{"id":23668,"date":"2023-04-06T04:16:00","date_gmt":"2023-04-05T20:16:00","guid":{"rendered":"http:\/\/csccm.org.cn\/?p=23668"},"modified":"2023-04-09T00:09:55","modified_gmt":"2023-04-08T16:09:55","slug":"lancet-infect-dis%e5%8f%91%e8%a1%a8%e8%ae%ba%e6%96%87%ef%bc%9a%e5%b9%bf%e5%b7%9e%e8%a7%a3%e9%99%a4%e6%96%b0%e5%86%a0%e6%b8%85%e9%9b%b6%e6%94%bf%e7%ad%96%e5%90%8e%e7%9a%84%e6%84%9f%e6%9f%93%e7%8e%87","status":"publish","type":"post","link":"https:\/\/csccm.org.cn\/?p=23668","title":{"rendered":"[Lancet Infect Dis\u53d1\u8868\u8bba\u6587]\uff1a\u5e7f\u5dde\u89e3\u9664\u65b0\u51a0\u6e05\u96f6\u653f\u7b56\u540e\u7684\u611f\u67d3\u7387"},"content":{"rendered":"\n

CORRESPONDENCE|ONLINE FIRST<\/a><\/p>\n\n\n\n

Infection rate in Guangzhou after easing the zero-COVID policy: seroprevalence results to ORF8 antigen<\/h1>\n\n\n\n

Junyuan Huang, Shi Zhao, Ka Chun Chong, et al.<\/h3>\n\n\n\n

Lancet Infect Dis Published: February 17, 2023<\/h3>\n\n\n\n

DOI:https:\/\/doi.org\/10.1016\/S1473-3099(23)00112-3<\/a><\/h3>\n\n\n\n

On Dec 7, 2022, the Chinese government announced ten measures indicating the end of the zero-COVID policy, which was in effect for more than 2 years.1<\/a><\/sup>\u00a0Most of the stringent preventive measures, such as mandatory PCR testing, are no longer required. However, easing of restrictions has contributed to the emergence of new outbreaks predominantly by the SARS-CoV-2 omicron lineages BA5.2 and BF.7 in many cities, such as Beijing.2<\/a><\/sup>\u00a0With suspension of mass testing in mainland China after adjustment of the zero-COVID policy, empirical data on the epidemic growth and transmissibility of omicron variants are scarce. Until now, the number of infected cases and transmission rates were usually estimated using modelling with partial data.3<\/a><\/sup>\u00a0Previously, we reported that presence of the ORF8 antibody in blood is one of the most accurate serological markers of SARS-CoV-2 natural infection.4<\/a>,\u00a0<\/sup>\u00a05<\/a><\/sup>\u00a0Because the\u00a0ORF8<\/em>\u00a0gene is only expressed during SARS-CoV-2 replication, this serology test can confirm whether the patient has previously been infected with the virus and help to estimate the attack ratio.<\/p>\n\n\n\n

During Jan 5\u201314, 2023, we collected serum samples from 1500 patients aged 1\u201399 years at The First Affiliated Hospital of Guangzhou University of Chinese Medicine (Guangzhou, China), around 1 month after the zero-COVID policy was ended. Serum samples were tested using ELISA, with ORF8 protein used as the detection antigen (appendix p 1<\/a>). The demographic information of patients and ELISA results are shown in the\u00a0table<\/a>. The overall positive rate of ORF8 ELISA was 61\u00b75%. The samples were further stratified into five age groups with positive rates of 66\u00b72% in group 1\u201317 years, 71\u00b73% in group 18\u201339 years, 54\u00b71% in group 40\u201359 years, 55\u00b78% in group 60\u201379 years, and 64\u00b75% in group 80\u201399 years.<\/p>\n\n\n\n

After the zero-COVID policy ended, the age-specific infection attack ratio and disease transmission measures (ie, initial reproduction number and doubling time) were estimated by an age-specific renewal equation. We assumed an initial proportion of susceptibility was 98% on Dec 7, 2022, providing that stringent zero-COVID control measures were implemented in Guangzhou and that there had been no previous large scale COVID-19 outbreaks. The Markov chain Monte Carlo method was used to calculate the posterior estimates and corresponding credible intervals (CIs; appendix).<\/p>\n\n\n\n

