Abstract：
BACKGROUND: Hybrid SARS-CoV-2 immunity may provide longer duration protection against severe SARS-CoV-2 infection and hospitalisation than purely vaccine-derived immunity. Older adults represent a high-risk group for severe disease, yet available data is skewed towards younger adults.
METHODS: A prospective longitudinal study at a large London long-term care facility (LTCF) was conducted from March 2020 to April 2022 to assess the effect of hybrid versus vaccine-only immunity on SARS-CoV-2 infection in older adults during Omicron variant dominance. Hybrid immunity was assessed by a combination of SARS-CoV-2 polymerase chain reaction testing weekly (asymptomatic screening) and as required (symptomatic testing), as well as serial SARS-CoV-2 serology.
RESULTS: 280 participants (median age 82 yrs, IQR 76-88 yrs; 95.4% male) were followed up. 168/280 (60%) had evidence of hybrid immunity prior to the Omicron variant wave. Participants with hybrid immunity had substantially lower odds of acquiring COVID-19 infection during the Omicron wave compared to those with vaccine-only immunity (unadjusted odds ratio 0.26, 95% CI 0.14-0.47, chi-squared P < .0001). Participants with hybrid immunity had an odds ratio of 0.40 (0.19-0.79) for asymptomatic infection and 0.15 (0.06-0.34) for symptomatic infection (Likelihood ratio test, P < .0001).
CONCLUSIONS: Our data highlight potential opportunities to target ongoing booster vaccination campaigns for those most at risk of severe infection. Reporting of data in older adults will be of particular value to examine the effect of hybrid immunity as new variants continue to emerge and vaccination strategies evolve.
METHODS: A prospective longitudinal study at a large London long-term care facility (LTCF) was conducted from March 2020 to April 2022 to assess the effect of hybrid versus vaccine-only immunity on SARS-CoV-2 infection in older adults during Omicron variant dominance. Hybrid immunity was assessed by a combination of SARS-CoV-2 polymerase chain reaction testing weekly (asymptomatic screening) and as required (symptomatic testing), as well as serial SARS-CoV-2 serology.
RESULTS: 280 participants (median age 82 yrs, IQR 76-88 yrs; 95.4% male) were followed up. 168/280 (60%) had evidence of hybrid immunity prior to the Omicron variant wave. Participants with hybrid immunity had substantially lower odds of acquiring COVID-19 infection during the Omicron wave compared to those with vaccine-only immunity (unadjusted odds ratio 0.26, 95% CI 0.14-0.47, chi-squared P < .0001). Participants with hybrid immunity had an odds ratio of 0.40 (0.19-0.79) for asymptomatic infection and 0.15 (0.06-0.34) for symptomatic infection (Likelihood ratio test, P < .0001).
CONCLUSIONS: Our data highlight potential opportunities to target ongoing booster vaccination campaigns for those most at risk of severe infection. Reporting of data in older adults will be of particular value to examine the effect of hybrid immunity as new variants continue to emerge and vaccination strategies evolve.
摘要：
背景：杂种SARS-CoV-2免疫可能比单纯的疫苗来源的免疫提供针对严重SARS-CoV-2感染和住院的更长持续时间的保护。老年人是严重疾病的高危人群，然而，现有数据偏向年轻人。
方法：于2020年3月至2022年4月在伦敦一家大型长期护理机构（LTCF）进行了一项前瞻性纵向研究，以评估混合免疫与仅疫苗免疫对SARS-CoV-2感染的影响。通过每周SARS-CoV-2聚合酶链反应测试（无症状筛查）和必要时（症状测试）的组合来评估混合免疫，以及系列SARS-CoV-2血清学。
结果：280名参与者（平均年龄82岁，IQR76-88岁；男性占95.4%）随访。168/280（60％）在Omicron变异波之前有混合免疫的证据。与仅有疫苗免疫的参与者相比，具有混合免疫的参与者在Omicron波期间获得COVID-19感染的几率大大降低(未调整的优势比0.26，95%CI0.14-0.47，卡方P<.0001)。混合免疫的参与者无症状感染的比值比为0.40（0.19-0.79），有症状感染的比值比为0.15（0.06-0.34）（似然比测试，P<.0001)。
结论：我们的数据强调了针对严重感染风险最高的人群正在进行的加强疫苗接种活动的潜在机会。随着新的变异不断出现和疫苗接种策略的发展，报告老年人的数据对于检查混合免疫的影响将具有特别的价值。
方法：于2020年3月至2022年4月在伦敦一家大型长期护理机构（LTCF）进行了一项前瞻性纵向研究，以评估混合免疫与仅疫苗免疫对SARS-CoV-2感染的影响。通过每周SARS-CoV-2聚合酶链反应测试（无症状筛查）和必要时（症状测试）的组合来评估混合免疫，以及系列SARS-CoV-2血清学。
结果：280名参与者（平均年龄82岁，IQR76-88岁；男性占95.4%）随访。168/280（60％）在Omicron变异波之前有混合免疫的证据。与仅有疫苗免疫的参与者相比，具有混合免疫的参与者在Omicron波期间获得COVID-19感染的几率大大降低(未调整的优势比0.26，95%CI0.14-0.47，卡方P<.0001)。混合免疫的参与者无症状感染的比值比为0.40（0.19-0.79），有症状感染的比值比为0.15（0.06-0.34）（似然比测试，P<.0001)。
结论：我们的数据强调了针对严重感染风险最高的人群正在进行的加强疫苗接种活动的潜在机会。随着新的变异不断出现和疫苗接种策略的发展，报告老年人的数据对于检查混合免疫的影响将具有特别的价值。
