In this multi-center prospective test-negative case-control study in Japan, the effectiveness of both BA.1-containing and BA.4/BA.5-containing bivalent COVID-19 mRNA vaccines against symptomatic infection during the BA.5-dominant period was high compared to no vaccination (65% and 76%) and moderate compared to monovalent vaccines administered over half a year before (46% combined).

Since the first confirmed human infection with avian influenza A(H5N1) virus was reported in Hong Kong Special Administrative Region in 1997, sporadic zoonotic avian influenza viruses causing illness in humans have been identified globally, with the WHO Western Pacific Region as one of the hotspots. From November 2003, when a resurgence of H5N1 virus activity in humans and animals occurred, through September 2017, 1,838 human infections with avian influenza viruses in the region were reported to WHO. Viruses infecting humans were A(H5N1), A(H5N6), A(H6N1), A(H7N9), A(H9N2) and A(H10N8). The vast majority of infections were with H7N9 (n=1,562) and H5N1 (n=238) viruses, and most (n=1583, 86%) were reported from December through April. In poultry and wild birds, H5N1 and H5N6 subtypes were the most widely distributed, with outbreaks reported from ten and eight countries and areas, respectively. Regional analyses of human infections with avian influenza subtypes revealed distinct patterns and variations in epidemiology across countries, age, and time. Such epidemiologic patterns may not be apparent from aggregated global summaries or isolated country reports; regional assessment can offer additional insight that can inform risk assessment and response efforts. As infected animals and contaminated environments are the primary source of human infections, regional analyses that bring together surveillance data from human and animal health sectors are an important basis for exposure and transmission risk assessment and public health action. A One Health approach combining sustained event-based surveillance with enhanced collaboration between the human, animal (domestic and wildlife), and environmental sectors will provide a basis to inform joint risk assessment and coordinated response capacities

Objective: Monitoring the prevalence of severe acute respiratory syndrome coronavirus 2 (SARS-CoV-2) variants is important due to concerns regarding infectivity, transmissibility, immune evasion and disease severity. We evaluated the temporal and regional replacement of previous SARS-CoV-2 variants by the emergent strains, Alpha and Delta. Methods: We obtained the results of polymerase chain reaction screening tests for variants conducted in multiple commercial laboratories. Assuming that all previous strains would be replaced by one variant, the new variant detection rate was estimated by fitting a logistic growth model. We estimated the transmission advantage of each new variant over the pre-existing virus strains. Results: The variant with the N501Y mutation was first identified in the Kinki region in early February 2021, and by early May, it had replaced more than 90% of the previous strains. The variant with the L452R mutation was first detected in the Kanto-Koshin region in mid-May, and by early August, it comprised more than 90% of the circulating strains. Compared with pre-existing strains, the variant with the N501Y mutation showed transmission advantages of 48.2% and 40.3% in the Kanto-Koshin and Kinki regions, respectively, while the variant with the L452R mutation showed transmission advantages of 60.1% and 71.9%, respectively. Discussion: In Japan, Alpha and Delta variants displayed regional differences in the replacement timing and their relative transmission advantages. Our method is efficient in monitoring and estimating changes in the proportion of variant strains in a timely manner in each region.