Duration of Severe Acute Respiratory Syndrome Coronavirus 2 Natural Immunity and Protection Against the Delta Variant: A Retrospective Cohort Study
03 December 2021
Excerpt:
Among 325 157 patients tested before 31 December 2020, 50 327 (15.5%) tested positive. After 1 July 2021 (Delta dominant period), 40 (0.08%) initially positive and 1494 (0.5%) initially negative patients tested positive. Protection of prior infection against reinfection with Delta was 85.4% (95% confidence interval [CI], 80.0–89.3).
________
Overall protection of previous infection was 85.7% (95% CI, 82.2–88.5) and lasted up to 13 months.