We estimated that the overall infection attack ratio on the day of the exit strategy was 5\u00b77% (95% CI 4\u00b78\u20136\u00b78). With an estimated doubling time of 5\u00b73 days (95% CI 4\u00b78\u20135\u00b78), the overall infection attack ratio rapidly increased to 15\u00b72% (12\u00b73\u201318\u00b77) at 1 week and 32\u00b79% (26\u00b73\u201340\u00b72) at 2 weeks after the imposed day of the exit strategy. Among five age groups, individuals aged 1\u201317 and 18\u201339 years had higher infection attack ratio than those aged 40\u201399 years (table<\/a>;\u00a0appendix p 1<\/a>). By day 30 after the exit strategy, the infection attack ratios were 80\u00b77% (95% CI 72\u00b72\u201386\u00b78) for all age groups, 85\u00b71% (72\u00b70\u201392\u00b74) for age 1\u201317 years, 87\u00b75% (83\u00b73\u201390\u00b77) for age 18\u201339 years, 74\u00b73% (63\u00b77\u201382\u00b75) for age 40\u201359 years, 73\u00b79% (66\u00b77\u201379\u00b79) for age 60\u201379 years, and 75\u00b72% (60\u00b73\u201385\u00b76) for age 80\u201399 years.<\/p>\n\n\n\n

\"\"<\/a><\/figure>\n\n\n\n

Our research indicates that the COVID-19 epidemic spread fast in mainland China after the zero-COVID control measure was ended. Importantly, these results show that more than 80% of the studied population had already recovered from SARS-CoV-2 omicron infection. Herd immunity to the circulating omicron variants likely is high in Guangzhou and potentially in other urban areas in China with high transmission networks and this wave of transmission in China's urban areas is ceasing.<\/p>\n","protected":false},"excerpt":{"rendered":"

CORRESPONDENCE|ONLINE FIRST Infection rate in Guangzhou […]<\/p>\n","protected":false},"author":3,"featured_media":0,"comment_status":"closed","ping_status":"closed","sticky":false,"template":"","format":"standard","meta":[],"categories":[32,23],"tags":[],"_links":{"self":[{"href":"https:\/\/csccm.org.cn\/index.php?rest_route=\/wp\/v2\/posts\/23668"}],"collection":[{"href":"https:\/\/csccm.org.cn\/index.php?rest_route=\/wp\/v2\/posts"}],"about":[{"href":"https:\/\/csccm.org.cn\/index.php?rest_route=\/wp\/v2\/types\/post"}],"author":[{"embeddable":true,"href":"https:\/\/csccm.org.cn\/index.php?rest_route=\/wp\/v2\/users\/3"}],"replies":[{"embeddable":true,"href":"https:\/\/csccm.org.cn\/index.php?rest_route=%2Fwp%2Fv2%2Fcomments&post=23668"}],"version-history":[{"count":1,"href":"https:\/\/csccm.org.cn\/index.php?rest_route=\/wp\/v2\/posts\/23668\/revisions"}],"predecessor-version":[{"id":23670,"href":"https:\/\/csccm.org.cn\/index.php?rest_route=\/wp\/v2\/posts\/23668\/revisions\/23670"}],"wp:attachment":[{"href":"https:\/\/csccm.org.cn\/index.php?rest_route=%2Fwp%2Fv2%2Fmedia&parent=23668"}],"wp:term":[{"taxonomy":"category","embeddable":true,"href":"https:\/\/csccm.org.cn\/index.php?rest_route=%2Fwp%2Fv2%2Fcategories&post=23668"},{"taxonomy":"post_tag","embeddable":true,"href":"https:\/\/csccm.org.cn\/index.php?rest_route=%2Fwp%2Fv2%2Ftags&post=23668"}],"curies":[{"name":"wp","href":"https:\/\/api.w.org\/{rel}","templated":true}]}}