Author: Rosenberg, Kenneth D
Date published: July 29, 2011
Starting with the 2010-11 influenza season, the Advisory Committee on Immunization Practices (ACIP) recommended that all children aged >6 months be vaccinated against influenza annually, and that previously unvaccinated children aged <8 years be given 2 doses of vaccine (1). The American Academy of Pediatrics (AAP) also recommends influenza vaccinations for this population (2). Throughout influenza seasons, preschool children often have higher rates of influenza-related hospitalization than any other age group except older adults (2-4). To estimate influenza vaccination coverage and identify sociodemographic and health-care usage correlates of influenza vaccination status among children aged 2 years, data from the 2006-2008 Oregon Pregnancy Risk Assessment Monitoring Survey follow-back survey (Oregon PRAMS-2) were analyzed. This report summarizes the results. In Oregon, 37.7% of mothers reported that their children had received an influenza vaccination during the most recent influenza season. Factors positively associated with recent influenza vaccination in the multivariable-adj usted model were children's influenza vaccination in the previous year, children's receipt of all recommended immunizations, children's uninterrupted health insurance coverage, and mothers' unmarried status. The only factor negatively associated with vaccination was use of a family doctor rather than a pediatrician for well-child visits. The concern about vaccinations most commonly identified by mothers of children who had not received an influenza vaccination during the most recent influenza season (33.9%) was the opinion that too many shots are given at a time. This report highlights the need for health-care provider- based and community-based strategies to increase influenza vaccination coverage for children in Oregon.
For this analysis, Oregon women with a live birth during 2004-2005 (Oregon PRAMS) were reinterviewed during 2006-2008 (Oregon PRAMS-2) shortly after the child's second birthday. PRAMS is a state-specific, population-based surveillance system that collects birth certificate- linked data from mothers with a recent live birth. Oregon PRAMS-2 is a follow-back survey for mothers who participated in the first PRAMS survey. Data for Oregon PRAMS and PRAMS-2 are collected via mailed surveys and by telephone surveys of persons who did not respond to the mailed survey. Data are weighted to adjust for the complex sampling strategy and nonresponse.
Oregon PRAMS-2 inquired about influenza vaccination coverage by asking the two-part question, "Has your 2-year-old ever had a flu vaccination or shot anytime during: a) This year's flu season (September thru March of this calendar year); b) Last year's flu season (September thru March of last calendar year)?" Recent receipt of influenza vaccine and receipt of influenza vaccination during the previous influenza season were dichotomized to "no" or "yes." The Cox proportional hazards model with constant follow-up time was used to calculate multivariable adjusted prevalence ratios (APRs) and 95% confidence intervals for vaccination coverage by selected sociodemographic and health-care characteristics using standard survey procedures (5,6).
The weighted response rate for PRAMS was 75.2% and for PRAMS-2 was 56.7% of the original PRAMS sampling frame. Of the 1,91 1 participants, responses were collected from 1,880 mothers of children alive at 2 years. The median age of children at the time of Oregon PRAMS-2 survey completion was 2. 1 years. A total of 1 97 surveys were excluded from the analysis because the influenza vaccination question was not answered. Another 157 surveys were excluded because of missing data for predictor variables, and, to limit conclusions to children of adult mothers, 37 surveys of mothers aged <18 years were excluded. The final multivariable model included 1,489 mothers.
In Oregon, 37.7% of the 1,489 mothers reported that their child had received an influenza vaccination during the most recent influenza season. Children with uninterrupted health insurance coverage had higher rates of vaccination (40.6%) compared with children whose coverage was interrupted (23.8%). Children with a regular health-care provider had higher rates of vaccination (38.6%) compared with children without a regular health-care provider (20.1%). Children who saw a pediatrician most of the time for well-child care visits had higher rates of vaccination (44.6%) compared with children who saw a family doctor (20.7%) and children who saw a physician assistant or nurse practitioner (21.7%). Children whose mothers reported that their child had an influenza vaccination during the previous influenza season had higher rates of recent vaccination (6 1 .8%) compared with children whose mothers did not report a previous influenza vaccination (15.5%). Children reported to have received all the recommended childhood vaccinations had higher rates of recent vaccination (40.5%) compared with children who did not have all vaccinations (7.2%) (Table 1).
