Influenza and pneumococcal vaccination are important for preventing illness and the elderly with chronic diseases [7–9]. In a large sample of individuals with chronic diseases residing in Shanghai, China, we found low pneumococcal vaccination coverage over a 4-year study period and even lower influenza vaccine coverage. Uptake of both vaccines increased in those with more chronic diseases and with older age.
Chronic disease patients should be targeted for attaining high vaccination coverage compared to the remaining population. There are several overriding factors for exceptionally low coverage of pneumococcal and influenza vaccination among chronic disease patients in Shanghai community: (1) Studies have found that individuals lack awareness of pneumococcal and influenza vaccine [29, 30], and physicians do not often recommend vaccinations. (2) Vaccination for adults is not convenient. Community health care centers were responsible for implementing vaccinations in Shanghai. Most centers only provide 1 or 2 half days available for adult vaccination per week, while 6 half days are available for childhood vaccination. (3) Some adverse news related to vaccines have made people reduce their trust in vaccination programs [31, 32]. People with chronic disease and the elderly should have priority to take these vaccines due to their risk factors, but their chronic diseases may lead them to believe they have a higher risk for adverse reactions. (4) There is a limited supply of influenza vaccine. These reasons were not assessed in the current study, but could be explored in future research.
Pneumococcal vaccination coverage among adults 19-64 years at increased risk for pneumococcal disease was 24.0% in 2016 in the United States although it was much higher at 66.9% among adults over 65 years old . This is consistent with a study from Spain showing a higher proportion of adults over 65 years had received the pneumococcal vaccine (43.8%)  and demonstrating that vaccination levels in both young and elderly chronic disease patients in Shanghai are substantially lower than those found in the US or Spain. Because residents over 60 years of age in Shanghai are provided with free pneumococcal vaccination, the coverage in this age groups was not surprisingly higher than younger age groups and approaching that seen in those over 65 years in Hong Kong in 2015 (34%)  which also offers free pneumococcal vaccination to the elderly .
In our study, less than 1 percent of individuals received an influenza vaccine, which is far lower than in other countries, many of which provide free vaccine through government-sponsored or private insurance programs. Similar studies have shown higher influenza vaccination coverage in the United States (43.5%, among adults over 19 years, 2015/16 season) , UK (56.0%, chronic disease patients, 2007/08 season) , Poland (11.1%, chronic disease patients, 2007/08 season) , Korea (45.2%, over 40 years, 2012) , and Hong Kong (39%, over 65 years, 2015) . Our findings were relatively consistent with prior studies in China showing an average national vaccination coverage ranging between 1.5% and 2.2% in 2004 and 2014 . The coverage among patients over 60 years was significantly higher vs younger age groups below which was almost non-existent (i.e. close to 0%). One previous study found that elderly individuals who live with other family members are more likely to get vaccinated , perhaps as a result of other family members thinking the elderly, but not younger adults, need to get vaccinated or elderly individuals wanting to protect themselves against influenza as they care for their grandchildren.
We found that pneumococcal vaccination coverage was higher in rural areas which distinctly contrasted with influenza vaccination coverage which was lowest in rural areas. For influenza vaccination – which requires payment, individuals in urban area might be more able to afford the cost of influenza vaccine while patients in rural area might not . Higher pneumococcal vaccination coverage in rural areas may result from individuals trusting health care workers more .
The study showed that patients with multiple chronic diseases would be more likely to take pneumococcal vaccination than those with only one kind of chronic disease. This association could arise for several reasons. Individuals may perceive a greater personal risk of disease as they gain experience with more diseases. Or individuals with more co-morbid chronic diseases may have had more opportunities to get immunized through having more healthcare encounters.
The overall difference in uptake between influenza and pneumococcal vaccination could also be tied back to experiences and risk perceptions, as influenza could be seen as a nuisance disease that will quickly pass . The lack of funding to influenza vaccination from the government might be another important reason.
Pneumococcal vaccine uptake was a strong predictor of influenza vaccine uptake, which indicates that acceptance of one vaccine probably predicts for acceptable of others. Since the observation of pneumococcal vaccination was from January 2013 to July 2017 and the observation of influenza vaccination was only 2016/17 season, the impact of influenza vaccination on pneumonia vaccination could not be calculated for temporal reasons. Co-administration of both pneumococcal and influenza vaccines could reduce the incidence of various complications, hospitalization and mortality of chronic disease [8, 11, 12]. Only 0.3% of total sample had taken both pneumococcal and influenza vaccine in 2016/17 season, lower than that of hospitalized persons aged over 65 years in Victoria (46.6%) .
Our study looked at vaccination coverage for influenza and pneumococcal disease including predictors for vaccination among community members in Shanghai with chronic diseases. Interventions or policies like government funding as a potential strategy to encourage vaccination, especially influenza vaccination among chronic disease patients, should be implemented. Future studies should further examine differences in uptake of vaccines across different demographic groups.
Strengths and limitations
There are several strengths and limitations to this study. A strength of this study is the use of several comprehensive information systems as data sources, and the large number of individuals in the chronic disease management system. This system is opt-in for individuals with certain chronic diseases in the municipality, and an estimated 50% of individuals with chronic disease participate in it. It is possible that the individuals who participate in the chronic disease management system differ from those who do not. Non-participants, for example, likely have lower health-seeking behaviors and so our estimates of vaccination coverage may overestimate trends in the entire population of those with these chronic diseases. Future studies could evaluate why and how individuals participate in this database. In addition, limitations include a lack of information on key variables, like education and income. We only have data of pneumococcal vaccination coverage from 2013 onward and 1 season of influenza vaccination coverage, and inclusion of additional years would have permitted analysis of trends over time. The very low vaccination coverage, particularly for influenza vaccination, limits our ability to make recommendations beyond a general recommendation to increase coverage.