Effectiveness of a booster dose of COVID-19 vaccines during an outbreak of SARS-CoV-2 Omicron BA.2.2 in China: A case-control study.

Real-world evidence on the effectiveness of COVID-19 vaccines marketed in China against the Omicron BA.2.2 variant remains scarce. A case-control study was conducted to estimate the vaccine effectiveness (VE) of COVID-19 vaccines marketed in China (inactivated vaccines, an Ad5-nCoV vaccine, and a recombinant protein vaccine). There were 414 cases infected with SARS-CoV-2 and 828 close contacts whose test results were consecutively negative as controls during the outbreak of the Omicron variant in Lu'an City, Anhui Province, China, in April 2022. The overall adjusted VE against Omicron BA.2.2 variant infection in the vaccinated group with any COVID-19 vaccine was 35.0% (95% CI: -9.1-61.3%), whereas the adjusted VE for booster vaccination was 51.6% (95% CI: 15.2-72.4%). Subgroup analysis showed that the overall adjusted VE of the Ad5-nCoV vaccine (65.8%, 95% CI: 12.8-86.6%) during the outbreak while any dose of inactivated vaccines and recombinant protein vaccine offered no protection. The adjusted VE of three-dose inactivated vaccines was 48.0% (95% CI: 8.0-70.6%), and the two-dose Ad5-nCoV vaccine was 62.9% (95% CI: 1.8-86%). There is no protection from a three-dose recombinant protein vaccine. COVID-19 vaccines offered 46.8% (95% CI: 9.5-68.7%) protection from infection within six months. There were statistically significant differences between the VEs of heterologous booster (VE = 76.4%, 95% CI: 14.3-93.5%) and homologous booster vaccination (VE = 51.8%, 95% CI: 9.6-74.3%) (P = .036). Booster vaccination of COVID-19 vaccines offered more protection than full vaccination. A booster vaccination campaign for a booster dose after three doses of a recombinant protein vaccine must be urgently conducted.

The acceptance to heterologous booster vaccination of COVID-19 vaccine among HCWs and targeted population: A cross-sectional study in central China

Background There are few studies reported on the acceptance of heterologous booster vaccination for the COVID-19 vaccine among healthcare workers (HCWs) and the general population. We aimed to address that gap and explore determinant factors of acceptance of the heterologous booster vaccination. Methods We conducted a cross-sectional study to examine the prevalence and determinant factors of the acceptance of heterologous booster vaccination for the COVID-19 vaccine among HCWs and the targeted population. Results A total of 364 HCWs and 1,898 targeted populations were investigated in our study. 76.4% HCWs would recommend heterologous booster vaccination to their patients and 59.8% targeted population endorsed a clear willingness to receive this strategy. Compared with the adenoviral vector vaccine (AD5-nCOV), recombinant protein vaccine (ZF2001) was more preferred by HCWs (79.1%) and the targeted population (72.0%) as a heterologous booster vaccine. HCWs who did not work in the vaccination clinics were more likely to recommend heterologous booster vaccination (OR = 3.3, CI: 1.5–7.3). The targeted population aged 18–59 years (OR = 1.5, 95% CI:1.1–2.3), had a positive attitude toward COVID-19 vaccination (OR = 3.8, 95% CI: 1.7–8.6), had confidence in the safety of COVID-19 vaccines (OR = 6.6, 95% CI: 4.2–10.2), followed the recommendation of HCWs (OR = 33.6, 95% CI: 22.0–51.2), took initiative in collecting booster shots information (OR = 2.1, 95% CI: 1.5–3.0), and were familiar with the heterologous strategy (OR = 1.9, 95% CI: 1.1–3.1) were more likely to choose heterologous booster vaccination. The history of side effects of inactivated COVID-19 vaccine was a negative factor in choosing heterologous booster vaccination (OR = 0.4, 95% CI: 0.4–1.0). Conclusions The heterologous booster vaccination strategy on the COVID-19 vaccine could be widely accepted among HCWs, whereas its acceptance among targeted population was only moderate. Public authorities should make efforts to communicate the public about the effectiveness and safety of the heterologous booster vaccination which could help increase their willingness to get vaccinated.