Sample size calculation for complex clinical trials with survival endpoints

Sample size estimation is important in planning clinical trials. The purpose of this paper is to describe features and use of SIZE, a comprehensive computer program for calculating sample size, power, and duration of study in clinical trials with time-dependent rates of event, crossover, and loss to follow-up. SIZE covers a wide range of complexities commonly occurring in clinical trials, such as nonproportional hazards, lag in treatment effect, and uncertainties in treatment benefit. The use of SIZE is illustrated by several hypothetical examples as well as applications to real study designs, each featuring a statistical issue.     

天津市男性浴池男男性行为人群HIV新发感染及影响因素分析

目的 分析天津市浴池MSM的HIV新发感染及其影响因素，为对浴池MSM采取相应的预防干预措施、降低HIV感染提供依据。方法 以在男性浴池寻找性伴、最近1年与同性发生过插入性口交或肛交的男性为研究对象，2011年3月至2021年12月建立开放式队列，完成HIV检测和基线调查，并进行随访和检测。调查内容包括人口学、艾滋病相关行为学信息。比较单次检测组和多次检测组的区别，计算阳性率和多次检测组的新发感染率，并应用Cox比例风险回归模型分析多次检测组HIV新发感染率的影响因素。采用EpiData 3.02软件建立数据库，采用SAS 9.4软件进行统计学分析。结果 研究期间共检测12 195人次，包括研究对象7 151人，以≥30岁（70.18%）和外地户籍（61.32%）为主，年龄范围为16~82岁，年龄M（Q₁，Q₃）为36（28，48）岁，其中检测阳性547人。与单次检测组相比，多次检测组的本地户籍、已婚/同居的比例较高，最近6个月发生肛交、接受同伴教育和最近1年被诊断患过性病的比例均较高，最近6个月发生同性性行为坚持使用安全套的比例较低。研究期间阳性率为7.65%（95%CI：7.00%~8.00%）。HIV阳性率由2011年的12.58%下降到2021年的3.31%。将多次检测组纳入开放式队列1 740人，累计随访时间为4 688.61人年，期间共新发HIV感染144人。新发感染率为3.07/100人年（95%CI： 2.57/100人年~3.57/100人年）。多因素Cox比例风险回归模型分析结果显示，外地户籍者（aHR=1.32，95%CI：1.19~1.45）和最近6个月与同性发生群交者（aHR=1.18，95%CI：1.02~1.36）HIV新发感染的风险更高。结论 天津市男性浴池MSM普遍存在群交等不安全性行为，仍需要加强宣传和干预工作，并与MSM社会组织加强合作开展男性浴池MSM同伴教育和HIV主动检测工作，并探索新的方法在MSM中降低HIV新发感染。     

Construction of an inhalable recombinant M2e-FP-expressing Bacillus subtilis spores-based vaccine and evaluation of its protection efficacy against influenza in a mouse model

Influenza A virus (IAV) is a deadly zoonotic pathogen that remains a burden to global health systems despite continuous vaccinations, indicating the need for an improved vaccine strategy. In this work, we constructed a new recombinant influenza vaccine using Bacillus subtilis spores expressing M2e-FP protein (RSM2eFP) and assessed its potency and efficacy in BALB/c mouse immunized via aerosolized intratracheal inoculation (i.t.) or intragastric (i.g.) administration. Immunization via i.t. route conferred 100 % protection against 20 × LD₅₀ A/PR/8/34 (H1N1) virus compared with only 50 % via the i.g. route. Even when challenged with 40 × LD₅₀ virus, the RSM2eFP vaccine immunized via i.t. provided 80 % protection. Consistently, i.t. inoculation of RSM2eFP spore vaccine induced a stronger lung mucosal immune response and a greater cellular immune response than i.g. administration, as indicated by the high production of IgG and SIgA. In addition, the RSM2eFP spore vaccine diminished the yield of infectious virus in the lung of mice immunized via i.t. These results suggest that i.t. immunization of the RSM2eFP spore vaccine may be a promising strategy for the development of mucosal vaccines against IAV infections.     

