Objective To estimate the effectiveness of the inactivated whole virus vaccine, CoronaVac (Sinovac Biotech), against symptomatic covid-19 in the elderly population of São Paulo state, Brazil during widespread circulation of the gamma variant. Design Test negative case-control study. Setting Community testing for covid-19 in São Paulo state, Brazil. Participants 43 774 adults aged ≥70 years who were residents of São Paulo state and underwent reverse transcription polymerase chain reaction (RT-PCR) testing for SARS-CoV-2 from 17 January to 29 April 2021. 26 433 cases with symptomatic covid-19 and 17 622 test negative controls with covid-19 symptoms were formed into 13 283 matched sets, one case with to up to five controls, according to age, sex, self-reported race, municipality of residence, previous covid-19 status, and date of RT-PCR test (±3 days). Intervention Vaccination with a two dose regimen of CoronaVac. Main outcome measures RT-PCR confirmed symptomatic covid-19 and associated hospital admissions and deaths. Results Adjusted vaccine effectiveness against symptomatic covid-19 was 24.7% (95% confidence interval 14.7% to 33.4%) at 0-13 days and 46.8% (38.7% to 53.8%) at ≥14 days after the second dose. Adjusted vaccine effectiveness against hospital admissions was 55.5% (46.5% to 62.9%) and against deaths was 61.2% (48.9% to 70.5%) at ≥14 days after the second dose. Vaccine effectiveness ≥14 days after the second dose was highest for the youngest age group (70-74 years)—59.0% (43.7% to 70.2%) against symptomatic disease, 77.6% (62.5% to 86.7%) against hospital admissions, and 83.9% (59.2% to 93.7%) against deaths—and declined with increasing age. Conclusions Vaccination with CoronaVac was associated with a reduction in symptomatic covid-19, hospital admissions, and deaths in adults aged ≥70 years in a setting with extensive transmission of the gamma variant. Vaccine protection was, however, low until completion of the two dose regimen, and vaccine effectiveness was observe to decline with increasing age among this elderly population. Deidentified databases as well as the R codes will be deposited in the repository on publication of this article.

中文翻译：

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CoronaVac 疫苗在巴西伽马变异相关的 covid-19 流行期间对老年人的有效性：测试阴性病例对照研究

目的 评估在伽马变种广泛传播期间，灭活全病毒疫苗 CoronaVac（科兴生物科技）对巴西圣保罗州老年人群中出现症状的 covid-19 的有效性。设计测试阴性病例对照研究。在巴西圣保罗州开展针对 covid-19 的社区测试。参与者 43 774 名年龄 ≥ 70 岁的成年人，他们是圣保罗州居民，并于 2021 年 1 月 17 日至 4 月 29 日接受了 SARS-CoV-2 逆转录聚合酶链反应 (RT-PCR) 检测。 26 433 例有症状的 covid-19 病例17 622 名具有 covid-19 症状的测试阴性对照被分成 13 283 组匹配组，根据年龄、性别、自我报告的种族、居住城市、既往 covid-19 状态和RT-PCR 测试日期（±3 天）。采用两剂 CoronaVac 方案进行干预疫苗接种。主要结果指标 RT-PCR 证实了有症状的 covid-19 以及相关的入院和死亡。结果 调整后的疫苗针对有症状的 covid-19 的有效性在第二次接种后 0-13 天时为 24.7%（95% 置信区间为 14.7% 至 33.4%），在 ≥ 14 天时为 46.8%（38.7% 至 53.8%）。第二次接种后 14 天以上时，调整后的疫苗入院有效率为 55.5%（46.5% 至 62.9%），死亡有效率为 61.2%（48.9% 至 70.5%）。第二次接种后 14 天以上的疫苗有效性对于最年轻的年龄组（70-74 岁）而言最高——针对症状性疾病的疫苗有效性为 59.0%（43.7% 至 70.2%），针对入院的疫苗有效性为 77.6%（62.5% 至 86.7%），并且83.9%（59.2% 至 93.7%）的人不会死亡，并且随着年龄的增长而下降。结论 在γ变体广泛传播的环境中，接种 CoronaVac 疫苗可减少 70 岁以上成年人的 covid-19 症状、入院率和死亡率。然而，在完成两剂方案之前，疫苗的保护作用较低，并且观察到，在老年人群中，疫苗的有效性随着年龄的增长而下降。去识别化的数据库以及 R 代码将存放在存储库中关于本文的发表。