The authors have declared that no competing interests exist.
Conceived and designed the experiments: SHG BCC. Performed the experiments: SHC YMK MJG SHG BCC. Analyzed the data: JYH BCC. Wrote the paper: JYH BCC.
This study was carried out to estimate the vaccination coverage, public perception, and preventive behaviors against pandemic influenza A (H1N1) and to understand the motivation and barriers to vaccination between high-risk and non–high-risk groups during the outbreak of pandemic influenza A (H1N1).
A cross-sectional nationwide telephone survey of 1,650 community-dwelling Korean adults aged 19 years and older was conducted in the later stage of the 2009–2010 pandemic influenza A (H1N1) outbreak. The questionnaire identified the demographics, vaccination status of participants and all household members, barriers to non-vaccination, perceived threat, and preventive behaviors. In Korea, the overall rate of pandemic influenza vaccination coverage in the surveyed population was 15.5%; vaccination coverage in the high-risk group and non–high-risk group was 47.3% and 8.0%, respectively. In the high-risk group, the most important triggering event for vaccination was receiving a notice from a public health organization. In the non–high-risk group, vaccination was more strongly influenced by previous experience with influenza or mass media campaigns. In both groups, the most common reasons for not receiving vaccination was that their health was sufficient to forgo the vaccination, and lack of time. There was no significant difference in how either group perceived the threat or adopted preventive behavior. The predictive factors for pandemic influenza vaccination were being elderly (age ≥65 years), prior seasonal influenza vaccination, and chronic medical disease.
With the exception of vaccination coverage, the preventive behaviors of the high-risk group were not different from those of the non–high-risk group during the 2009–2010 pandemic. For future pandemic preparedness planning, it is crucial to reinforce preventive behaviors to avoid illness before vaccination and to increase vaccination coverage in the high-risk group.
Pandemic influenza A (H1N1) arose in North America in April 2009 and subsequently spread worldwide. It caused at least 18,449 casualties in 214 countries by June 7, 2010
During the early phase of the pandemic, a higher mortality rate among young adults compared to that occurring during seasonal influenza was reported. By reporting this statistic widely, the mass media amplified the fear among the general population. The response from the public based on this inaccurate information led to a number of problems, such as a strong demand for unnecessary confirmation testing for pandemic influenza or reluctance to receive the vaccine
Those with risk factors such as underlying comorbidity or age exceeding 65 years tend to develop complications from influenza that lead to a high mortality rate
This study was conducted to understand the difference in vaccination coverage between high-risk and non–high-risk groups during the 2009–2010 pandemic influenza A (H1N1) in Korea and to analyze the factors influencing the vaccinated and non-vaccinated. In addition, we investigated whether there was a difference between the groups concerning public perception and preventive behavior.
This was a nationwide, population-based cross-sectional study. The target study population comprised non-institutionalized individuals aged 19 years or older living in South Korea. Using well-trained professional interviewers, the Hyundae Research Institute®, a professional research company, conducted a telephone survey of 1,650 Korean residents over 19 years of age on 16–26 February 2010. Proportional quota sampling was used to ensure that respondents were demographically representative of the general population, with quotas based on age and region.
Only one participant per household was asked to answer questions about his/her pandemic influenza A (H1N1) vaccination status and that of all family members, perceived threat and preventive behaviors, triggering events for the vaccinated, barriers to vaccination for the non-vaccinated, and sociodemographic factors.
Before the interview, the interviewer explained the purpose of the study to all the respondents and obtained verbal informed consent from the respondents who agreed to participate. The questionnaire contained 11 questions Data on demographics, including age, sex, education level, income level, chronic medical disease, and family members according to age group were obtained. Each interview was divided into 2 parts. The first solicited responses concerning the public perception of influenza and preventive behavior, and the second part sought responses concerning pandemic influenza vaccination. Questions in the first part included “How much of a health threat is posed by influenza infection?”, and “What were your preventive measures during the epidemic?” For the second part, the questions included “Did you and your family members receive vaccination against pandemic influenza A (H1N1)?”, “What made you get a vaccination?”, and specifically for the non-vaccinated respondents, “What was the reason for non-vaccination?”
