key: cord-0742363-pq5rlaml authors: Gong, Liubing; Zhang, Xu; Qu, Zhiqiang; Francis, Mark R.; Han, Kaiyi; Xu, Cuilin; Cai, Enmao; Shi, Huilin; Hou, Zhiyuan title: Public Interest in Distribution and Determinants of Influenza and Pneumonia Vaccination during the COVID-19 Pandemic: An Infodemiology and Cross-Sectional Study from China date: 2021-11-15 journal: Vaccines (Basel) DOI: 10.3390/vaccines9111329 sha: 7dd4cf1c1c7885c6aac6da197fcce8ef50682381 doc_id: 742363 cord_uid: pq5rlaml Background: Following the COVID-19 pandemic, global interest in influenza vaccines and pneumonia vaccines has increased significantly. We aimed to examine public interest in and actual market circulation of influenza and pneumonia vaccines before and after the initial outbreak of COVID-19 and estimate the coverage and determinants of influenza and pneumonia vaccination uptake following the COVID-19 pandemic. Methods: We obtained search volume data for vaccines using the Baidu search index and collected the numbers of vaccines issued from the National Institutes for Food and Drug Control. We also conducted a cross-sectional survey among 3346 adult residents to evaluate the coverage and determinants of influenza and pneumonia vaccination uptake in the Yangtze River delta, China, from 29 January to 4 February 2021. Results: Public searches and the number of vaccines issued for the influenza vaccines and pneumonia vaccines obviously increased after the initial outbreak of COVID-19. In the total sample, 12.5% were vaccinated against influenza, and 21.5% had at least one family member vaccinated against pneumonia. A minority of participants perceived that they were highly or very highly susceptible to influenza (15.9%) and COVID-19 (6.7%). A range of socio-economic factors and perceived susceptibility to COVID-19 were associated with influenza and pneumonia vaccination uptake. Conclusions: Public interest in and issued volumes of influenza and pneumonia vaccines increased nationally following the COVID-19 pandemic. Perceptions of high susceptibility to COVID-19 were associated with the uptake of the influenza and pneumonia vaccines. Targeted interventions were needed to improve vaccination coverage. Influenza and pneumococcal infections place a heavy burden on communities and healthcare systems worldwide [1] [2] [3] . It is estimated that globally, 290,000-650,000 influenzaassociated respiratory deaths occurred annually from 1999 to 2015 [2] , and pneumonia was responsible for approximately 1.52 million deaths in 2015 [4] and 1.19 million deaths in 2016 [3] . Vaccination is considered as the most effective strategy for the prevention of influenza and pneumococcal infections. According to a study from the United States, vaccination prevented a significant number of influenza-related illnesses and reduced the burden of hospitalizations and death in 2017-2018, despite the low efficacy of influenza vaccines [5] . In addition, vaccination against pneumonia in adulthood reduced the burden of community-acquired pneumonia and its associated complications [6] . However, many countries face multiple challenges including vaccine shortages, a lack of public awareness, insufficient vaccine demand, and failure to integrate influenza vaccines into the national immunization program, which lead to suboptimal vaccination coverage [7] [8] [9] [10] . For example, the influenza vaccination coverage in China was only 2% during 2004-2014 [11] . Pneumococcal vaccination coverage is also inadequate; a regional study showed that the coverage of the 23-valent pneumococcal polysaccharide vaccine (PPV23) among children and adults (above two years of age) was only 3% in Hangzhou city in 2017 [12] . In 2020, COVID-19 caused by the severe acute respiratory syndrome coronavirus 2 (SARS-CoV-2) became a pandemic worldwide. Most COVID-19 infections produce mild to moderate respiratory disease [13] . However, the constant mutations of SARS-CoV-2 could lead to recombinant variants, which will drive periodic epidemics in the years to come [14] . These spikes in COVID-19 case counts, if occurring during the months when influenza and pneumonia are prevalent [15, 16] , could place additional pressure on already burdened health care systems. Thus, many countries have taken measures to improve influenza and pneumonia vaccination coverage to mitigate the stress on their healthcare systems caused by the ongoing pandemic [16] [17] [18] [19] . Several studies have investigated the public's intention to vaccinate against seasonal influenza and pneumonia during the COVID-19 pandemic [20] [21] [22] [23] . Some of these studies have shown that the COVID-19 pandemic might