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Abstract
Objectives We studied time trends in seasonal influenza vaccination and associations with socioeconomic and health-related determinants in Switzerland, overall and in people aged ≥65 years.
Design Three cross-sectional surveys.
Participants Individuals who participated in the Swiss Health Surveys 2007, 2012 and 2017. We calculated the proportion reporting influenza vaccination in the last 12 months, and performed multivariable logistic regression analyses.
Results We included 51 582 individuals in this analysis. The median age was 49 years (IQR 25–64), and 27 518 were women (53.3%). The proportion of reporting a history of influenza vaccination overall was 31.9% (95% CI 31.4 to 32.4); and dropped from 34.5% in 2007 to 28.8% in 2017. The uptake of vaccination within the past 12 months was 16% in 2007 and similar in 2012 and 2017 (around 14%). In people with chronic disease, uptake dropped from 43.8% in 2007 to 37.1% in 2012 and to 31.6% in 2017 (p<0.001). In people aged ≥65 years, uptake dropped from 47.8% in 2007 to 38.5% in 2012 to 36.2% in 2017 (p<0.001). In logistic regression, self-reported vaccination coverage decreased in the 65–75 years old (adjusted OR (aOR) 0.56, 95% CI 0.48 to 0.66 between 2007 and 2012; aOR 0.89, 95% CI 0.77 to 1.03 between 2012 and 2017). Uptake was positively associated with the ≥65 age group, living in French-speaking and urban areas, history of smoking, bad self-reported health status, private/semiprivate health insurance, having a medical profession and having any underlying chronic disease.
Conclusion Influenza vaccination coverage was low in older and chronically ill persons. Significant efforts are required in preparing for the influenza season 2020/2021 to reduce the double burden of COVID-19 and seasonal influenza. These efforts should include campaigns but also novel approaches using social media.
- infectious diseases
- public health
- epidemiology
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Strengths and limitations of this study
The Swiss Health Survey is a nationwide, representative survey that is repeated every 5 years using the same sampling methodology.
Data analysis of the Swiss Health Survey 2007, 2012 and 2017 focussing on influenza vaccine uptake overall and in the age group ≥65 years in Switzerland.
We calculated per cent of people reporting having been vaccinated, analysed time trends and associations between vaccination status and sociodemographic and health-related factors.
The analyses were weighted and adjusted for a range of potential confounders, which did not substantially change the results.
Influenza vaccination status is self-reported in the Swiss Health Survey and the reliability of the data is not ascertained.
Introduction
Seasonal influenza is pandemic, and a challenge for surveillance, control and treatment.1 Worldwide, it causes 3–5 million cases of severe illness each year and kills 250 000–500 000 people,2 particularly infants, the elderly and the chronically ill. In Switzerland, influenza is responsible for 111 000–331 000 medical consultations yearly and 1000–5000 hospitalisations.3 The current COVID-19 pandemic shows the impact of respiratory viruses on the burden of infectious diseases and the importance of vaccines in the control of viral respiratory diseases.4 5
In 2003, the World Health Assembly adopted a resolution urging member states to reach a target for uptake of influenza vaccines of 75% among people at high risk by 2010.6 The Federal Office of Public Health in Switzerland has vaccine recommendations in place since 2007, which target mainly elderly people, but also those with chronic illnesses (including children older than 6 months), premature infants, pregnant women, residents of long-term healthcare facilities and those are in regular contact with vulnerable populations.7
We earlier analysed the data from the Swiss Health Survey 2007 and 2012 and showed that overall influenza vaccine uptake in Switzerland decreased from 2007 to 2012.8 To examine recent trends and associations of sociodemographic characteristics and health-related factors with influenza vaccination practices in Switzerland, we analysed the data from the most recent nationally representative health survey, in 2017, and compared the results with those from 2012 and 2007.
Material and methods
Survey sample
The cross-sectional Swiss Health Survey has been conducted every 5 years since 1992 by the Swiss Federal Statistical Office (SFSO). The survey is a multistage probability sample drawn from all residents not living in institutions in Switzerland.8 9 Conducted between January and December of the year, the survey collects data using computer-assisted telephone interviews and self-completed questionnaires.
We compared the data set from 2017 with the data from 2012 and 2007 and only used survey data from the written forms. We excluded the telephone interviews because they were shorter and did not include all the questions. We included a total of 51 582 people who responded to a written questionnaire; 14 393 responded in 2007, 18 357 in 2012 and 18 632 in 2017.
