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Oregon Seasonal Flu Vaccine Uptake

The Oregon Immunization Program (OIP) is using the ALERT Immunization Information System (ALERT IIS) to report on seasonal influenza uptake across the state. As a synopsis, ALERT IIS receives both child and adult immunization reports from the majority of Oregon healthcare providers and payors. Based on last year’s influenza season, OIP estimates that ALERT IIS is capturing 75% to 80% of all influenza immunizations given in Oregon. For near-real time tracking out of ALERT IIS, the data on immunizations are lagged by two weeks. Estimates made with two weeks of lag for reporting are generally good.

Learn more about the ALERT IIS


Additional seasonal influenza surveillance updates
are available from the Oregon Public Health Division’s Flu Bites report.


For the week ending on Dec. 6th, (epiweek 49), the number of influenza immunizations administered per week shows a small spike upward following Thanksgiving. The amount of further immunization to expect in December and January is difficult to predict at this point; the prior season upsurge in January may or may not occur this season. Overall, the total amount of influenza immunization in Oregon remains at or above prior season levels as of this date. For this week, the Oregon Immunization Program is presenting a map of estimated all-age influenza immunization rates by county. This map reflects immunizations given and reported through Dec. 6th, adjusted for expected reporting to the ALERT IIS. As in past influenza seasons, the map indicates a north-south divide in immunization rates by county. In general, Southern Oregon counties have the lowest influenza immunization rates (< 25%) along with some exceptions to the pattern in the northern half of the state. . As a caveat, it is difficult to separate a lack of reporting to ALERT IIS from a lack of influenza immunization in some counties. However, poor immunization reporting and poor immunization delivery, based on OIP’s experience, tend to go hand in hand.


For the week ending on Nov. 29th, (epiweek 48), the number of influenza immunizations administered continues to decline. This decline matches closely to the pattern from prior years. The total number of influenza immunizations given in the present season also continues to match or slightly exceed last year’s totals. As of Nov. 29th, the Oregon Immunization Program estimates that, overall, 33% of Oregonians have received an influenza immunization for this season. This is comparable to the rate observed last year at the same time: for the 2013-2014 season, the CDC estimated that as of Nov 30 th, 32% of Oregonians had received a seasonal influenza immunization. On a technical note, for the remainder of the current influenza season, OIP will be making forecasts based on a two week or shorter lag period in ALERT IIS reporting rather than a 3 week period.


As of Nov. 15th (epiweek 46), the weekly count of influenza immunizations given to Oregonians continues to closely match the last season’s counts. Earlier in the current season, we reported that 39% of adult influenza immunizations reported to the ALERT IIS came from pharmacies. As of the current date, 30% of all reported influenza immunizations and 38% of adult influenza immunizations were given at pharmacies. Generally, middle aged and senior adults make the most use of pharmacies for immunizations. The availability of influenza immunization at Oregon pharmacies is associated with higher local immunization rates, perhaps because pharmacies provide more vaccination opportunities with little waiting time. Teenagers also received influenza immunizations at pharmacies. However, the use of pharmacies for teenage immunization is presently limited by pharmacies’ inability to participate in programs such as Vaccines For Children (VFC) that provide free vaccine for children with financial barriers to immunization.


As of Nov. 8th, (epiweek 45), the weekly count of influenza immunizations given to Oregonians is continuing to decline. Going forward into the holiday season a drop in influenza immunizations is expected. Thanksgiving week, in particular, is usually low for immunization delivery, with a slight rebound expected in early December. From this point onward any substantial increases in weekly immunization delivery will likely be due to news reports of influenza or community awareness of local cases.

This week the Oregon Immunization Program is presenting a breakdown of influenza immunization reporting by age and gender. In the prior season (2013-2014), we found that gender parity for influenza immunizations existed for young children. Starting with teenagers the gender parity is skewed, with young women receiving substantially more influenza immunizations than men. At all adult ages, women are more likely to receive an influenza immunization than men. Results for the current season continue this pattern of gender disparity in immunization, with women receiving more influenza immunization than men.


