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BACKGROUNDHepatitis B virus (HBV) infection is one of the major concerns for the safety of blood transfusion in high‐prevalent countries such as in China. Prior studies outside of China have shown hepatitis B surface antigen (HBsAg) false‐reactive rate of 0.02% to 0.04%. Similarly, false‐negative HBsAg and HBV DNA results may occur in infected donors. Our study analyzed HBsAg enzyme‐linked immunosorbent assay (ELISA)‐reactive but NAT‐negative donations in Shenzhen Blood Center, China.STUDY DESIGN AND METHODSHBsAg ELISA‐positive/NAT‐negative plasma samples identified from screening 101,025 donations during 2017‐2018 were analyzed by molecular and serologic tests including neutralization, chemiluminescence immunoassays, and various HBV DNA amplification assays. Molecular characterizations of HBsAg‐positive/NAT‐negative samples were determined by quantitative polymerase chain reaction (qPCR) and nested PCR amplification of the basic core and precore promotor regions (295 base pairs) and HBsAg (S) region (496 base pairs).RESULTSScreening of 101,025 eligible blood donations identified 157 (0.16%, 95% confidence interval, 0.13%‐0.18%) HBsAg ELISA‐positive/NAT‐negative plasma samples; of those, 71 (45.2%) were HBsAg confirmed positive by further HBsAg testing and DNA positive by molecular tests with increased sensitivity. Of the 71, all but one was antibody to hepatitis B core antigen reactive without antibody to hepatitis B surface antigen, yielding one recent (window‐period) HBV infection. Of the remaining donations, 80 (51%) were not considered as HBV‐infected donors, and 6 (3.8%) were interpreted as indeterminate since HBsAg results were discordant with unconfirmed HBV DNA results. In the 71 confirmed positives, HBsAg levels ranged from 0.05 to 400 IU/mL and HBV DNA from 6 to 2654 IU/mL; however, the correlation between the two was weak (R2 = 0.24).CONCLUSIONFewer than half of HBsAg ELISA‐positive/NAT‐negative samples were confirmed as HBsAg positive. Our study demonstrates that in highly HBV‐endemic countries, assays with high sensitivity and specificity may be required.

COVID-19 vaccines have saved millions of lives; however, understanding the long-term effectiveness of these vaccines is imperative to developing recommendations for booster doses and other precautions. Comparisons of mortality rates between more and less vaccinated groups may be misleading due to selection bias, as these groups may differ in underlying health status. We studied all adult deaths during the period of 1 April 2021–30 June 2022 in Milwaukee County, Wisconsin, linked to vaccination records, and we used mortality from other natural causes to proxy for underlying health. We report relative COVID-19 mortality risk (RMR) for those vaccinated with two and three doses versus the unvaccinated, using a novel outcome measure that controls for selection effects. This measure, COVID Excess Mortality Percentage (CEMP), uses the non-COVID natural mortality rate (Non-COVID-NMR) as a measure of population risk of COVID mortality without vaccination. We validate this measure during the pre-vaccine period (Pearson correlation coefficient = 0.97) and demonstrate that selection effects are large, with non-COVID-NMRs for two-dose vaccinees often less than half those for the unvaccinated, and non-COVID NMRs often still lower for three-dose (booster) recipients. Progressive waning of two-dose effectiveness is observed, with an RMR of 10.6% for two-dose vaccinees aged 60+ versus the unvaccinated during April–June 2021, rising steadily to 36.2% during the Omicron period (January–June, 2022). A booster dose reduced RMR to 9.5% and 10.8% for ages 60+ during the two periods when boosters were available (October–December, 2021; January–June, 2022). Boosters thus provide important additional protection against mortality.

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