What question did this study set out to answer?

To determine the duration of natural immunity following SARS-CoV-2 infection and assess its protective effectiveness against reinfection with the Delta variant.

December 1, 2021Clinical Infectious DiseasesOpen Access

Duration of Severe Acute Respiratory Syndrome Coronavirus 2 Natural Immunity and Protection Against the Delta Variant: A Retrospective Cohort Study

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Authors

PKPriscilla KimBiola University SGSteven M. GordonFlorida State University MSMegan SheehanUniversity of Pennsylvania

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Implication

Retrospective cohort study demonstrates robust protection against Delta reinfection after prior SARS-CoV-2 infection, indicating natural immunity persists for at least 13 months.

Key Points

To determine the duration of natural immunity following SARS-CoV-2 infection and assess its protective effectiveness against reinfection with the Delta variant.
Retrospective cohort study evaluating patients tested for SARS-CoV-2 by PCR across two cohorts: a Delta variant cohort (N=325,157 tested between March 9 and December 31, 2020) and a long-term effectiveness cohort (N=152,656 tested between March 9 and August 30, 2020) with follow-up through September 9, 2021.
Primary outcome was reinfection, defined as a positive PCR test occurring >90 days after an initial positive test.
During the Delta-dominant period starting July 1, 2021, reinfection occurred in 40 of 50,327 initially positive patients (0.08%) compared to 1,494 of 274,830 initially negative patients (0.5%), yielding 85.4% protection against Delta reinfection (95% CI, 80.0–89.3).
In the long-term cohort, reinfection after ≥90 days occurred in 81 of 11,186 initially positive patients (0.7%) versus 7,167 of 141,470 initially negative patients (5.1%), demonstrating 85.7% overall protection (95% CI, 82.2–88.5) lasting up to 13 months, with slightly lower protection in patients aged >65 years.

Cite This Study

Kim et al. (2021) studied this question.

synapsesocial.com/papers/6a85ac368e43bc0304d0ca93 https://doi.org/10.1093/cid/ciab999

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Implication

Retrospective cohort study demonstrates robust protection against Delta reinfection after prior SARS-CoV-2 infection, indicating natural immunity persists for at least 13 months.

Duration of Severe Acute Respiratory Syndrome Coronavirus 2 Natural Immunity and Protection Against the Delta Variant: A Retrospective Cohort Study

Discussion

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Implication

Key Points

Cite This Study

Duration of Severe Acute Respiratory Syndrome Coronavirus 2 Natural Immunity and Protection Against the Delta Variant: A Retrospective Cohort Study

Discussion

Member takes

Implication

Key Points

Cite This Study

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