Calgary based study of influenza vaccination for young children: parental beliefs and behaviours

Canada Communicable Disease Report

1 July 2006

Volume 32
Number 13

Introduction

Influenza causes a substantial burden of illness for children and their families. This includes acute disease symptoms and complications, health care visits, the cost and provision of treatment, and absenteeism both of children from child care or school and parents from work(1-10). Influenza attack rates are highest among children(11), especially those who attend day care(9,12,13). The incidence of influenza varies from year to year(14). Recent surveillance studies have reported that, on average, 9% to 33% of children are affected per interpandemic season, the highest infection rates occurring in the first year of life(1,4,10,15-18).

Although the high incidence of childhood influenza infection is well recognized, there has been increased awareness in recent years about the severity of influenza infections in young children (19,20). Influenza is associated with considerable morbidity in children < 5 years of age, especially those with underlying illness (21), but even for those children who are otherwise healthy. These health concerns include lower respiratory tract disease, nonspecific febrile illness, secondary bacterial infections, and central nervous system complications(4,15,22,23) . In particular, healthy children < 2 years are at increased risk of hospitalization due to influenza-associated illness with hospitalization rates comparable to, and often exceeding, rates reported among adults ≥ 65 years of age(2,8,10,19,21,22,24-26). In addition, children are a major reservoir for the spread of influenza(4,6,11,15,17,19,27).

Vaccinating children against influenza both decreases morbidity in vaccine recipients and greatly reduces spread of the virus to others, as described in simulation models(17) and in real-life settings (9,17,27-30). Trivalent inactivated influenza vaccine is delivered as an intramuscular injection. The trivalent live attenuated influenza vaccine, currently licensed only in the United States for persons from 5 to 49 years of age, is delivered via intranasal spray(31).

In Canada, the National Advisory Committee on Immunization currently recommends that all children aged 6 to 23 months without contraindications should receive the safe(30,32,33) and efficacious (30,34) trivalent inactivated influenza vaccine annually(24) to prevent illness, reduce transmission, and reduce health care utilization (15,21,28,30,32,35,36). In addition, influenza vaccination is encouraged, but not formally recommended, for all persons > 2 years who wish to protect themselves against influenza. For the first time in 2004-2005, the provincial Department of Health in Alberta provided funding for universal influenza vaccine for all children 6 to 23 months of age. Vaccination was also provided to older children and adults with either high-risk health conditions or close contact with high-risk individuals. Although all other healthy children > 2 years were encouraged to obtain influenza vaccine, these children were not eligible for public funding, and their families were required to pay directly for the vaccine.

Although these recommendations are in place, parental acceptance strongly influences vaccine uptake(37). Relatively little is known about parental beliefs regarding childhood influenza vaccination in Canada(38-40). To achieve target level coverage of ≥ 90% of eligible recipients(24) it is essential that parental beliefs and behaviours about influenza vaccination of children < 5 years be explored in further depth.

This study sought to:

  1. measure community influenza vaccination rates of children attending community health centres (CHCs) for the 2004-2005 season in Calgary;

  2. describe common parental reasons for and against choosing childhood influenza vaccination;

  3. describe factors associated with vaccination against influenza; and

  4. make recommendations, if possible, about how to improve childhood influenza vaccination rates in future seasons.

Methods

The study design was a prospective cohort descriptive analytic survey. Data were collected in the autumn of 2004 using a brief self-completion questionnaire that was given to the mothers, fathers, or other caregivers of children (hereafter referred to as parents). This survey was a substudy of a larger ongoing study on the impact of routine pneumococcal conjugate vaccination on nasopharyngeal carriage of Streptococcus pneumoniae in young children(41). The study population consisted of the parent(s) of children aged 12 ± 2 months, 18 ± 2 months, and 4.5 ± 0.5 years who visited one of five participating CHCs in Calgary for routine immunizations or other community health visits. Potential parent and children participants were excluded if a language barrier existed between parents and study nurses or if someone other than a parent brought the child to the clinic and telephone consent could not be obtained from a legal guardian. The main study involved taking a nasopharyngeal swab of participating children, and potential participants were also excluded if they had known or suspected nasal abnormalities or bleeding anomalies, including children with frequent nosebleeds and those taking salicylate medication.