The multivariable model included mother's age, race/ ethnicity, education, and marital status; the child's health insurance type; whether or not health insurance coverage was interrupted; whether or not the child had a regular healthcare provider; health-care provider type; receipt of previous influenza vaccination; and receipt of recommended childhood immunizations. Report of child's receipt of a previous influenza vaccination (APR = 3.3) and report of child's receipt of all childhood vaccinations (APR = 2.8) were positively associated with vaccination status. Children with uninterrupted health insurance coverage were more likely to be vaccinated than those with interrupted health insurance (APR = 1 .4). Children who saw a family doctor for well-child visits were significantly less likely to be vaccinated than those who saw a pediatrician (APR = 0.7). Children of unmarried mothers were more likely to be vaccinated than those of married mothers (APR = 1 .2) (Table 1).
Responding mothers were asked to select from a list of possible concerns they might have about vaccinations recommended for their child. Concerns identified by mothers whose children had not received a recent influenza vaccination included "Too many shots are given at a time" (33.9%), "Getting some of the childhood diseases is natural" (18.7%), "Some shots are given too early" (18.4%), and "Some shots do more harm than good" (15.3%) (Table 2).
Influenza vaccination of children remains a public health priority for at least three reasons. First, it is the best way to prevent influenza. Second, preschool children are at greater risk for influenza-related hospitalization than other populations (2-4). Third, preliminary studies suggest that vaccinating children against influenza might decrease transmission of influenza to adults and other children in the household (T). Nonetheless, fewer than two fifths of children aged 2 years received a recent influenza vaccination based on the 2006-2008 Oregon PRAMS-2 survey.
PRAMS-2 is a population-based sample and representative of children aged 2 years in Oregon. The PRAMS-2 vaccination coverage estimates exceeded estimates from the 2007 National Immunization Survey (NIS), which found that 24.5% of children aged <2 years received an influenza vaccination in Oregon (8). However, these results are less than the 2006-2007 and 2007-2008 estimates of 46.6% and 42.4%, respectively, for children aged <2 years from the Immunization Information System sentinel site in Oregon, which includes the greater Portland area (9). Differences in survey sampling methods are one potential reason for variation in these estimates. For example, Oregon PRAMS-2 vaccination coverage data were collected from mothers of children aged 2 years during 2006-2008, and the NIS data were collected from healthcare providers during the influenza season. Even so, the 24.5% vaccination coverage among preschool children in Oregon, based on NIS data, is below the national average of 31.8%.
The findings in this report are subject to at least three limitations. First, these findings were collected primarily through self-reported surveys of mothers and might be subject to recall and other response biases. Second, because the survey did not include a question regarding the number of doses of influenza vaccination that each child received, conclusions regarding full vaccination coverage cannot be made. Finally, the response rate for PRAMS was 75.2%, and, because of incomplete data, the analysis of PRAMS-2 responses included only 1,489 of the original 3,883 PRAMS respondents and might not be representative of all mothers of children aged 2 years.
The findings in this report are based on state data, which are useful for local action in Oregon. In light of the estimated influenza vaccine coverage of 37.7% in this study, the correlates of influenza vaccination identified, and the concerns about influenza vaccination expressed by mothers, two types of strategies are warranted to increase influenza vaccination coverage in this population. First, health-care provider- based strategies that assess and increase maternal knowledge regarding vaccination should be considered. Second, community-based strategies aimed at providing all children access to influenza vaccine and all other ACIP-recommended immunizations should be examined, including children eligible for free vaccinations through the Oregon Vaccines for Children Program (10). This especially might be necessary for children with interruptions in health insurance, those without a pediatrician as a regular health-care provider, and children of mothers with concerns about vaccinations.
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Kenneth D. Rosenberg, MD, Alfredo P Sandoval, MS, Oregon Public Health Div. Indu B. Ahluwalia, PhD, Charlan D. Kroelinger, PhD, Danielle T. Barradas, PhD, Div of Reproductive Health, National Center for Chronic Disease Prevention and Health Promotion; Timothy ]. Cunningham, ScD, EIS Officer, CDC Corresponding contributor: Timothy ]. Cunningham, tjcunningham @cdc.gov, 770-488-61 19.