Effectiveness of inactive COVID-19 vaccines against severe illness in B.1.617.2 (Delta) variant-infected patients in Jiangsu, China

Abstract

The SARS-CoV-2 B.1.617.2 (Delta) variant has caused a new surge in the number of COVID-19 cases. The effectiveness of vaccines against this variant is not fully understood. Using data from a recent large-scale outbreak of COVID-19 in China, we conducted a real-world study to explore the effect of inactivated vaccine immunization on the course of disease in patients infected with Delta variants. We recruited 476 confirmed cases over the age of 18, of which 42 were severe. After adjusting for age, gender, and comorbidities, patients who received two doses of inactivated vaccine (fully vaccinated) had an 88% reduced risk in progressing to the severe stage (adjusted OR: 0.12, 95% CI: 0.02- 0.45). However, this protective effect was not observed in patients who only received only one dose of the vaccine(adjusted OR: 1.11, 95% CI: 0.51- 2.36). The full immunization offered 100% protection from a severe illness among women. The effect of the vaccine was potentially affected by underlying medical conditions (OR: 0.26, 95% CI: 0.03-1.23). This is the largest real-world study confirming the effectiveness of inactive COVID-19 vaccines against severe illness in Delta variant-infected patients in Jiangsu, China.

Projecting the transition of COVID-19 burden towards the young population while vaccines are rolled out: a modelling study

“…b Pooling the effectiveness of inactivated COVID-19 vaccines against severe illness caused by the Delta variant estimated in the recent outbreaks of the Delta variant in Guangdong [22,23] and Jiangsu [24], China, we assume conservative effectiveness in preventing serious illness.…”

“…The vaccines used in mainland China were developed using historical SARS-CoV-2 lineages and have proven to be highly effective in protecting against severe illness caused by the Delta variant [22][23][24]. However, their effectiveness in preventing infection appears to be reduced [25].…”

“…A higher increase is observed in the rate ratios of hospitalisation for these two population groups: 178% and 191% for children aged 0-2 and 3-11 years, respectively. At the same time, the rate ratios in adults aged 1) [22][23][24]. Should the VE against the infection of the Delta variant be increased to >84% from 54.3% used in the baseline [35], the "adults+adolescents+children" vaccination strategy is estimated to reduce the number of deaths by 99% even in the absence of any NPIs, leading to <40,000 deaths over 1 year, similar to the annual excess respiratory disease deaths associated with influenza in China [50] (Fig S7 ).…”

“…In our model, VE in preventing ICU admissions and deaths caused by a Delta variant infection was set at 93%, based on real-world VE studies in Guangdong and Jiangsu, China (Table 1) [22][23][24]. Should the VE against the infection of the Delta variant be increased to >84% from 54.3% used in the baseline [35], the "adults+adolescents+children" vaccination strategy is estimated to reduce the number of deaths by 99% even in the absence of any NPIs, leading to <40,000 deaths over 1 year, similar to the annual excess respiratory disease deaths associated with influenza in China [50] (Fig S7 ).…”

Investigating vaccine-induced immunity and its effect in mitigating SARS-CoV-2 epidemics in China

“…The relative VE against infection within 0–13 days after second dose comparted with maximum protection is 83.8% for Delta variant [ 44 ]. VE against death for individuals aged 18–59 years old is 93% for Delta variant [ 45 – 47 ]. We explored higher VE values against infection [ 48 ] and tested a two-dose schedule with a 14-day interval as sensitivity analyses (Additional file 1 : Tab.…”