In Korea, the priority groups for pandemic influenza vaccination include healthcare workers, children aged 7–18 years, children aged 6 months to 6 years, pregnant women, caregivers for infants aged <6 months, nursing home residents, military personnel, people aged 19–64 years with chronic medical disease, and elderly people aged ≥65 years. Of these groups, special onsite immunization teams visited the 7–18-year-old children at school. This group was involved in mass vaccination. Therefore, it was suspected that the vaccination coverage for this age group was higher compared to other groups who visited medical centers voluntarily. Considering the sample size, people with chronic medical disease and those aged ≥65 years were deemed the high-risk group within the priority groups. Chronic medical diseases included cardiovascular diseases such as congestive heart failure and myocardial infarction, lung disease such as asthma and chronic obstructive pulmonary disease, diabetes, malignancy, chronic liver disease, and rheumatologic diseases such as systemic lupus erythematosus and rheumatoid arthritis.
The response proportions and 95% confidence interval were estimated and compared with the χ2 test according to vaccination status and risk group. We used logistic regression analysis to investigate age, sex, education level, and monthly income as potential factors leading to the risk groups deciding to be vaccinated. The difference in the vaccination rates of the risk groups was calculated using the Cochran-Mantel-Haenszel test, controlled by several variables.
The study obtained ethics approval from the Institutional Review Board (IRB) of Korea University.
The IRB waived the requirement for written informed consent because the data were analyzed anonymously, but verbal consent was obtained from all respondents before the interview was started.
Overall, 1,875 potential respondents were contacted. Of these, 1,650 participated in the telephone survey. The mean age was 44.89±15.18 years and 817 subjects (49.5%) were male. Two hundred and nine subjects (12.7%) were aged ≥65 years and 172 subjects (10.4%) had one or more chronic medical diseases. In total, 313 subjects (19.0%) were classified as high risk, being affected by diabetes (n = 67, 4.1%), cardiovascular disease (n = 66, 4.0%), lung disease (n = 30, 1.8%), malignancy (n = 14, 0.8%), chronic liver disease (n = 12, 0.7%), and rheumatologic disease (n = 8, 0.5%).
The survey established that the pandemic influenza A (H1N1) vaccination coverage was 15.5% among adults aged ≥19 years and 58.4% among elderly people aged ≥65 years; in the high-risk group, vaccination coverage was 47.3% among people with chronic medical conditions and those aged ≥65 years (
Vaccinated (%) | Non-vaccinated (%) | Total (%) | ||
Total | 255 (15.5) | 1395 (84.5) | 1650 | |
Sex | 0.207 | |||
Male | 117 (14.3) | 700 (85.7) | 817 (49.5) | |
Female | 138 (16.6) | 695 (83.4) | 833 (50.5) | |
Age groups (years) | <0.001 | |||
19–29 | 22 (7.3) | 278 (92.7) | 300 (18.2) | |
30–39 | 30 (8.5) | 325 (91.5) | 355 (21.5) | |
40–49 | 33 (8.7) | 346 (91.3) | 379 (23.0) | |
50–59 | 26 (8.8) | 269 (91.2) | 295 (17.9) | |
60+ | 144 (44.9) | 177 (55.1) | 321 (19.4) | |
High-risk group | 148 (47.3) | 165 (52.7) | 313 (19.0) | |
Age ≥65 years | 122 (58.4) | 87 (41.6) | 209 (12.7) | <0.001 |
Underlying disease | 68 (39.5) | 104 (60.5) | 172 (10.4) | <0.001 |
Diabetes | 26 (38.8) | 41 (61.2) | 67 (4.1) | <0.001 |
Cardiovascular | 28 (42.4) | 38 (57.6) | 66 (4.0) | <0.001 |
Lung disease | 14 (46.7) | 16 (53.3) | 30 (1.8) | <0.001 |
Malignancy | 5 (35.7) | 9 (64.3) | 14 (0.8) | 0.035 |
Chronic liver diseases | 2 (16.7) | 10 (83.3) | 12 (0.7) | 0.908 |
Rheumatologic diseases | 3 (37.5) | 5 (62.5) | 8 (0.5) | 0.128 |
Education level |
<0.001 | |||
Elementary school | 74 (46.3) | 86 (53.7) | 160 (9.9) | |
Middle school | 27 (19.7) | 110 (80.3) | 137 (8.5) | |
High school | 64 (13.3) | 416 (86.7) | 480 (29.7) | |
≥ College/university graduate | 81 (9.6) | 760 (90.4) | 841 (51.9) | |
Monthly income |
<0.001 | |||
<1.99 | 114 (27.6) | 299 (72.4) | 413 (28.5) | |
2.00–3.99 | 62 (11.1) | 499 (88.9) | 561 (38.6) | |
4.00+ | 44 (9.2) | 434 (90.8) | 478 (32.9) | |
Seasonal vaccination in 2009–2010 season | 174 (34.3) | 333 (65.7) | 507 (30.7) | <0.001 |
χ2 test.