Written informed consent was obtained from the parents of all participating children. Parents completed a brief questionnaire with closed-ended and open-ended questions on the child's age, sex, and general health status; family composition; daytime care setting and playgroup attendance for the child; influenza vaccination status of both the child and all household members; and the parent's reasons for and against influenza vaccination of young children. Influenza vaccination status at the time of enrolment and by the end of the 2004-2005 influenza season was verified with the use of electronic records for all children. The Conjoint Health Research Ethics Board of the University of Calgary and the Calgary Health Region approved this study.

Data were entered into FileMaker Pro 7.0v3 (FileMaker, Inc., California, 2004), and parental responses to open-ended questions were classified into categories that were not mutually exclusive. Categorical data were analyzed using SPSS 11.0 for Mac OS X (SPSS Inc., Illinois, 2003). Comparisons between vaccinated and unvaccinated children were made using the Pearson chi-square test to explore factors associated with vaccination. For incomplete questionnaires, responses were excluded on a per question basis for missing information.

Results

Of 844 parents with age-appropriate children, 30 were excluded from participation. Of the remaining 814 parents, 577 agreed to enrolment in the study (70.9% participation rate). The characteristics of parents and children are shown in Table 1.

Table 1. Survey on influenza vaccination
in young children: characteristics of 577 parents
surveyed and their children

Characteristic Number (%)
Respondents
Mother

513 (88.9)

Father

61 (10.6)

Other caregiver

3 (0.5)

Children
Sex  
Female

259 (44.9)

Male

318 (55.1)

Age  
12 ± 2 months

239 (41.4)

18 ± 2 months

227 (39.3)

4.5 ± 0.5 years

111 (19.2)


During the 2004-2005 influenza season, 37.1% of children (n = 214) received the influenza vaccine, and 62.9% (n = 363) did not. Vaccination rates according to age category and eligibility for publicly funded influenza vaccine are shown in Table 2. Overall, 41.0% of children eligible for publicly funded influenza vaccine had been vaccinated either at the time of the study or by the end of the 2004-2005 influenza season. This contrasts with only 15.7% of children who were not eligible for publicly funded vaccine. For children who received influenza vaccine, parental responses about why the children were vaccinated are given in Table 3 and, for those who did not, the parental responses are given in Table 4.

Table 2. Vaccination of children against influenza (n = 577) according
to age and eligibility for vaccine funding

Children

Proportion vaccinated (%)*

All children

214/577 (37.1)

12 ± 2 months†

105/239 (43.9)

18 ± 2 months†

84/227 (37.0)

4.5 ± 0.5 years

25/111 (22.5)

Eligible‡

11/22 (50.0)

Non-eligible

14/89 (15.7)

All children 6-23 months†

189/466 (40.6)

All eligible children†,‡

200/488 (41.0)

* Vaccinated during the 2004-2005 influenza season before enrolment or subsequently.
† Alberta Department of Health provided public funding for annual influenza vaccine for all children aged 6 to 23 months.
‡ Eligible for publicly funded influenza vaccination because of diagnosed health issue or close contact with high-risk person. Of children aged 4.5 ± 0.5 years, those who were eligible for a publicly funded vaccine were more likely to be vaccinated than those who were not (p = 0.001).

