A Large-Scale Online Survey on Clinical Severity and Associated Risk Factors for SARS-CoV-2 Omicron Infection — China, April–May 2023

   A comprehensive online survey conducted in China between May 23 and May 30, 2023, reveals critical insights into the clinical symptoms and severity of COVID-19 infections, particularly focusing on the recent surge in cases caused by the Omicron variant. Encompassing 42,987 participants across 31 provincial-level administrative divisions (PLADs), the study differentiates between initial infections and re-infections, providing a nuanced understanding of the pandemic's current state. Notably, initial infections presented a higher prevalence of general, neurological, and gastrointestinal symptoms, while re-infections were characterized mainly by upper respiratory symptoms. The study's findings indicate a significant decrease in severe outcomes like high fever, hospitalization, ICU admission, and pneumonia in re-infected individuals. Interestingly, re-infections also showed a negative correlation with the number of symptoms and viral shedding duration. Age and pre-existing diseases emerged as primary risk factors for increased severity, while vaccination was identified as a protective factor. The study emphasizes the importance of proactive healthcare for older and middle-aged individuals, as well as those with underlying conditions, due to their heightened vulnerability. These findings offer crucial guidance for clinical diagnosis, treatment, and future epidemic prevention strategies, highlighting the ongoing relevance of vaccination and the need for comprehensive healthcare approaches in managing COVID-19.

   For more information: https://weekly.chinacdc.cn/en/article/doi/10.46234/ccdcw2024.059

Investigation of Nasal Mucosal IgA Responses in the Population Following COVID-19 Pandemic — China, September 2022–August 2023

   Understanding the relationship between mucosal immunoglobulin A (IgA) and SARS-CoV-2 infection is pivotal to guiding preventative measures and policies. A new study analyzed IgA antibody responses in 3,421 COVID-19 survivors from Hubei Province post the 2022 Omicron surge to investigate IgA’s role in long-term immunity. Using colloidal gold-based rapid tests and comprehensive surveys, researchers identified the persistence of IgA antibodies beyond six months in a significant subset of participants, regardless of symptom severity, vaccination status, or frequency of infection. For those with a history of severe symptoms, elevated IgA levels suggest a stronger immune response. Intriguingly, the study notes that individuals can experience asymptomatic reinfections while maintaining IgA production. The prevalence of higher IgA levels observed in this cohort may allude to a lowered susceptibility to SARS-CoV-2 upon future exposure. This research underscores the complexity of immune responses and reinforces the importance of mucosal IgA in respiratory virus defense. These insights can play a critical role in gauging herd immunity and shaping disease prevention strategies, particularly in the wake of new SARS-CoV-2 variants.

   For more information: https://weekly.chinacdc.cn/en/article/doi/10.46234/ccdcw2024.060

Predictors of Global Disparities in COVID-19 Vaccination Coverage — 219 Countries and Territories, December 2020–July 2022

   Our research investigated the factors influencing disparities in COVID-19 vaccination rates across 219 countries and territories as of July 2022. Data analysis revealed significant associations between vaccination coverage and various country-level indicators, such as demographics, socio development status, pandemic preparedness, governance, trust, and COVAX participation. Notably, a lower proportion of young population (aged 0–14) and improved pandemic preparedness linked to increased vaccination rates. Trust in government emerged as a key factor in COVID-19 vaccination, underscoring its importance in managing public response to health crises. Surprisingly, despite high vaccine delivery or acceptance rates in some countries, vaccination coverage remained low, suggesting a disconnect between vaccine availability and public willingness or ability to receive it. Our findings emphasize the need for enhanced pandemic preparedness and governance, coupled with building trust in government and healthcare systems. These factors are crucial for effective pandemic response and ensuring equitable vaccine distribution globally. The study's limitations, including potential ecological fallacies and multicollinearity, warrant cautious interpretation but offer valuable insights for future pandemic management and vaccine distribution strategies.

   For more information: https://weekly.chinacdc.cn/en/article/doi/10.46234/ccdcw2024.062

Genomic Surveillance for SARS-CoV-2 Variants: Dominance of XBB Replacement — China, January–June 2023

   A comprehensive study conducted in the first half of 2023 has illuminated the evolving landscape of SARS-CoV-2 variants in China, marking a notable shift towards the dominance of the XBB variant starting from April. This variant, a recombinant of Omicron subvariants, has shown an enhanced ability to evade immunity, consequently leading to its rapid dissemination globally. The study utilized data from 56,486 domestic and 8,669 imported COVID-19 cases, revealing a nuanced transition period during which the XBB variants gradually supplanted previous strains such as BA.5.2 and BF.7,with variation in timing across different PLADs. Notably, the study found that the prevalence of XBB in imported cases significantly influenced its spread in local populations, suggesting a link between imported cases and local transmission dynamics. Additionally, the replacement of the BF.7 variants by XBB occurred more slowly than that of BA.5.2, potentially due to antigenic similarities between XBB and BF.7, underscoring the complex interplay of viral mutations in variant dominance. These findings underscore the importance of robust surveillance systems in monitoring variant shifts and preparing for future dominant strains, highlighting the role of imported cases in shaping local epidemic patterns. This study contributes to our understanding of the dynamics of SARS-CoV-2 variant replacement in China, providing insights into the factors influencing the spread and dominance of new variants.

   For more information: https://weekly.chinacdc.cn/en/article/doi/10.46234/ccdcw2024.061

Early Detection of the Emerging SARS-CoV-2 BA.2.86 Lineage Through Wastewater Surveillance Using a Mediator Probe PCR Assay — Shenzhen City, Guangdong Province, China, 2023

   Researchers have established a wastewater surveillance system that allowed the early detection of the SARS-CoV-2 BA.2.86 lineage in the city of Shenzhen, China, as reported in a recent study. In response to the World Health Organization's classification of BA.2.86 as a variant under surveillance, the city’s 38 wastewater treatment plants and 9 pump stations were monitored using a novel mediator probe PCR assay. This method specifically targeted the variant’s distinct spike protein mutation and provided a cost-effective, unbiased means for tracking SARS-CoV-2 variants without clinical patient samples. Despite limited clinical diagnoses post-pandemic, which hinder prompt surveillance, the wastewater-based approach revealed the emergence of the BA.2.86 lineage across six districts before any local clinical cases were reported. This underscores the variant’s undisclosed prevalence and the strategic need for increased monitoring in port areas. The study's results demonstrate the importance and effectiveness of wastewater surveillance in early variant detection and in bolstering public health readiness.

   For more information: https://weekly.chinacdc.cn/en/article/doi/10.46234/ccdcw2024.063