positively impact the public's demand for seasonal influenza and pneumonia vaccinations [20] [21] [22] . Possible reasons for this are that influenza, pneumonia, and COVID-19 can present with similar symptoms [24, 25] , and beyond that, they share the same risk groups, proving detrimental to older persons and persons with chronic diseases [26, 27] . Therefore, the ongoing pandemic may have contributed to a higher interest in or awareness about the influenza and pneumonia vaccines in various settings. Unfortunately, there is no research on the actual uptake of influenza and pneumonia vaccination in China since it entered the normalized epidemic prevention and control phase [28] . Therefore, timely research is needed to investigate potential links between the public interest in influenza and pneumonia vaccines and the subsequent uptake of these vaccines during the COVID-19 pandemic. This study aimed to (1) compare public interest in influenza and pneumonia vaccines (using the Baidu search index) before and after the initial outbreak of the COVID-19 pandemic nationally, (2) estimate actual market circulation of influenza and pneumonia vaccines through data obtained from the National Institutes for Food and Drug Control (NIFDC) nationally, and (3) investigate the uptake and determinants of influenza and pneumonia vaccination following the COVID-19 pandemic through a cross-sectional survey in the Yangtze River delta. We conducted a cross-sectional survey among adults aged 18 years and above in the Yangtze River delta from 29 January to 4 February 2021. Three cities representing different levels of economic development, including Shanghai city, Nanjing city in the Jiangsu province, and Chizhou city in the Anhui province, were selected for the survey. Snowball sampling was employed to enroll the study participants. Based on the power analysis with 90% statistical power at 5% level of significance, the minimum sample size was estimated as 934 participants per city. We invited participants to complete a questionnaire through the Center for Disease Control and Prevention (CDC) and 4-8 Community Health Centers in each city. We encouraged participants who completed the survey to share a link to the questionnaire via social media platforms to invite their colleagues or friends to participate. In addition to the survey, we also assessed public interest in influenza and pneumonia vaccines using the Baidu search index [29] , an internet search trends compilation and analysis tool providing daily weighted search volumes for selected keyword searches on the Baidu search engine used throughout China [30] . We overlayed these data on publicly available data on the distributed volumes of influenza vaccines (during 2018-2021) and 23-valent pneumococcal polysaccharide vaccines (2018-2020) extracted from the official website of the National Institutes for Food and Drug Control (NIFDC) [31] -the official agency responsible for the issuance of biological products, including vaccines in China. The study was approved by the Institutional Review Board of the School of Public Health, Fudan University. We developed a web-based questionnaire to collect information on vaccination uptake and its associated factors for the cross-sectional survey. Additionally, the content validity of the questionnaire was assessed by experts in epidemiology and infectious diseases. Respondents could access the questionnaire through WeChat, a social media with 1.1 billion active users. Each WeChat account was allowed to fill in the questionnaire once to avoid data duplication, and only devices with Internet Protocol addresses in the chosen cities could successfully submit their responses to the questionnaire. The survey questionnaire was pilot tested and validated among ten respondents in a non-study community. It took approximately 3-5 min to complete the self-administered questionnaire, and respondents received electronic currency worth about CNY 5 (USD 0.77) as a gift after they completed the questionnaire. In total, 3354 participants answered the questionnaire independently and provided e-consent. Eight incomplete or less than 2 min responses were excluded from the analysis. Finally, 3346 participants were included in the present study, with an effective response rate of 99.8% (3346/3354). Using the Baidu search index, we collected daily search volumes for the keyword "influenza vaccine" for every flu season (June to March of the following year) during 2018-2021. In addition, we restricted Baidu search index data on pneumonia vaccine searches (using the keyword "pneumonia vaccine") from January 2018 to July 2020 to avoid COVID-19 vaccine