Abstract：
BACKGROUND: Data on protection afforded by updated COVID-19 vaccines (bivalent/XBB 1.5 monovalent) against the emergent JN.1 variant remains limited.
METHODS: We conducted a retrospective population-based cohort study amongst all boosted Singaporeans aged ≥18 years during a COVID-19 wave predominantly driven by JN.1, from 26th November 2023 to 13th January 2024. Multivariable Cox regression was utilised to assess risk of SARS-CoV-2 infection and COVID-19 associated emergency-department (ED) visits/hospitalizations, stratified by vaccination status/prior infection; with individuals last boosted ≥1 year utilized as the reference category. Vaccination and infection status were classified using national registries.
RESULTS: 3,086,562 boosted adult Singaporeans were included in the study population, accounting for 146,863,476 person-days of observation. During the JN.1 outbreak, 28,160 SARS-CoV-2 infections were recorded, with 2,926 hospitalizations and 3,747 ED-visits. Compared with individuals last boosted ≥1 year prior with ancestral monovalent vaccines, receipt of an updated XBB.1.5 booster 8-120 days prior was associated with lower risk of JN.1 infection (adjusted-hazard-ratio, aHR = 0.59[0.52-0.66]), COVID-19 associated ED-visits (aHR = 0.50[0.34-0.73]) and hospitalizations(aHR = 0.58[0.37-0.91]), while receipt of a bivalent booster 121-365 days prior was associated with lower risk of JN.1 infection (aHR = 0.92[0.88-0.95]) and ED-visits (aHR = 0.80[0.70-0.90]). Lower risk of COVID-19 hospitalization during the JN.1 outbreak (aHR = 0.57[0.33-0.97]) was still observed following receipt of an updated XBB.1.5 booster 8-120 days prior, even when analysis was restricted to previously infected individuals.
CONCLUSIONS: Recent receipt of updated boosters conferred protection against SARS-CoV-2 infection and ED-visits/hospitalization during a JN.1 variant wave, in both previously infected and uninfected individuals. Annual booster doses confer protection during COVID-19 endemicity.
METHODS: We conducted a retrospective population-based cohort study amongst all boosted Singaporeans aged ≥18 years during a COVID-19 wave predominantly driven by JN.1, from 26th November 2023 to 13th January 2024. Multivariable Cox regression was utilised to assess risk of SARS-CoV-2 infection and COVID-19 associated emergency-department (ED) visits/hospitalizations, stratified by vaccination status/prior infection; with individuals last boosted ≥1 year utilized as the reference category. Vaccination and infection status were classified using national registries.
RESULTS: 3,086,562 boosted adult Singaporeans were included in the study population, accounting for 146,863,476 person-days of observation. During the JN.1 outbreak, 28,160 SARS-CoV-2 infections were recorded, with 2,926 hospitalizations and 3,747 ED-visits. Compared with individuals last boosted ≥1 year prior with ancestral monovalent vaccines, receipt of an updated XBB.1.5 booster 8-120 days prior was associated with lower risk of JN.1 infection (adjusted-hazard-ratio, aHR = 0.59[0.52-0.66]), COVID-19 associated ED-visits (aHR = 0.50[0.34-0.73]) and hospitalizations(aHR = 0.58[0.37-0.91]), while receipt of a bivalent booster 121-365 days prior was associated with lower risk of JN.1 infection (aHR = 0.92[0.88-0.95]) and ED-visits (aHR = 0.80[0.70-0.90]). Lower risk of COVID-19 hospitalization during the JN.1 outbreak (aHR = 0.57[0.33-0.97]) was still observed following receipt of an updated XBB.1.5 booster 8-120 days prior, even when analysis was restricted to previously infected individuals.
CONCLUSIONS: Recent receipt of updated boosters conferred protection against SARS-CoV-2 infection and ED-visits/hospitalization during a JN.1 variant wave, in both previously infected and uninfected individuals. Annual booster doses confer protection during COVID-19 endemicity.
摘要：
背景：更新的COVID-19疫苗（二价/XBB1.5单价）提供的针对紧急JN.1变体的保护数据仍然有限。
方法：我们在2023年11月26日至2024年1月13日主要由JN.1驱动的COVID-19波中，对所有≥18岁的新加坡人进行了一项基于人群的回顾性队列研究。多变量Cox回归用于评估SARS-CoV-2感染和COVID-19相关急诊（ED）就诊/住院的风险，按疫苗接种状态/既往感染进行分层;将最后一次强化≥1年的个体用作参考类别。使用国家登记处对疫苗接种和感染状况进行分类。
结果：3,086,562名成年新加坡人被纳入研究人群，占观察天数146863,476人。在JN.1爆发期间，记录了28,160例SARS-CoV-2感染，2,926例住院和3,747例急诊就诊。与使用祖先单价疫苗前最后一次加强≥1年的个体相比，在8-120天之前接受更新的XBB.1.5加强剂与JN.1感染的风险较低相关(调整后的危险比，aHR=0.59[0.52-0.66])，COVID-19相关的ED访视（aHR=0.50[0.34-0.73]）和住院（aHR=0.58[0.37-0.91]），而在121-365天之前接受二价加强剂与JN.1感染(aHR=0.92[0.88-0.95])和ED访视(aHR=0.80[0.70-0.90])的风险较低相关。在JN.1爆发期间，在8-120天前收到更新的XBB.1.5加强剂后，仍观察到COVID-19住院风险较低（aHR=0.57[0.33-0.97]），即使分析仅限于以前感染的个体。
结论：最近收到的最新助推器在JN.1变异波中保护了SARS-CoV-2感染和ED就诊/住院，在以前感染和未感染的个体中。在COVID-19流行期间，年度加强剂量可提供保护。
方法：我们在2023年11月26日至2024年1月13日主要由JN.1驱动的COVID-19波中，对所有≥18岁的新加坡人进行了一项基于人群的回顾性队列研究。多变量Cox回归用于评估SARS-CoV-2感染和COVID-19相关急诊（ED）就诊/住院的风险，按疫苗接种状态/既往感染进行分层;将最后一次强化≥1年的个体用作参考类别。使用国家登记处对疫苗接种和感染状况进行分类。
结果：3,086,562名成年新加坡人被纳入研究人群，占观察天数146863,476人。在JN.1爆发期间，记录了28,160例SARS-CoV-2感染，2,926例住院和3,747例急诊就诊。与使用祖先单价疫苗前最后一次加强≥1年的个体相比，在8-120天之前接受更新的XBB.1.5加强剂与JN.1感染的风险较低相关(调整后的危险比，aHR=0.59[0.52-0.66])，COVID-19相关的ED访视（aHR=0.50[0.34-0.73]）和住院（aHR=0.58[0.37-0.91]），而在121-365天之前接受二价加强剂与JN.1感染(aHR=0.92[0.88-0.95])和ED访视(aHR=0.80[0.70-0.90])的风险较低相关。在JN.1爆发期间，在8-120天前收到更新的XBB.1.5加强剂后，仍观察到COVID-19住院风险较低（aHR=0.57[0.33-0.97]），即使分析仅限于以前感染的个体。
结论：最近收到的最新助推器在JN.1变异波中保护了SARS-CoV-2感染和ED就诊/住院，在以前感染和未感染的个体中。在COVID-19流行期间，年度加强剂量可提供保护。
