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.

Background In recent years, due to the increasing number of e-cigarette users, the health problems caused by e-cigarettes are attracting people's attention. Objective This study is designed to analyze the characteristics of e-cigarette-related research literature, research trends, and its toxicity from 2010 to 2020 through bibliometric analysis to provide a reference for studies related to the health effects of e-cigarettes. Methods The studies related to e-cigarettes in the Web of Science were retrieved, and the functions of "Creating citation report" and "Analyzing retrieval results" provided by Web of Science were used to conduct statistical analysis on publication time, literature type, publication source, country/region, research interests, research institution, etc. With the help of the knowledge function of CiteSpace V5.7, author collaboration, organization cooperation, keyword co-occurrence and keyword emergence, and reference co-citation were visualized. Results A total of 3094 studies related to health risks of e-cigarettes (public health) wereretrieved from 2010 to 2020, and the number of articles published between 2018 and 2020 accounted for 54.7% of total number. The top research institutions were from the United States (68.0%), the United Kingdom (7.6%), and Canada (6.1%). The most published author is King BA (67). The journal that published the most relevant studies was Nicotine Tobacco Research (536). The hot topics of e-cigarette research included "socioeconomic patterning," "multiple healthy behaviors," "expressive suppression emotion regulation strategies," "smoking cessation intervention studies" and "computer-delivered brief intervention". The burst intensity of keywords "cigarette smoking" was the highest, reaching 24.2. Between 2010 and 2020, the keywords "Nicotine dependence" and "Disease" emerged for the longest period of five years. "Policy" was the latest high-frequency word. The literature "Levels of selected carcinogens and toxicants in vapour from electronic cigarettes" was cited for the highest frequency, totaling 266 times. Conclusion The number of articles published has notably increased in 2018-2020, suggesting that researchers are paying attention to the health risks of e-cigarettes worldwide. The United States leads the world in the research of e-cigarette health risks. The future research direction will be focused on e-cigarette policy.