Vaccine effectiveness against hospital admission in South African health care workers who received a homologous booster of Ad26.COV2 during an Omicron COVID19 wave: Preliminary Results of the Sisonke 2 Study. (preprint)

Following the results of the ENSEMBLE 2 study, which demonstrated improved vaccine efficacy of a two-dose regimen of Ad26.COV.2 vaccine given 2 months apart, we expanded the Sisonke study which had provided single dose Ad26.COV.2 vaccine to almost 500 000 health care workers (HCW) in South Africa to include a booster dose of the Ad26.COV.2. Sisonke 2 enrolled 227 310 HCW from the 8 November to the 17 December 2021. Enrolment commenced before the onset of the Omicron driven fourth wave in South Africa affording us an opportunity to evaluate early VE in preventing hospital admissions of a homologous boost of the Ad26.COV.2 vaccine given 6-9 months after the initial vaccination in HCW. We estimated vaccine effectiveness (VE) of the Ad26.COV2.S vaccine booster in 69 092 HCW as compared to unvaccinated individuals enrolled in the same managed care organization using a test negative design. We compared VE against COVID19 admission for omicron during the period 15 November to 20 December 2021. After adjusting for confounders, we observed that VE for hospitalisation increased over time since booster dose, from 63% (95%CI 31-81%); to 84% (95% CI 67-92%) and then 85% (95% CI: 54-95%), 0-13 days, 14-27 days, and 1-2 months post-boost. We provide the first evidence of the effectiveness of a homologous Ad26.COV.2 vaccine boost given 6-9 months after the initial single vaccination series during a period of omicron variant circulation. This data is important given the increased reliance on the Ad26.COV.2 vaccine in Africa.

EPIDEMIOLOGICAL AND CLINICAL CHARACTERISTICS OF COVID-19 PATIENTS IN KENYA (preprint)

Abstract Background More than 49,000 cases of infection and 900 deaths from COVID-19 have been recorded in the Kenya. However, the characteristics and risk factors for severe outcomes among hospitalized COVID-19 patients in this setting have not been described. Methods We extracted demographic, laboratory, clinical and outcome data from medical records of RT-PCR confirmed SARS-CoV2 patients admitted in six hospitals in Kenya between March and September, 2020. We used Cox proportional hazards regressions to determine factors related to in-hospital mortality. Results Data from 787 COVID-19 patients was available. The median age was 43 years (IQR 30-53), with 505 (64%) males. At admission, 455 (58%) were symptomatic. The commonest symptoms were cough (337, 43%), loss of taste or smell (279, 35%), and fever (126, 16%). Co-morbidities were reported in 340 (43%), with cardiovascular disease, diabetes and HIV documented in 130 (17%), 116 (15%), 53 (7%) respectively. 90 (11%) were admitted to ICU for a mean of 11 days, 52 (7%) were ventilated with a mean of 10 days, 107 (14%) died. The risk of death increased with age [hazard ratio (HR) 1.57 (95% CI 1.13-2.19)] for persons >60 years compared to those <60 years old; having co-morbidities [HR 2.34 (1.68-3.25)]; and among males [HR 1.76 (1.27, 2.44)] compared to females. Elevated white blood cell count and aspartate aminotransferase were associated with higher risk of death. Conclusions We identify the risk factors for mortality that may guide stratification of high risk patients.