variants

    Since April 2020, the emergence of a SARS-CoV-2 variant circulating in mink has highlighted the ability of the virus to adapt in animal species, while retaining transmissibility and pathogenicity among humans [23]. In February 2021, ECDC published a Rapid Risk Assessment focussing on the emergence and increased spread of new SARSCoV-2 VOCs first identified in the United Kingdom (B.1.1.7), South Africa (B.1.351), and Brazil (P.1) [24]. All three variants have demonstrated increased transmissibility in human populations, with B.1.1.7 associated with increased disease severity. While seroconversion to previously circulating SARS-CoV-2 strains may generate neutralising antibodies that protect against reinfection by a homologous virus, the neutralising capacity of these antibodies is reduced against VOCs, particularly those bearing the E484K mutation [24,25].



    While reinfection events appear to be rare, there is currently limited population level data available that captures the burden of reinfection cases at national level and over time. Following a survey of EU/EEA countries, the majority of responding countries reported having a working case definition and a national reporting system to capture reinfection cases. These definitions, although similar, were not standardised. In order to better ascertain the burden and impact of SARS-CoV-2 reinfection across the EU/EEA, particularly in the context of emerging variants with immune escape potential, ECDC has established a surveillance case definition for suspected reinfection, introducing new case-based and aggregate variables to improve systematic reporting via The European Surveillance System (TESSy).
    All medical discussions are for educational purposes. I am not a doctor, just a retired paramedic. Nothing I post should be construed as specific medical advice. If you have a medical problem, see your physician.