1. Introduction
Pregnant women and young children, especially young infants, are at greater risk of severe disease or complications when infected with seasonal influenza (influenza) and pertussis (whooping cough) [
1]. Influenza and pertussis spread easily from person to person, mainly through droplets produced by coughing or sneezing [
2]. Vaccination of pregnant women is likely to be the most cost-effective additional strategy for preventing pertussis in infants too young to be vaccinated, and it appears to be more effective and favorable than cocooning [
3,
4]. The World Health Organization (WHO) has recommended vaccination against influenza in pregnant women since 2005 [
5]. In 2014, the Chinese Advisory Committee on Immunization Practice updated the guidelines for the application of the seasonal influenza vaccine (SIV), which recommended SIV vaccination of pregnant women as a high-priority group [
6]. The DTP (combined diphtheria, tetanus, and pertussis) vaccine has been included in the China National Immunization Program since 1978, and now, the immunization schedule of the DTaP (combined diphtheria, tetanus, and acellular pertussis) vaccine is at 3, 4, 5, and 18 months for children [
7,
8]. However, in China the pertussis-containing vaccines were not applicable to teenagers, adults, and pregnant women [
9]. In 2021, expert consensus based on the China Pertussis Initiative suggested to improve the immunization program and strategy of the pertussis vaccine in China, including by exploring how to carry out booster immunization for school-age children, adolescents, adults, and pregnant women on the basis of existing immunization schedules [
10]. Vaccination against influenza and pertussis is routinely recommended during pregnancy in several countries [
11,
12]. This prevention strategy of maternal vaccination has hardly been carried out in China for either influenza or pertussis, and guidelines specifically for pregnant woman are usually not included in the information accompanying the vaccines [
13,
14].
In 2017, the greatest number of cases of pertussis were reported in India (23,766), Germany (16,183), Australia (12,114), and China (10,390) [
15]. In China, the pertussis incidence rate appears to be going up, especially in the population of children less than one year of age, and about 70% of children do not start the DTaP vaccination schedule or have not completed primary immunization [
9]. Guizhou province is an economically underdeveloped province of China, located in the southwestern area. In recent years, there have been frequent outbreaks of influenza and family-scattering cases reported in this area [
16,
17,
18]. According to influenza surveillance sentinel data, the positive detection rate for influenza virus nucleic acid was as high as 30.79% in the reported cases of influenza-like illness in the influenza surveillance years of 2017–2018 [
19]. Meanwhile, the pertussis incidence rate showed a significant upward trend, and the incidence rate in 0-year-old children was highest, reaching 91.2/100,000 between 2017 and 2019 in Guizhou province. Among the reported pertussis cases, 80% of whooping cough patients had not completed the primary series of three doses of DTaP vaccination, mainly because they were too young at the time of the onset month, namely, below the age of 5 months that is set for receiving the primary three doses in the national recommended immunization schedule of China [
20]. The vaccines against influenza and pertussis given at birth are not applicable until this age. To protect infants, especially in the first few months of life, from influenza and pertussis, maternal vaccination is optimal.
Currently, the influenza vaccine is not included in the National Immunization Program, and it is optional and self-funded for the populations in Guizhou province, China. In recent years, the overall coverage rate of the SIV has risen in some areas in China [
21,
22], but it is still low in Guizhou province. In the 2020–2021 influenza season, the SIV vaccination rate of children aged 6 months to 5 years in Guizhou province was 16.27%, and the influenza vaccination rate of elderly people aged 65 years and over was 2.15% [
23,
24]. Recently, a survey showed that people aged 18-65 in mainland China had low knowledge levels on influenza and influenza vaccination [
25]. Additionally, to our knowledge, pertussis knowledge was also limited even among healthcare workers [
26]. However, the knowledge status is unknown amongst pregnant women, and there is no comparison of knowledge levels between influenza and pertussis and the role this plays in the willingness to vaccinate.
To explore vaccination strategies against pertussis and influenza, the vaccination attitudes and choices of pregnant women require special attention. Thus, a survey was conducted among pregnant women in Guizhou province from January to February 2022 to improve understanding of and address gaps in their knowledge. The aims of this study were: (1) to investigate disease common knowledge and attitudes toward pertussis and influenza vaccinations among pregnant women; (2) to explore the role of disease common knowledge in the willingness to receive vaccinations; and (3) to identify the factors influencing these knowledge levels.
2. Methods
2.1. Study Institutions
The information from the medical institutions in Guizhou province was obtained from the standard coding management system of China’s disease prevention and control information system. In total, 484 general hospitals, maternal and child healthcare hospitals, and traditional Chinese medicine (general) hospitals are registered under the health administration departments in Guizhou province. Of these, 15 hospitals were randomly selected through the method of simple random sampling using SPSS 22.0 software (IBM Corp. in Armonk, NY, USA). After a preliminary investigation of the medical institutions’ service content, 11 hospitals were included in the target organizations that carried out obstetrics and antenatal examination services. Among the 11 hospitals, 5 were state-owned and 6 were private, 1 was a tertiary medical institution, 5 were secondary hospitals, and 5 were first-level and below medical institutions. The eleven hospitals are located in the nine counties of Guizhou province, including five counties in the north (counties: Daozhen, Renhuai, Chishui, Hezhang, Qixingguan) and four counties in the center and south (counties: Xiuwen, Guanling, Kaili, Xingyi).