Data collection and definitions
From all three surveys, we extracted data on influenza vaccination within the past 12 months.9
The questionnaire collected demographic and socioeconomic as well as health-related information (table 1) on chronic diseases such as diabetes, cancer, lung, cerebrovascular and cardiovascular disease. The basic health insurance is mandatory in Switzerland and provides cover for illness, maternity, and accidents, offering the same range of services to all insured people.10 The respondents’ health insurance plan regarding coverage in case of hospitalisation (private, semiprivate, or general ward), free choice of physicians and coverage of complementary medicine (including acupuncture, traditional Chinese medicine, homoeopathy, and osteopathy) in the past 12 months was recorded as well.
Percent of people reporting having been vaccinated for influenza in the last 12 months in Switzerland, 2007, 2012 and 2017, overall and among people ≥65 years old
Pregnancy was recorded as current pregnancy among women 15–49 years old. Current chronic lung diseases included asthma, chronic bronchitis and emphysema. Diabetes was defined by the use of any diabetic drug, cardiovascular disease by the use of any heart medication, and all other chronic diseases were recorded as self-reported. We defined any chronic disease as the presence of at least one of the mentioned diseases. Healthcare workers were defined as individuals reporting profession in the healthcare system.
Cantons are the administrative subdivisions of Switzerland (see figure 1).
Geographical distribution (by canton) of people reporting influenza vaccination in the last 12 months in Switzerland, 2007 to 2017. (A) Overall; (B) people aged ≥65 years. na, not applicable (no. of respondents <100).
Statistical analysis
For each of the three survey years we calculated the proportions (overall and ≥65 years) that reported having been vaccinated within the last 12 months. We estimated associations between vaccination status and sociodemographic and health-related factors. We included an interaction term with the year of survey and the variable of interest in multivariable logistic regression models. We used the SFSO’s survey weights and reported all proportions and unadjusted and adjusted OR (aOR) with the corresponding 95% CIs derived from robust SE calculations (table 2). All analyses were performed in Stata (V.15.1).
Factors associated with the temporal change (between 2007, 2012 and 2017) in self-reported influenza vaccination status in the last 12 months in Switzerland, 2007 to 2012 and 2012 to 2017, overall among people aged ≥65 years
We visualised changes in the frequency of vaccination uptake, and geographical distributions of the population that reported vaccination for influenza at the cantonal level using ArcGIS V.10.5 (Redlands, California, USA).
Results
Trends of influenza vaccinations over time
The proportion of survey participants reporting a history of influenza vaccination overall was 31.9% (95% CI 31.4 to 32.4), having dropped from 34.5% in 2007 to 28.8% in 2017. The proportion reporting vaccination within the past 12 months was 16.4% (95% CI 15.6 to 17.2) in 2007, dropped to 14.1% (95% CI 13.5 to 14.8) in 2012, and remained at this level in 2017 (14.4%, 95% CI 13.8 to 15.0, p<0.001, table 1). Among those ≥65 years old, the principal target population of the Swiss recommendations,7 vaccination in the past 12 months dropped from 47.8% (95% CI 45.7 to 49.9) in 2007 to 38.5% (95% CI 36.6 to 40.5) in 2012, and 36.2% (95% CI 34.6 to 37.9) in 2017 (p<0.001). For those with any chronic disease, another at-risk population, the frequency of influenza vaccination dropped from 43.8% (95% CI 40.9 to 46.8) in 2007 to 37.1% (95% CI 34.6 to 39.7) in 2012, and further to 31.6% (95% CI 29.7 to 33.6) in 2017. Similarly, a decrease in vaccine uptake was seen in people with poor self-reported health status (39.4%, 33.1% and 27.0%, figure 2).
Temporal trends of selected groups of people reporting influenza vaccination in the last 12 months in Switzerland, comparing 2007 to 2017. Percent of people reporting having been vaccinated and the 95% CIs are presented. Good health: self-reported health status good and very good; poor health: self-reported health status bad and very bad; with chronic disease: any chronic illness.
From 2007 to 2012 the self-reported influenza vaccination in the last 12 months decreased in age group 15–19 years (aOR 0.51, 95% CI 0.27 to 0.99) but increased from 2012 to 2017 in the younger age groups (eg, aOR 1.59, 95% CI 0.92 to 2.74 in the 15–19 years age group; aOR 1.19. 96% CI 0.84 to 1.69 in the 20–29 years age group, figure 2 and table 2). In contrast, it decreased in the 65–75 years old between 2007 and 2017 (aOR 0.56, 95% CI 0.48 to 0.66 for 2007–2012; aOR 0.89, 95% CI 0.77 to 1.03 for 2012–2017, table 2). The p value from the test for an interaction between period and age group was 0.01 for 2007–2012 and 0.051 for 2012–2017. In pregnant women, an increase of influenza vaccination was observed between 2007 and 2012 (aOR 4.43, 95% CI 0.96 to 20.42, p=0.02), with no further increase between 2012 and 2017 (aOR 0.94, 95% CI 0.36 to 2.47, p=0.45). The temporal trends over the period 2007–2012 and 2012–2017 were not associated with age, language region, urban/rural setting, citizenship, any chronic disease, smoking status, use of complementary medicine or type of hospital stay insurance (p>0.05, table 2).