Table 3. Parental responses (n = 214) about why their children
had received influenza vaccine

Parental/caregiver response Number (%)
Illness prevention of influenza and related complications 109 (50.9)
High risk due to age or increased exposure* 68 (31.8)
Protection of high-risk individual in close contact with the child 28 (13.1)
Positive recommendations† 24 (11.2)
High risk due to health issues‡ 17 (7.9)
Convenience, including timing and cost 7 (3.3)
Other positive reason 8 (3.7)
* Direct or indirect exposure
† By health care professional, media, or literature
‡ Either diagnosed or perceived health issues

Table 4. Parental responses (n = 363) about why their children had not
received influenza vaccine

Parental/caregiver response

Number (%)

Unnecessary*

133 (36.6)

Undecided or uninformed because of insufficient information

50 (13.8)

Safety concerns, including side effects, risks, or pain

47 (12.9)

Inconvenience, including timing and cost**

28 (7.7)

Efficacy concerns about protection offered by vaccine

16 (4.4)

Negative recommendations†

16 (4.4)

Preference to build natural immunity or use alternative means

16 (4.4)

No specific reason identified

15 (4.1)

Waiting‡

9 (2.5)

Other negative reason

27 (7.4)

* Child is healthy, low risk of direct or indirect exposure, limited previous influenza
experience, or low perception of influenza severity.
** If child is not eligible for free vaccination.
† By health care professionals, media, or literature
‡ For a scheduled appointment, an illness to pass, or other vaccinations to be up to date before influenza vaccine is given.

Comparisons were made between vaccinated and unvaccinated children to examine certain factors possibly associated with immunization (Table 5). Children from households in which one or more other members received influenza vaccine were more likely to be vaccinated than children from households in which no one else received influenza vaccine (69.1% vs. 23.2%, p < 0.001). Also, children with at least one parent aged ≥ 35 years were more likely to receive influenza vaccine than children with younger parents (63% vs. 50.9%, p = 0.01).

Table 5. Potential factors associated with children's receipt of influenza vaccine

Factor Proportion of children
vaccinated (%)
Proportion of children
unvaccinated (%)
p value
At least one other household member vaccinated against influenza* 143/207 (69.1) 83/357 (23.2) < 0.001
At least one other child lives in same household 131/213 (61.5) 234/360 (65.0) 0.4
At least one parent ≥ 35 years of age 126/200 (63.0) 176/346 (50.9) 0.01
Exposure to other children† 135/212 (63.7) 226/361 (62.6) 0.8
Health condition (diagnosed or perceived) 24/214 (11.2) 25/361 (6.9) 0.08
Child taking antibiotics currently or in previous 2 months 46/162 (28.4) 61/362 (16.9) 0.15
At least one ear infection in previous 12 months 59/212 (27.8) 89/360 (24.7) 0.41

* During the 2004-2005 influenza season.
† Through weekly playgroup, preschool, kindergarten, or childcare setting.

Discussion

In this study, during the first season of publicly funded influenza vaccine for children aged 6 to 23 months, 40.6% of children in this age group received influenza vaccine. This level of vaccination is far lower than the target level of 90%(24). However, such a level is perhaps not unexpected in the first year of implementation of a publicly funded program. Parents' awareness of the program is likely limited. This level of vaccination is similar to the 48% influenza vaccination coverage reported for the same age group in the United States in 2004-2005, which was also the first year that the Advisory Committee on Immunization Practices recommended routine influenza vaccination(42). Further promotion of the influenza vaccine for this age group is clearly needed.

Among parents who chose to vaccinate their child against influenza, the main reasons given for vaccination were illness prevention and increased risk because of age or exposure. It is encouraging that some parents are receiving accurate information and are choosing to vaccinate their child on the basis of valid reasons. It is of interest that only a minority of parents chose to vaccinate their child as a result of positive recommendations from a health care professional. Other studies have found that parents who discussed influenza vaccine with a physician were much more likely to vaccinate their child than those who did not(40,43). Therefore, health care professionals should be able to positively influence vaccination coverage by providing parents with increased information and recommendations for influenza vaccine.

