Maternal immunization is a highly effective public health strategy. The administration of vaccines to pregnant women increases the level of specific transplacental maternal antibodies, thereby protecting the pregnant fetuses, newborns, and early-life infants from the corresponding pathogens. Currently, maternal immunization strategies for pertussis, influenza, etc. have been widely used worldwide, and positive results have been achieved in preventing respiratory syncytial virus infection in infants. This article reviews different designs of maternal vaccination clinical studies, including randomized controlled trials, cohort studies, case-control studies, and surveillance data studies. It summarizes the strengths and weaknesses of different study approaches and discusses the application of maternal immunization strategies to provide a reference for developing maternal immunization research in China.

Maternal immunization is a highly effective public health strategy. The administration of vaccines to pregnant women increases the level of specific transplacental maternal antibodies, thereby protecting the pregnant fetuses, newborns, and early-life infants from the corresponding pathogens. Currently, maternal immunization strategies for pertussis, influenza, etc. have been widely used worldwide, and positive results have been achieved in preventing respiratory syncytial virus infection in infants. This article reviews different designs of maternal vaccination clinical studies, including randomized controlled trials, cohort studies, case-control studies, and surveillance data studies. It summarizes the strengths and weaknesses of different study approaches and discusses the application of maternal immunization strategies to provide a reference for developing maternal immunization research in China.

Objective: To analyze the stress-strain characteristics of the polycaprolactone (P C D meniscus scaffold in the knee joint, and to evaluate its feasibility as an implant material. Methods: The magnetic resonance imaging (MRI) scan of volunteer knee joints was used to obtain the planar image data. A three-dimensional finite element model including the femur, tibia, fibula, femoral condyle and tibial plateau articular cartilage, medial and lateral menisci, and ligaments was established. The validity of the model was verified by calculating the contact area of the tibial plateau and comparing with the previous literatures. On this basis, the three-dimensional finite element model of the knee joint after medial meniscectomy was established by deleting the medial meniscus unit and node of the normal knee joint. The knee joint model was established after replacement of the PCL meniscus. The changes of meniscal displacement and contact pressure in three types of knee joint models under 1 400 N femoral axial vertical pressure and the changes of compressive stresses on the femoral articular cartilage and tibial plateau articular cartilage were compared Results: The displacements of the medial and lateral menisci of the healthy knee joint under the axial compression load of 1 400 N femur were 0. 83 and 1. 76 mm, respectively. The displacements of the medial and lateral meniscus of the PCL model were 1. 15 and 2. 20 mm, respectively. Under the same load, the maximum compressive stresses of the healthy knee joint on the medial and lateral cartilage of the tibial plateau were 2. 5 and 1. 7 MPa, respectively; the maximum compressive stresses on the medial and lateral femoral articular cartilage were 2. 7 and 2. 1 MPa, respectively. In the medial meniscus complete resection model, the maximum compressive stresses on the medial and lateral cartilage of the tibial plateau articular cartilage were 9. 0 and 7.0 MPa, respectively, which were normal increase of 260.0% and 311.7%, respectively, compared with the healthy model; and the maximum compressive stresses on the medial and lateral femoral condylar cartilage were 8. 5 and 7. 8 MPa, respectively, which were 214. 8% and 271. 4% higher than the normal models, respectively. When the medial meniscus was replaced with the PCL scaffold, the maximum compressive stresses on the medial and lateral cartilage of the tibial plateau articular cartilage were 2. 7 and 1. 8 MPa, respectively, which were 8. 0% and 5. 9% higher than those of the healthy knee joint model, respectively. The maximum compressive stresses on the medial and lateral femoral condyle cartilage were 3. 0 and 2. 2 Mpa, respectively, which were 11. 1% and 4. 8% higher than the normal model. Concluson: The three-dimensional finite element model of knee joint of PCL material has good biomechanical ability, which can reduce the stress of articular cartilage of femoral condyle and tibial plateau after meniscectomy and achieve the purpose of protecting the articular cartilage.