Study population
A retrospective cohort study was conducted. The study was conducted in March 2023, among preterm infants aged 0 to 7 who contracted COVID-19 for the first time, three months after the comprehensive lifting of COVID-19 protection measures in China.
After multiple discussions and revisions by senior neonatologists at the hospital, a standardized questionnaire was designed. It was then repeatedly tested by neonatologists and parents of preterm infants before final utilization to ensure consistency and reliability. The questionnaire was developed by the online survey platform “Wenjuanxing” and distributed in a WeChat group of neonatology directors in China. The questionnaire was then forwarded to parents of preterm infants aged 0–7 years.
Participation criteria were: (1) children between 3 and 7 years of age; (2) Children whose gestational age is less than 37 weeks. Children with incomplete information or who received recombinant vaccines were excluded. A total of 242 preterm infants were included in this study (Figure 1; details of how the minimum sample size was calculated are provided in Supplementary File S1, and the results of the required minimum sample size for different scenarios are provided in Supplementary Table ) S1).
Figure 1
Flowchart of this study.
This study was approved by the Ethics Committee of the Seventh Medical Center of the People’s Liberation Army General Hospital. All studies were conducted in accordance with relevant guidelines/regulations. Informed consent was obtained from all subjects involved in the study. All procedures were performed in accordance with the Declaration of Helsinki.
data collection
Demographic characteristics, gestational age ((24.9, 28) weeks, (28, 32) weeks, and (32, 37) weeks), underlying health status, COVID-19 vaccination status, COVID-19 Patient data, including the presence or absence of infectious diseases, were collected. 19 relevant outcomes (for vaccinated children, we recorded whether they had a COVID-19-related outcome 14 days after vaccination against SARS-CoV-2). Demographic characteristics included age, gender, ethnicity, living environment (urban or rural), educational background, and place of residence (i.e., eastern, central or western China) (Supplementary Table S2). Underlying health conditions include atrial septal defect (ASD), ventricular septal defect (VSD), BPD, asthma, hypersensitivity, genetic disorders, metabolic disorders, and immune deficiencies. Diagnosis of the new coronavirus infection was made through antigen testing, nucleic acid testing, and confirmation of infection in people living together at the same time.
COVID-19-related outcomes include symptomatic COVID-19, pneumonia, and some COVID-19-related symptoms (fever, high fever (i.e., highest body temperature during the course of COVID-19) temperature (39°C or higher) and decreased mental status). reactions, fatigue, muscle pain, sore throat, loss of smell, loss of taste, cough, stuffy nose, runny nose), persistent symptoms one month after recovery from COVID-19 (fatigue, dizziness, headache) , muscle pain, joint pain, dryness, etc.) Throat, sore throat, hoarseness, chest tightness, shortness of breath, cough, stuffy nose, runny nose, decreased sense of smell, decreased sense of taste, sleep disturbance, mood swings) , myocardial injury, multisystem inflammatory syndrome in children (MIS-C), hospitalization, and need for respiratory support.
statistical analysis
Preterm infants were divided into two groups according to their COVID-19 vaccination status: vaccinated and unvaccinated children. Continuous variables were summarized using mean and standard deviation. Categorical variables were expressed as numbers and percentages. The main analysis considered age, gender, ethnicity, urban status, educational background, place of residence, and underlying health status as covariates.
Entropy balancing (EB) is used to compare vaccinated and unvaccinated children with the aim of properly estimating the effect of vaccination against SARS-CoV-2 on symptomatic COVID-19 and related symptoms. were employed to balance the covariates of 16. Standardized mean differences (SMDs) were calculated to assess the level of covariate balance between vaccinated and unvaccinated children. SMD < 0.1 indicates good balance17. Weights were derived based on covariates through EB.
The primary outcome of interest was symptomatic COVID-19 infection. The effect of SARS-CoV-2 vaccination against symptomatic COVID-19 was investigated by building a modified Poisson regression model combined with EB using EB-derived weights for each observation 18, 19. In addition, at least 10 other COVID-19-related outcomes were used as secondary outcomes. The impact of COVID-19 vaccination on these outcomes was investigated using modified Poisson regression models or logistic regression combined with EB when appropriate. Logistic regression models use rare (usually < 10%) バイナリ結果の影響要因を評価するために一般的に使用されるアプローチです。まれな結果の場合、ロジスティック回帰モデルから推定されるオッズ比 (OR) はリスク比 (RR) に近づきます。ただし、まれではない結果では、OR の値が RR の値と異なる場合があります。この場合、修正ポアソン回帰モデルは、RR18、19 を推定するためのより良い代替手段です。したがって、この研究では、ワクチン接種済みの子供とワクチン接種を受けていない子供を比較した結果のRRとORが、それぞれ修正ポイズン回帰モデルとバイナリロジスティック回帰モデルを使用して推定されました。 />
To test the robustness of our results, we conducted a sensitivity analysis excluding the covariate of children’s educational attainment. All analyzes were performed using R (version 4.3.1). Two-tailed P < 0.05 was considered statistically significant.