2.2. Study Subjects
From 20 January to 9 February 2022, the survey was carried out in the 11 hospitals, and pregnant women who visited the gynecology and obstetrics clinics were included in the survey with their informed consent. Meanwhile, the survey questionnaire was administered to the electronic contact groups of pregnant women in the hospitals. The inclusion criteria were women undergoing pregnancy, participation in this study for the first time, and informed consent. The exclusion criteria were an incorrect answer to a choice question (for example, for “What holiday is 1st October in China?”, the right answer is National Day) and other obvious errors in demographic information. Approval for the protocol was obtained from the Ethics Committee of the Guizhou Provincial Center for Disease Control and Prevention.
2.3. Survey Questionnaire and Questions
The survey questionnaire was self-developed. First, it was modified through pre-experimental tests on six women who were pregnant or new mothers. Second, it was tested on participants in a secondary hospital and a private hospital, where 59 eligible questionnaires were received. According to the above pilot tests, minor changes were made and those results were not included in the sample of the survey.
The questionnaire collected the following data items: (1) Common knowledge about pertussis and influenza, including six items: ever heard of it; it is infectious; main source of infection; main mode of infection; main clinical manifestations; preventable vaccine. (2) Willingness to be vaccinated against pertussis and influenza at different life stages, including: vaccinate during pregnancy; vaccinate baby at own expense; vaccinate postnatally; recommend family households to get vaccinated; give baby free vaccination. (3) The basic statuses of subjects, including: birthday; gestational weeks; bearing children; educational level; occupation; location city/county name; registered residence type; ethnicity; pre-existing diseases; pregnancy-induced diseases; monthly household income per capita; vaccination history in the year before pregnancy; and so on.
2.4. Data Collection Tools
The survey questionnaire was established on the platform of Wen Juan Xing (Wen Juan Xing; Changsha Ranxing Information Technology Co., Ltd., Changsha, China). The pregnant women filled in the questionnaire by scanning the code using WeChat software (Tencent; Shenzhen, China) on their mobile phones. The data were collected by the Wen Juan Xing platform.
2.5. Knowledge Level
For comparison of the knowledge status between influenza and pertussis, the items of the questionnaire should stay comparable. Both influenza and pertussis are vaccine-preventable infectious diseases. We defined the common conceptions of infectious diseases as common disease knowledge to evaluate the knowledge levels for influenza and pertussis. The knowledge level was determined using six general questions on the disease and its vaccine (see
Section 2.3. Survey Questionnaire and Questions). Each correctly marked item of the questionnaire added +1 to the sum score, whereas any incorrect one or an answer of do not know added 0. The knowledge level was calculated by the sum of the items’ scores. When comparing the influencing factors, we split the knowledge sum scores at the median numbers and divided them into low- and high-score levels.
2.6. Sample Size
This research was a cross-sectional survey. The primary objective of this research was to obtain the knowledge level about influenza and pertussis among pregnant women. This cross-sectional survey sample-size calculation formula was used:
where
n is the size of the sample,
α is the probability of type Ⅰ error,
σ is the standard deviation, and
δ is the margin of error. According to the results of the pre-experimental tests, the mean (SD) of knowledge scores for pertussis was 3.44 (1.86), and the standard error was 0.24. We used
α = 0.05,
σ = 2.0, and
δ = 0.2 in the formula, and the calculated sample size was 385 cases. Considering the invalid questionnaires and the losses during the survey, the sample size was expanded by 20%, and thus, to
n = 462. The upward rounding sample size was 500.
2.7. Data Statistics
Categorical variables were described as proportions, and continuous variables were described as mean (SD) or median (IQR). To compare the distribution of two categorical data and three categorical data among two-paired samples, the McNemar test and Wilcoxon signed-rank test were used, respectively. Additionally, the Friedman test was used to compare categorical distribution among multiple paired samples. To explore the correlation between knowledge levels and vaccination willingness, Spearman’s correlation analysis was used. To explore the factors influencing the knowledge levels, the chi-square test and binary logistic regression were used with stepwise backward regression (α In = 0.05, α Out = 0.10). Depending on the univariate analysis results, variables with p ≤ 0.1 were chosen mainly for the multivariate analysis. To understand how the factors changed when considering only pregnant women working in nonmedical institutions, a subgroup analysis among the pregnant women working in nonmedical institutions was carried out using binary logistic regression as above. Data were analyzed by SPSS 22.0 software. Any p-values < 0.05 (bilateral) were considered to indicate statistically significant differences.