As of Nov. 1st, the receipt of seasonal influenza immunizations per week among Oregonians is continuing to decline from a mid-October peak. Immunization receipt has remained strong, though, compared to prior seasons going into November. The total amount of influenza immunization for this season remains at or above the levels observed in prior seasons. This week’s reporting shows how the peak of immunization delivery for this season was spread out across several weeks, rather than as a single weekly peak as observed last year. Influenza immunization typically drops off going into Thanksgiving.

For the 2014-2015 influenza season, there are four major categories of influenza vaccine available for use. These types include a high-dose injectable formulation for seniors, a quadrivalent nasal spray for children, and both trivalent and quadrivalent injectable formulations for all ages. Quadrivalent vaccines, protecting against four strains as opposed to three, are new for this season. A limited supply of quadrivalent vaccine combined with higher cost and delays in shipping all potentially have limited its use for this season. In this week’s FluBites, the Oregon Immunization Program is including information on uptake for these four categories of vaccine by week. As of Nov. 14th, quadrivalent injectable vaccines accounted for 25.1% of reported doses in ALERT IIS; quadrivalent nasal sprays given to children accounted for 9.4% of reported doses; high-dose injectable given to seniors accounted for 11.4% of reported doses; and trivalent injectables accounted for 54.1% of reported doses. Strong differences in the use of quadrivalent vaccines were also observed across different regions of Oregon. The October surge in influenza immunizations up to the peak weeks was largely met by use of injectable trivalent vaccine.


Demand in mid to late October for influenza immunizations stayed at a higher than anticipated level according to ALERT IIS reporting. The peak of immunization receipt for influenza happened in week 42, rather than week 41 as initially reported. Usually influenza immunizations spike sharply in mid-October then decline quickly. However, this week’s c harts show that high levels of immunization were sustained for several weeks. As of Nov. 6th, influenza immunization levels are running at 5% higher than for the same period last year. According to the CDC, as of Nov. 5th over 1.2 million doses of influenza vaccine have been shipped to Oregon. To date, almost half of these have been used for Oregon residents and reported to the ALERT IIS.

For this week, the Oregon Immunization Program is presenting data on county influenza immunizations. Totals for each county as of Nov. 6th of 2014 are compared to the totals from the same period from last year’s reporting, as a measure of how counties are doing in comparison to the prior season. Last season’s final estimates of county influenza immunization rates are also included for reference. Several counties with low influenza immunization rates in the last season such as Curry and Lake Counties are showing substantial improvements in the current season. However, a number of counties are also showing declines in current season influenza immunizations reported to the ALERT IIS in comparison to last year at this time.


Through Oct. 24th, ALERT IIS has received over 430,000 reports of seasonal influenza immunizations for Oregon residents. The peak for influenza immunization occurred at this time during the 2013-2014 season. However, it is too soon to judge whether influenza immunizations have peaked for the present season. OIP estimates that over half a million Oregonians have received an influenza immunization so far this season. The total amount of influenza immunizations given up to Oct. 24th is close to the amount given at the same time last year.
Receiving a seasonal influenza immunization varies by age. Rates of immunization start high in early childhood, and decline from there into young adult ages. Adult influenza immunization rates increase moderately between ages 20 to 50 years, and then increase substantially after the age of 50. Overall, the receipt of influenza immunizations by age has not changed substantially between last season and the present season. Infant and senior adult influenza immunizations are slightly below last year’s amounts for this time of year. However, the effect of these declines is balanced in total by a slight increase in influenza immunizations for adults age 30 to 40 years.


Week 40: Through Oct. 4th, ALERT IIS already has over 200,000 reports of seasonal influenza immunizations for Oregon residents. OIP estimates that at least a quarter-million Oregonians have received an influenza immunization to date. Overall, the current influenza immunization season looks similar to last year’s season, but it is too early to forecast the whole season or when immunizations will peak. The majority of adult influenza immunizations (56%) so far were given in a medical setting such as a doctor’s office. However, pharmacists also account for a substantial amount (39%) of reported adult influenza immunizations. As of week 40, 61% of adult influenza immunizations have gone to women, as opposed to only 39% to men. This is the same as last season where adult women at all ages accounted for more reported immunizations than did men.


The final influenza vaccination uptake report for the 2013 - 2014 season is available. This report looks at uptake rates by demographic characteristics of the vacinees, geography and settings, and adult pharmacy usage.