Fischer's exact test.
Thirty-two missing values were excluded from the analysis.
One hundred and ninety-eight missing values were excluded from the analysis.
Exchange rate based on two million Korean won to US $1,830 and four million Korean won to US $3,660.
Age groups (years) | Number of all household members | Number of vaccinated | Vaccination rate (%) | 95% CI | |
≤6 | 299 | 171 | 57.2 | 51.6, | 62.8 |
7–12 | 363 | 305 | 84.0 | 80.3, | 87.8 |
13–15 | 224 | 163 | 72.8 | 66.9, | 78.6 |
16–18 | 217 | 134 | 61.8 | 55.3, | 68.2 |
19–64 | 3,943 | 413 | 10.5 | 9.5, | 11.4 |
≥65 | 551 | 284 | 51.5 | 47.4, | 55.7 |
Total | 5,597 | 1,470 | 26.3 | 25.1, | 27.4 |
95%CI, 95% confidence interval.
The rate of vaccination coverage of the non–high-risk group was 8.0%, whereas that of the high-risk group was 47.3% (
High risk | Non–high risk | ||||
Total | Vaccination (%) | Total | Vaccination (%) | ||
Sex | <0.001 | ||||
Male | 151 | 72 (47.7) | 666 | 45 (6.8) | |
Female | 162 | 76 (46.9) | 671 | 62 (9.2) | |
Age (years) | <0.001 | ||||
≤59 | 82 | 12 (25.6) | 1,247 | 90 (7.2) | |
60+ | 231 | 127 (55.0) | 90 | 17 (18.9) | |
Education level |
<0.001 | ||||
Elementary school | 118 | 64 (54.2) | 42 | 10 (23.8) | |
Middle school | 53 | 20 (37.7) | 84 | 7 (8.3) | |
High school | 65 | 30 (46.2) | 415 | 43 (8.2) | |
≥College/university graduate | 74 | 28 (37.8) | 767 | 53 (6.9) | <0.001 |
Monthly income |
|||||
≤1.99 | 174 | 90 (51.7) | 239 | 24 (10.0) | |
2.00–3.99 | 60 | 19 (31.7) | 501 | 43 (8.6) | |
4.00+ | 45 | 17 (37.8) | 433 | 27 (6.2) | |
All | 313 | 148 (47.3) | 1337 | 107 (8.0) | <0.001 |
Cochrane-Mantel-Haenzel test.
Adjusted by age, sex, education level, and monthly income with logistic regression analysis.
Thirty-two missing values were excluded from the analysis.
One hundred and ninety-eight missing values were excluded from the analysis.
Exchange rate based on two million Korean won to US $1,830 and four million Korean won to US $3,660.