Influenza vaccination status in different population groups
In all three surveys, self-reported influenza vaccination in the last 12 months was highest in the age group ≥65 years, and also higher in urban settings, among Swiss citizens, former smokers and in persons with supplemental health insurance (table 1). In all three surveys, the proportion of self-reported influenza vaccination was higher in the French-speaking and Italian-speaking region compared with the German region. Persons with chronic diseases were more frequently vaccinated for influenza, with uptake ranging from around 20% to 57% depending on age group and type of chronic disease. A lower proportion of self-reported vaccination was observed in ages 15 years to 50 years (range 4%–9%), current smokers, and person who reported their health status as very good. The regional differences in the vaccination status in the last 12 months in the overall population and the ≥65 age group are shown in figure 1A, B.
Individual and health system factors associated with the influenza vaccination status
In all three surveys, influenza vaccination in the last 12 months was positively associated with age 65 years or older, living in French-speaking and urban areas, having a tertiary education, history of smoking, bad self-reported health status, private/semiprivate hospital stay insurance, being a healthcare worker and having any underlying chronic disease. Use of any complementary medicine therapy was negatively associated with influenza vaccination (aOR 0.72, 95% CI 0.67 to 0.80). We found no association with sex, body mass index or non-Swiss citizenship (table 3). Similar findings were observed when analysing only participants’ ≥65 years old. Online supplemental table 1 shows unadjusted and aORs of the associations between self-reported vaccination for influenza in the last 12 months and sociodemographic characteristics and health-related factors.
Supplemental material
Associations of having been vaccinated for influenza in the last 12 months with sociodemographic characteristics and health-related factors (as compared with no vaccination) in Switzerland, 2007 to 2017, overall and among people ≥65 years old
Discussion
Progress toward the WHO target of 75% vaccination coverage among high-risk groups has not only stalled in Switzerland, some of the gains made in earlier years were lost by 2017. Of particular concern is that the self-reported seasonal influenza vaccination rate among elderly persons declined from 47.8% in 2007 to 38.5% in 2012, and declined further to 36.2% in 2017. People at risk due to underlying chronic diseases reported coverage of influenza vaccination of 31.6% in 2017. Overall, after declining from 16.4% in 2007 to 14.1% in 2012, coverage in Switzerland was, with 14.4%, similar in 2017.
A decline in influenza vaccine coverage in recent years has been observed in other European countries. In the European Region of WHO, vaccine uptake in older people ranged from 0.03% to 76.3% over seven seasons (2008/2009–2014/2015). The median was 34.4%. In 2014/2015, only Scotland reached the WHO and European Council goal with an uptake of 75%. Among countries providing data for seasons 2008/2009 and 2014/2015, over half reported a drop in vaccination coverage among older people.11 Among people with chronic diseases, coverage in the European Region ranged from 0.3% in Kyrgyzstan to 86.8% in Georgia in 2014/2015.11
From a historical perspective, vaccines have substantially reduced the burden for infectious disease (eg, polio, measles, mumps and rubella) or have been eradicated (small pox).12 Vaccine safety have always been a concern. For example, measles vaccine was falsely linked to autism in the 1990s, which led to a dramatically drop in vaccine coverage in the UK and other countries. Misleading information about the safety of vaccines might have increased the vaccine hesitancy and reduced the coverage of some vaccines.13
The decline in coverage and an increase in vaccine hesitancy is of general concern. In the last years, several countries of the WHO European Region including Switzerland, had large outbreaks of vaccine-preventable diseases, including measles, rubella and influenza. Switzerland and other countries identified steps to improve vaccination coverage for vaccine-preventable infectious diseases.14 15 The relationship between vaccination uptake, knowledge, attitudes and awareness is complex.16 Reasons for people not getting vaccinated against influenza include underestimation of disease severity, fear of side effects and the cost of vaccines.17–19 Often people are unaware that they should receive the vaccination.17 For the seasonal influenza, the varying efficiency ranging from 30% to 60% depending on the season could play a role in the reduced coverage over time.20 21 However, mathematical models of influenza and vaccination showed that the health burden associated with influenza is more sensitive to changes in vaccination coverage than to changes in vaccine efficacy.21 Of note, the coverage of measles vaccination increased to almost 90% in young adults in Switzerland, probably due to the campaigns and a national measles strategy.22 The experience with measles could serve as a model for public health actions influenza.
