Reinfection by the SARS-CoV-2 Gamma variant in blood donors in Manaus, Brazil

  1. Carlos A. Prete
  2. Lewis F. Buss
  3. Renata Buccheri
  4. Claudia M. M. Abrahim
  5. Tassila Salomon
  6. Myuki A. E. Crispim
  7. Marcio K. Oikawa
  8. Eduard Grebe
  9. Allyson G. da Costa
  10. Nelson A. Fraiji
  11. Maria do P. S. S. Carvalho
  12. Charles Whittaker
  13. Neal Alexander
  14. Nuno R. Faria
  15. Christopher Dye
  16. Vítor H. Nascimento
  17. Michael P. Busch
  18. Ester Cerdeira Sabino

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Abstract

Background

The city of Manaus, north Brazil, was stricken by a second epidemic wave of SARS-CoV-2 despite high seroprevalence estimates, coinciding with the emergence of the Gamma (P.1) variant. Reinfections were postulated as a partial explanation for the second surge. However, accurate calculation of reinfection rates is difficult when stringent criteria as two time-separated RT-PCR tests and/or genome sequencing are required. To estimate the proportion of reinfections caused by Gamma during the second wave in Manaus and the protection conferred by previous infection, we identified anti-SARS-CoV-2 antibody boosting in repeat blood donors as a mean to infer reinfection.

Methods

We tested serial blood samples from unvaccinated repeat blood donors in Manaus for the presence of anti-SARS-CoV-2 IgG antibodies using two assays that display waning in early convalescence, enabling the detection of reinfection-induced boosting. Donors were required to have three or more donations, being at least one during each epidemic wave. We propose a strict serological definition of reinfection (reactivity boosting following waning like a V-shaped curve in both assays or three spaced boostings), probable (two separate boosting events) and possible (reinfection detected by only one assay) reinfections. The serial samples were used to divide donors into six groups defined based on the inferred sequence of infection and reinfection with non-Gamma and Gamma variants.

Results

From 3655 repeat blood donors, 238 met all inclusion criteria, and 223 had enough residual sample volume to perform both serological assays. We found 13.6% (95% CI 7.0–24.5%) of all presumed Gamma infections that were observed in 2021 were reinfections. If we also include cases of probable or possible reinfections, these percentages increase respectively to 22.7% (95% CI 14.3–34.2%) and 39.3% (95% CI 29.5–50.0%). Previous infection conferred a protection against reinfection of 85.3% (95% CI 71.3–92.7%), decreasing to respectively 72.5% (95% CI 54.7–83.6%) and 39.5% (95% CI 14.1–57.8%) if probable and possible reinfections are included.

Conclusions

Reinfection by Gamma is common and may play a significant role in epidemics where Gamma is prevalent, highlighting the continued threat variants of concern pose even to settings previously hit by substantial epidemics.

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  1. Version published to 10.1186/s12879-022-07094-y
  2. Version published to 10.1101/2021.05.10.21256644v2 on medRxiv
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    SciScore for 10.1101/2021.05.10.21256644: (What is this?)

    Please note, not all rigor criteria are appropriate for all manuscripts.

    Table 1: Rigor

    Ethicsnot detected.
    Sex as a biological variablenot detected.
    Randomizationnot detected.
    Blindingnot detected.
    Power Analysisnot detected.

    Table 2: Resources

    No key resources detected.

    Results from OddPub: We did not detect open data. We also did not detect open code. Researchers are encouraged to share open data when possible (see Nature blog).

    Results from LimitationRecognizer: An explicit section about the limitations of the techniques employed in this study was not found. We encourage authors to address study limitations.

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    • Thank you for including a protocol registration statement.

    Results from scite Reference Check: We found no unreliable references.

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  4. Version published to 10.1101/2021.05.10.21256644v1 on medRxiv