searches, which began in August 2020. We also extracted the volumes of influenza vaccines issued during 2018-2021 and 23-valent pneumococcal polysaccharide vaccines issued during 2018-2020 from the NIFDC website. The NIFDC posts updated information on its official website about the type, manufacturer, and amounts of vaccines approved for issuance. We restricted this data extraction on influenza and pneumonia vaccines issued for adults to compare the study populations. For the cross-sectional survey, we collected basic socio-demographic on participants, including their gender, age, marital status, educational level, occupational, and annual household income. In addition, we used two questions to measure participants' vaccination behavior after the COVID-19 pandemic, "Have you been vaccinated against influenza since September 2020?" and "Have you or members in your family (including the elderly and children) been vaccinated against pneumonia since 2020?". Participants who answered "yes" to receiving an influenza vaccination were asked to select their reason for vaccination from a list of prepopulated responses. Participants' perceptions of their susceptibility to and the severity of influenza and COVID-19 were assessed in the questionnaire. Responses to these questions were collected on a five-point Likert scale with the following options: very high, relatively high, fair/unknown, relatively low, and very low. In addition, we outlined the response to the question measuring participant perceptions of the severity of COVID-19 using China's Guidance on the Diagnosis and Treatment of COVID-19 [32] , with the following options: severe, moderate, mild, asymptomatic, and unknown. We did not inquire about the participants' perceptions of the susceptibility to and severity of pneumonia as it is difficult for the general population to distinguish between COVID-19 and pneumonia [14] . All the variables measuring participants' perceptions were dichotomized for the analyses. We also assessed the participants' familiarity with influenza vaccines and their self-rated health. We calculated frequencies and percentages to describe the study sample on unweighted data from the cross-sectional survey. We then developed univariate analyses (significance level: 0.05) using the Pearson chi-square test to examine differences in influenza (since September 2020) and pneumonia (since January 2020) vaccination uptake by the different study variables. The study variables included the participant's sociodemographic characteristics, their perceptions about the susceptibility to and severity of COVID-19, and their self-rated health status. Participants' perceptions of their susceptibility to and the severity of influenza and familiarity with the influenza vaccine were only investigated in the univariate analysis for the factors associated with flu vaccination uptake. All the study variables were analyzed categorically. Finally, we performed two full multivariable logistic regressions (with the "enter" method) to examine the factors associated with influenza and pneumonia vaccination uptake, and all variables analyzed in univariate analyses were added into the corresponding models for each vaccine. The model fit of logistic regression analysis was assessed using the Hosmer-Lemeshow goodness-offit test. The findings of the multivariate analyses are presented as adjusted odds ratios (aORs) with 95% confidence intervals (CIs). We also plotted the frequency and trends of the Baidu search index (daily weighted search volumes) for and issued volumes (monthly) of influenza and pneumonia vaccines to visually describe the public interest in and actual distribution of these vaccines before and after the pandemic. All analyses were performed using IBM SPSS Statistics for Windows, version 20.0(IBM Corp, Armonk, NY, USA). The Baidu search index for the keyword 'influenza vaccine' suggested that public interest in the influenza vaccine was markedly higher, and the initiation of this interest was much earlier in the 2020-2021 flu season than the previous two seasons (Figure 1a ). Online search volumes for influenza vaccines began to rise in August 2020, peaked in early September, and again in late October 2021. In terms of vaccine supply, the issued volume of influenza vaccines for adults in the 2020-2021 season (45.5 million) was almost three times of that in 2018-2019 (16.2 million) and 2019-2020 (16.3 million). Moreover, consistent with the Baidu search index, NIFDC began approving and issuing a larger volume of flu vaccines in July 2020, also earlier than in the previous years ( Figure 1a) . For the keyword 'pneumonia vaccine', the Baidu