Among parents who chose not to vaccinate their child against influenza, the most common reason given was that parents believed it to be unnecessary. Other studies have also found a lack of parental awareness that healthy young children, children with chronic health conditions, and children in close contact with high-risk individuals are all recommended to receive vaccination because of the increased risk and severity for either themselves or the high-risk individuals they come into contact with(22,39,40,43,44). Additionally, some parents chose not to vaccinate their child because they were undecided or felt uninformed about the vaccine. A lack of parental knowledge about vaccines has previously been documented(45). Together, these results suggest a need for increased parental education regarding influenza severity and vaccination for children. To be most effective, this education should include unbiased, readily available, easy-to-understand information that outlines the need for vaccination(4,44,46-48).

Safety concerns were important in some parents' decision not to vaccinate their child. Previous studies have determined that parental concerns about vaccine safety play an important role in the vaccination status of children(18,39,40,46,47,49). Increased awareness of influenza severity and vaccine safety may reassure parents with such concerns.

The children in this study were much more likely to have received influenza vaccine if at least one other household member had also been vaccinated. One previous study found a similar association(40). Presumably, if other household members have been vaccinated there is an increased understanding by parents about the value of influenza vaccine for children. Promoting influenza vaccination in the general public may improve vaccination rates for children as well as increase parents' awareness of the vaccine and its benefits for their families.

Children with older parents were also more likely to have received influenza vaccine. The reasons for this are not clear, but the finding may highlight the need to focus educational efforts on younger parents in particular.

In children 4 to 5 years old there was a striking difference in the level of vaccination between those children who were eligible for a publicly funded vaccine because of a health condition or close contact with a person at risk and those who were not eligible, with more than three-fold greater vaccine coverage in the group eligible for publicly funded vaccine. Although numerous factors may contribute to this difference, the absence of direct cost is likely a key one. In Canada, where all routine childhood vaccines are publicly funded with no direct costs to families, the uptake of vaccines that are available but not publicly funded is likely to be very low. In addition to being influenced by the burden of cost, parents may perceive that vaccines not publicly funded are unnecessary.

Finally, there was a near-significant association between influenza vaccination and a diagnosed or perceived health condition. The prevalence among the children of an underlying health condition was relatively small, and so the lack of significance may be largely a result of inadequate power. However, other studies have described higher vaccination rates among children with perceived or definite underlying health conditions(40,42,43). Health care professionals and information for parents should continue to promote vaccination for those with underlying disease or those in close contact with a high-risk individual.

Exposure to other children through weekly playgroups, preschool, kindergarten, or a child care setting was not associated with a higher level of vaccination. This finding is similar to that of a previous study(40). It is known that children who are exposed to numerous other children on a regular basis are at increased risk of infection, including influenza(9,12,13). Encouraging vaccination of these children should be made a priority.

Limitations

The study population consisted of parents and children visiting a CHC, nearly all for routine immunization visits. Thus, this sample is likely biased towards parents with positive beliefs about vaccination. Consequently, the level of influenza vaccination in this study may not be representative in general.

In addition, because we measured the overall level of influenza vaccination at the time of enrolment or subsequently during the 2004-2005 season, some parents may have been prompted to get their child vaccinated after participating in the survey, leading to an observation bias. However, only six participants subsequently had their child vaccinated who did not intend to do so at the time of enrolment, and therefore this bias appears to be negligible.

Conclusions

In conclusion, this study identified several important factors associated with influenza vaccination of young children. Increased parental education and positive recommendations by health care professionals should be encouraged, especially among young parents, to increase influenza vaccination rates to target levels. Promotion of the influenza vaccine among the general public may increase both vaccination rates in young children and awareness among parents of the vaccine and its benefits for their families.

Acknowledgements

Funding for this project was supplied by the Alberta Children's Hospital Foundation and an unrestricted research grant from Wyeth Canada. We would like to thank the CASPER research team: Stephanie Hui (study coordinator), Linda Hastie (study nurse coordinator), Janice Pitchko (research epidemiologist), and Freda Anderson, Loy Bacon, Sue Smylie, and Julie Zwicker (study nurses).

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Source : TD Chobotuk, BSc, medical student, University of Alberta, Edmonton, Alberta; JD Kellner, MD, Division of Infectious Diseases, Alberta Children's Hospital, Calgary, Alberta.

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