The advent of the novel COVID-19 SARS-CoV-2 has profoundly changed everyday life in Switzerland and elsewhere. It is unclear how the COVID-19 pandemic will affect attitudes toward vaccines. The director of the US Centers for Disease Control has warned that a possible second wave of COVID-19 could be worse than the first.23 This has already been seen in the ‘Spanish influenza’ pandemic of 1918/1919. The Spanish influenza affected Switzerland in two waves. The first one occurred in July 1918, the second, more severe one, in October–November 1918.24 However, even in the absence of a second wave, a resurgence of COVID-19 that coincides with the start of the influenza season could significantly stress healthcare systems. An effective and safe vaccine against COVID-19 is unlikely to become widely available in 2020. Therefore, low influenza vaccination rates at around half the 75% coverage recommended for high-risk groups constitute a hazard that merits prompt, focused attention by public health authorities.
A concerted effort to increase influenza vaccination coverage in 2020/2021, when the COVID-19 pandemic to continue to pose a threat to the public’s health, is urgently needed. Influenza vaccination prevents deaths, morbidity, hospital admissions and other adverse health outcomes, in target populations such as older people, chronically ill people,25–30 and also children31 and pregnant women.32 The continued promotion of infection control measures such as avoiding close contact with sick people, covering one’s nose and mouth while coughing or sneezing, social distancing and hand hygiene will contribute to reducing the spread of both influenza and COVID-19.3
Our study has several limitations. Influenza vaccination status is self-reported in the Swiss Health Survey, and the reliability of the data unclear. For example, vaccination coverage could be lower if social desirability bias led to an overestimation of uptake. Conversely, incomplete recall of vaccinations could bias coverage downwards. Individuals younger than 15 years are excluded from the survey, but coverage in this age group might be even lower than in the 15–19 years old. A strength of our analysis is the fact that the survey is a nationwide and representative, and repeated every 5 years using the same methodology. Also, the analyses were weighted and adjusted for a range of potential confounders, which did not substantially change the results.
In conclusion, we need to increase influenza vaccination uptake, particularly in the elderly and chronically ill, who are also the risk groups most heavily affected by COVID-19. These efforts should include classic information campaigns, but novel approaches using social media should also be considered.33 34 Recommendations by healthcare professionals are essential to improve influenza vaccination coverage, such as client reminder/recall and standing orders.35 The preparation of influenza season 2020/2021 must start now to address the double burden of COVID-19 and seasonal influenza.
Patient and public involvement
The Swiss Health Survey is a nationwide, representative survey that is repeated every 5 years using the same methodology. The survey is conducted by the SFSO on behalf of the Swiss Government. The content of the survey is based on a holistic and dynamic health framework and contains questions on essential topics for the public and politics. The wording of the questions is regularly harmonised with the statistical offices of other countries in Europe.
Acknowledgments
We thank the Swiss Federal Statistical Office for providing the data of the Swiss Health Survey 2007 to 2017, and the people who participated in the surveys.
References
Supplementary materials
Supplementary Data
This web only file has been produced by the BMJ Publishing Group from an electronic file supplied by the author(s) and has not been edited for content.
Footnotes
Twitter @eggersnsf
Contributors Conception and design: LF, MZ, ME. Data analysis: KZ, LF, CB, MZ. KZ, LF, ME wrote the first draft of the paper and revised it based on comments from all authors. All authors reviewed and approved the final version of the manuscript.
Funding There was no specific funding for this project. ME was supported by special project funding (grant 17481) from the Swiss National Science Foundation.
Competing interests None declared.
Patient consent for publication Not required.
Ethics approval Data were collected anonymised and ethical approval was not required but we obtained permission to analyse and publish the data through a contract with the SFSO (Ref. 624.110-1).
Provenance and peer review Not commissioned; externally peer reviewed.
Data availability statement Data may be obtained from a third party and are not publicly available. Data may be obtained upon request from the Swiss Federal Statistical Office (SFSO).
Supplemental material This content has been supplied by the author(s). It has not been vetted by BMJ Publishing Group Limited (BMJ) and may not have been peer-reviewed. Any opinions or recommendations discussed are solely those of the author(s) and are not endorsed by BMJ. BMJ disclaims all liability and responsibility arising from any reliance placed on the content. Where the content includes any translated material, BMJ does not warrant the accuracy and reliability of the translations (including but not limited to local regulations, clinical guidelines, terminology, drug names and drug dosages), and is not responsible for any error and/or omissions arising from translation and adaptation or otherwise.