Quantitation of strain-specific hemagglutinin trimers in mosaic quadrivalent influenza nanoparticle vaccine by ELISA

An enzyme linked immunosorbent assay (ELISA) method was developed to analyze the assembly of a tetravalent mosaic influenza nanoparticle (NP) vaccine, Flumos-v1, consisting of hemagglutinin trimers (HAT) from H1 (A/Idaho/07/2018), H3 (A/Perth/1008/2019), HBV (Vic-B/Colorado/06/2017) and HBY (Yam-B/Phuket/3073/2013) strains. The sandwich ELISA assay used lectin from Galanthus nivalis as a universal capture reagent for all HAT strains and specific monoclonal antibody (mAb) to detect corresponding hemagglutinin antigen. The mAb binding of HATs incorporated into NPs diverged from those for single HAT solutions, resulting in inaccurate quantitation of assembled HATs. An optimized zwittergent treatment was used to fully dissociate the influenza NP and aligned binding activities in each pair of single HAT and dissociated HAT from NP. The dissociated HATs were then quantified against their corresponding HAT standard solutions for three development lots of FluMos-v1 vaccine and the assembly ratio of all four HATs was calculated. The molar ratio of different HATs incorporated into this quadrivalent NP vaccine was consistent and determined as H3:H1: HBV: HBY ∼ 1.00:0.92:0.96:0.87, which was close the expected 1:1:1:1 ratio and confirmed a proper assembling of multivalent NP.     

Mild and asymptomatic influenza B virus infection among unvaccinated pregnant persons: Implication for effectiveness of non-pharmaceutical intervention and vaccination to prevent influenza

BackgroundWe estimated symptomatic and asymptomatic influenza infection frequency in community-dwelling unvaccinated pregnant persons to inform risk communication.MethodsWe collected residue sera from multiple antenatal-care blood draws during October 2016–April 2017. We determined influenza infection as seroconversion with ≥ 4-fold rise in antibody titers between any two serum samples by improved hemagglutinin-inhibition assay including ether-treated B antigens. The serology data were linked to the results of nuclei acid testing (rRT-PCR) based on acute respiratory illness (ARI) surveillance.ResultsAmong all participants, 43 %(602/1384) demonstrated serology and/or rRT-PCR evidenced infection, and 44 %(265/602) of all infections were asymptomatic. ARI-associated rRT-PCR testing identified only 10 %(61/602) of total infections. Only 1 %(5/420) of the B Victoria cases reported ARI and had a rRT-PCR positive result, compared with 33 %(54/165) of the H3N2 cases. Among influenza ARI cases with multiple serum samples, 19 %(11/58) had seroconversion to a different subtype prior to the illness.ConclusionsThe incidence of influenza B infection in unvaccinated pregnant persons is under-estimated substantially. Non-pharmaceutical intervention may have suboptimal effectiveness in preventing influenza B transmission due to the less clinical manifestation compared to influenza A. The findings support maternal influenza vaccination to protect pregnant persons and reduce consequent household transmission.     

Cellular and humoral responses to an HIV DNA prime by electroporation boosted with recombinant vesicular stomatitis virus expressing HIV subtype C Env in a randomized controlled clinical trial

BackgroundHIV subtypes B and C together account for around 60% of HIV-1 cases worldwide. We evaluated the safety and immunogenicity of a subtype B DNA vaccine prime followed by a subtype C viral vector boost.MethodsFourteen healthy adults received DNA plasmid encoding HIV-1 subtype B nef/tat/vif and env (n = 11) or placebo (n = 3) intramuscularly (IM) via electroporation (EP) at 0, 1, and 3 months, followed by IM injection of recombinant vesicular stomatitis virus encoding subtype C Env or placebo at 6 and 9 months. Participants were assessed for safety, tolerability of EP, and Env-specific T-cell and antibody responses.ResultsEP was generally well tolerated, although some device-related adverse events did occur, and vaccine reactogenicity was mild to moderate. The vaccine stimulated Env-specific CD4 + T-cell responses in greater than 80% of recipients, and CD8 + T-cell responses in 30%. Subtype C Env-specific IgG binding antibodies (bAb) were elicited in all vaccine recipients, and antibody-dependent cell-mediated cytotoxicity (ADCC) responses to vaccine-matched subtype C targets in 80%. Negligible V1/V2 and neutralizing antibody (nAb) responses were detected.ConclusionsThis prime/boost regimen was safe and tolerable, with some device-related events, and immunogenic. Although immunogenicity missed targets for an HIV vaccine, the DNA/rVSV platform may be useful for other applications.Trial registration.Clinicaltrials.gov: NCT02654080.