search index sharply increased in late January 2020 and peaked on January 25 (6403), significantly higher than its usual search volume (around 800-900) ( Figure 1b) . However, it gradually decreased in early February and normalized by mid-February, except for a relatively high search volume on 25 February (3851). Thus, the public's increasing interest in the pneumonia vaccine only lasted for about a month in 2020. The total volume of 23-valent pneumococcal polysaccharide vaccines issued for adults in 2020 (16.9 million) was around twice of that in 2018 (7.0 million) and 2019 (9.2 million) ( Figure 1b) . A total of 3346 residents responded to the questionnaire with valid data (Table 1) . Participants from Shanghai, Nanjing, and Chizhou city accounted for 32.9%, 32.6%, and 34.5%, respectively. Most respondents were female (59.9%), married (81.6%), and local A total of 3346 residents responded to the questionnaire with valid data (Table 1) . Participants from Shanghai, Nanjing, and Chizhou city accounted for 32.9%, 32.6%, and 34.5%, respectively. Most respondents were female (59.9%), married (81.6%), and local registered residents (77.4%). The average age of the participants was 37.2 years, with the largest proportion aged 26-35 years (40.2%). Nearly two-thirds had obtained junior college or bachelor-level education (65.2%) and worked in government agencies or service industries (68.4%), and 56.8% had an annual household income of less than CNY 100,000 (USD 15,560). In addition, a majority of respondents considered their health status to be good (89.3%). About one-eighth of the respondents (12.5%) were vaccinated against influenza in the 2020-2021 flu season until the beginning of February 2021 (Table 1) , and nearly one-fifth (19.0%) of these vaccinated respondents reported being vaccinated because of COVID-19 ( Figure 2 ). In addition, 21.5% of families had at least one member vaccinated against pneumonia from 2020 until early February 2021 (Table 1 ). More than half of respondents considered themselves very familiar (13.6%) or relatively familiar (41.9%) with the influenza vaccine ( Figure 3 ). Only 15.9% of the respondents considered themselves highly or very highly susceptible to influenza infections. However, more than half of the respondents considered that flu infections could be very (22.2%) or relatively highly (42.0%) serious. In addition, 6.8% considered that they were highly or very highly susceptible to COVID-19 infection, and 17.8% considered that they would be moderately or severely symptomatic if infected with COVID-19. About one-eighth of the respondents (12.5%) were vaccinated against influenza in the 2020-2021 flu season until the beginning of February 2021 (Table 1) , and nearly onefifth (19.0%) of these vaccinated respondents reported being vaccinated because of COVID-19 ( Figure 2 ). In addition, 21.5% of families had at least one member vaccinated against pneumonia from 2020 until early February 2021 (Table 1 ). More than half of respondents considered themselves very familiar (13.6%) or relatively familiar (41.9%) with the influenza vaccine ( Figure 3 ). Only 15.9% of the respondents considered themselves highly or very highly susceptible to influenza infections. However, more than half of the respondents considered that flu infections could be very (22.2%) or relatively highly (42.0%) serious. In addition, 6.8% considered that they were highly or very highly susceptible to COVID-19 infection, and 17.8% considered that they would be moderately or severely symptomatic if infected with COVID-19. Table 1 presents the respondents' vaccination statuses (flu/pneumonia) by their socio-demographic and other characteristics, and the results of univariable analysis. When p < 0.05, the vaccination coverage of residents was significantly different between groups with different characteristics. For example, the p value from the Chi-square test between influenza vaccination and "familiarity with flu vaccine" was "p < 0.001", which means a significantly higher proportion of participants familiar with the flu vaccine (17.8%) were vaccinated against influenza than those unfamiliar (5.8%) in the 2020-2021 flu season (until early February). It was suggested that influenza vaccination uptake in the 2020-2021 flu season (until early February) was positively associated with familiarity with flu vaccine. Such positively associated factors also included living in Nanjing or Shanghai city (p = 0.025), having higher education (bachelor's degree or above) (p < 0.001), working in government agencies or service industries (p < 0.001), the highest (>CNY 200,000) or lowest (CNY 200,000) or lowest (