Vaccination effects on post-infection outcomes in the Omicron BA.2 outbreak in Shanghai

Abstract

Omicron and its sublineages are currently predominant and have triggered epidemiological waves of SARS-CoV-2 around the world due to their high transmissibility and strong immune escape ability. Vaccines are key measures to control the COVID-19 burden. Omicron BA.2 caused a large-scale outbreak in Shanghai since March 2022 and resulted in over 0.6 million laboratory-confirmed infections. The vaccine coverage of primary immunization among residents aged 3 years and older in Shanghai exceeded 90%, and inactivated COVID-19 vaccines were mainly delivered. In the context of high vaccine coverage, we conducted a cohort study to assess vaccine effects on reducing the probability of developing symptoms or severity of disease in infections or nonsevere cases. A total of 48,243 eligible participants were included in this study, the majority of whom had asymptomatic infections (31.0%) and mild-to-moderate illness (67.9%). Domestically developed COVID-19 vaccines provide limited protection to prevent asymptomatic infection from developing into mild-to-moderate illness and durable protection to prevent nonsevere illness from progressing to severe illness caused by Omicron BA.2. Partial vaccination fails to provide effective protection in any situation. The level of vaccine effects on disease progression in the elderly over 80 years old was relatively lower compared with other age groups. Our study results added robust evidence for the vaccine performance against Omicron infection and could improve vaccine confidence.

Clinical characteristics and immunogenicity after Omicron breakthrough infection in patients with chronic hepatitis B infection: A longitudinal observational study

“…Even though our previous cohort study showed that booster dose of vaccination can elicit robust antibody responses against the WT strain, 16 all patients with CHB with ongoing follow‐up in this cohort were infected with COVID‐19 during the first wave of Omicron. This is similar to that reported in previous studies on the general population, 24,25 and further confirms the weak protection of WT vaccine against Omicron infection. After BTI, the clinical symptoms of COVID‐19 were mild to moderate, which was similar to previous observations 13,25,26 .…”

Neutralization of SARS-CoV-2 BQ.1.1 and XBB.1.5 by Breakthrough Infection Sera from Previous and Current Waves in China

“…China successfully contained multiple COVID-19 outbreaks by adhering to a strict “zero-Covid” policy. However, due to the high transmissibility and immune escape properties, Omicron BA.2 caused a local outbreak in Shanghai since March 2022 and resulted in over 0.6 million laboratory-confirmed infections(Chen et al ., 2022; Wu et al ., 2023). Since the “zero-Covid” policy was lifted in December 2022, China has experienced a surge in COVID-19 infections nationwide.…”

The effectiveness of COVID–19 vaccination against all–cause mortality in patients with type 2 diabetes mellitus: The observation during the initial period of the cancellation of the “Dynamic Zero Policy” in mainland China

“…The surveillance data showed positive nucleic acid test rate in the general population sharply increased to a peak of 29.2% on Dec 25, 2022, and gradually fell to 1.5% on Feb 6, 2023 [6] . Two or three doses of inactivated COVID–19 vaccines which was vaccinated in most Chinese population, could provide strong and durable protection against severe disease and death, according to the data in omicron pandemic from HongKong [9] and ShangHai [10] . However, the above assessment was conducted prior to the cancellation of the “Dynamic Zero Policy” strategy.…”