The triggering events between the high-risk and non–high-risk groups are compared in
Among the non-vaccinated, the reasons for not being vaccinated between the high-risk and non–high-risk groups are compared in
OR | 95% CI | ||
Female | 1.02 | 0.72–1.45 | 0.923 |
Age ≥65 years | 5.84 | 3.59–9.49 | <0.001 |
Underlying disease | 2.08 | 1.31–3.12 | 0.002 |
Education level | |||
Elementary school | 1.19 | 0.43–1.65 | 0.838 |
Middle school | 1.08 | 0.58–2.11 | 0.763 |
High school | 1.21 | 0.54–1.16 | 0.826 |
≥ College/university graduate | 1.00 | ||
Monthly income (million Korean won) |
|||
≤1.99 | 1.14 | 0.52–1.57 | 0.641 |
2.00–3.99 | 1.01 | 0.64–1.56 | 0.988 |
4.00+ | 1.00 | ||
Severity perception | |||
More serious than seasonal flu | 1.07 | 0.49–1.76 | 0.826 |
Similar to seasonal flu | 1.11 | 0.46–1.76 | 0.757 |
Less serious than seasonal flu | 1.00 | ||
Prior seasonal flu vaccination | 3.68 | 2.55–5.29 | <0.001 |
Exchange rate based on two million Korean won to US $1,830 and four million Korean won to US $3,660.
OR, odds ratio; 95% CI, 95% confidence interval.
In this study, the cross-sectional telephone survey conducted determined that self-reported pandemic influenza vaccination coverage in adults aged >19 years was 15.5%. The vaccination coverage of all respondents' household members across all age groups was 26.3%. This finding was consistent with the 26.1% recorded in the Korean Immunization Registry (KIR) study
In univariate analysis, age ≥60 years, chronic medical disease, low education, and low income were associated with a high tendency for vaccination. The findings are consistent with the results of a seasonal influenza vaccination study in Korea
In the high-risk group, the major triggering event for pandemic influenza vaccination was receiving a notice from a public health organization, rather than the more easily accessible mass media campaigns. The respondents' major reasons for pandemic influenza non-vaccination were “confidence in health” and “not enough time to get vaccinated.” These reasons for non-vaccination were consistent with a previous study carried out in Korea
More than half of the respondents perceived pandemic influenza as being more serious than seasonal influenza, and about 20% perceived pandemic influenza as a very severe disease. However, perception of the severity of pandemic influenza was not the influencing factor for vaccination uptake. This result was different from studies in the United Kingdom, Greece, and Australia, where a positive correlation was reported between perception of the severity of pandemic influenza and compliance with vaccination
As a response to the threat of pandemic influenza, more than 90% of people will adopt one or more preventive behaviors. However, apart from hand washing, less than 50% of the respondents practiced preventive behaviors such as avoiding crowded places or public transport. In addition, there was no significant difference in preventive behaviors between the high-risk and non–high-risk groups. Early use of a vaccine is not applicable during pandemic influenza, thus preventive behaviors are crucial to mitigate further spread of the infection. Therefore, efforts to enhance the knowledge of preventive behaviors could be the main strategy in preparing for future pandemic influenza.
This study had several limitations. First, the high-risk group consisted of the elderly (aged >65 years) and people with chronic medical conditions. Therefore, other priority groups such as pregnant women and healthcare workers were not included. Second, chronic medical conditions and vaccination status relied entirely on self-reporting. The vaccination rate was similar when compared with KIR data, but the rate was relatively overestimated in chronic medical conditions. Third, this was an observational study, which is inherently limited for explaining correlations.
Despite these limitations, this study does suggest that disseminating accurate information about influenza and the necessity of vaccination by the government or public health organizations appears to be a valuable component for those at high risk.
In summary, both perceived threat and preventive behaviors of the high risk group were not markedly different from those of the non-high risk group during the 2009 pandemic in Korea, except for vaccination coverage. Triggering events for vaccination was the major difference between high risk and non-high risk groups. Notice from public health organization was the most important event for triggering the decision to getting vaccination in those at high risk. It is also important to inform those at high risk to practice preventive behaviors to avoid getting ill before vaccination.
The authors would like to thank Hyundae Research Institute® for their assistance in implementing the survey.