Previous SARS-CoV-2 infections and their impact on the protection from reinfection during the Omicron BA.5 wave – a nested case-control study among vaccinated adults in Sweden

IF 1.5 Q4 INFECTIOUS DISEASES

IJID regions Pub Date : 2024-03-01 DOI:10.1016/j.ijregi.2024.02.004

Fredrik Kahn , Carl Bonander , Mahnaz Moghaddassi , Claus Bohn Christiansen , Louise Bennet , Ulf Malmqvist , Malin Inghammar , Jonas Björk

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Abstract

Objectives

We evaluated the protection afforded by SARS-CoV-2 infection-induced immunity against reinfection among working-age vaccinated individuals during a calendar period from June to December 2022 when Omicron BA.5 was the dominating subvariant in Scania County, Sweden.

Methods

The study cohort (n = 71,592) mainly consisted of health care workers. We analyzed 4144 infected cases during the Omicron BA.5 dominance and 41,440 sex- and age-matched controls with conditional logistic regression.

Results

The average protection against reinfection was marginal (16%, 95% confidence interval [CI] 7-23%) during the study period but substantially higher for recent infections. Recent infection (3-6 months) with Omicron BA.2 and BA.5 offered strong protection (86%, 95% CI 68-94% and 78%, 95% CI 69-84%), whereas more distant infection (6-12 months) with Omicron BA.1, BA.2, and the variants before Omicron offered marginal or no protection.

Conclusions

These findings suggest that infection-induced immunity contributes to short-term population protection against infection with the subvariant BA.5 among working-age vaccinated individuals but wanes considerably with time, independent of the virus variant.

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在 Omicron BA.5 疫潮期间曾感染过 SARS-CoV-2 及其对再感染保护的影响--对瑞典已接种疫苗的成年人进行的巢式病例对照研究

目的我们评估了 2022 年 6 月至 12 月 Omicron BA.5 亚变异体在瑞典斯堪尼亚县占主导地位期间，SARS-CoV-2 感染引起的免疫对工作年龄接种者再感染的保护作用。我们通过条件逻辑回归分析了在 Omicron BA.5 占主导地位期间的 4144 例感染病例和 41440 例性别和年龄匹配的对照病例。近期（3-6 个月）感染 Omicron BA.2 和 BA.5 可提供较强的保护（86%，95% CI 68-94% 和 78%，95% CI 69-84%），而较远期（6-12 个月）感染 Omicron BA.1、BA.2 和 Omicron 之前的变种可提供微弱保护或无保护。

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