# Protection of Prior SARS-CoV-2 Infection Against Different Variants, Including Omicron Descendants, in a Country with High Viral Transmission

## TL;DR

This study shows that prior infection with SARS-CoV-2 offers varying levels of protection against reinfection with different variants, including Omicron sublineages, in a country with high transmission.

## Contribution

The study quantifies protection against reinfection with multiple SARS-CoV-2 variants, including Omicron descendants, in a high-transmission setting.

## Key findings

- Prior infection provides 86.3% protection against Lambda variant reinfection.
- Protection against Omicron BA.1 is 34.9%, while protection against Omicron XBB is only 8.6%.
- Protection varies significantly among different Omicron sublineages.

## Abstract

Prior infection with SARS-CoV-2 has been reported to confer protection against reinfections. Because Peru has been affected by several variants of this virus, it is an ideal location to better explore this phenomenon. In this study, we aim to evaluate protection of prior SARS-CoV-2 infection against reinfection by variants during the COVID-19 pandemic in Peru.

A nested case-control study was carried out, using national data from Peru between 2021 and 2023. Five study periods were defined, delimited by the predominance of the main SARS-CoV-2 variants circulating during the pandemic. Cases were paired with controls in a 1 to 4 rate by sex, age, region, being a health worker, and the week of infection. Protection was calculated using conditional logistic regression to estimate odds ratios (OR) with 95% confidence intervals (95% CI) expressed as (1-OR) x100.

Protection from prior infection against SARS-CoV-2 reinfection was 86.3% (95% CI, 81.8 to 89.7) for Lambda, 73.0% (95% CI, 62.9 to 80.3) for Gamma, 84.7% (95% CI, 82.1 to 86.9) for Delta, 34.9% (95% CI, 25.5 to 43.1) for Omicron BA.1, 67.0% (95% CI, 58.7 to 73.6) for Omicron BA.2.12.1, 49.1% (95% CI, 40.5 to 56.5) for Omicron BA.4, 44.8% (95% CI, 39.9 to 49.3) for Omicron BA.5, 29.4% (95% CI, 18.2 to 39.1) for Omicron BQ, and 8.6% (95% CI, -0.5 to 16.9) for Omicron XBB.

Prior infection provides significant protection against SARS-CoV-2 reinfection episodes, although this varies widely among the different Omicron sublineages.