|Image of Hong Kong flu virus virions, the H3N2 subtype of the influenza A virus responsible for the flu pandemic of 1968-1969. (Credit: CDC/ Dr. Fred Murphy)|
The Oregon Immunization Program uses data from the ALERT Immunization Information System (IIS) to monitor the number of Oregonians receiving flu vaccinations throughout the 2013-14 influenza season. Snapshots of that information, updated weekly, are presented on this page.
Learn more about the ALERT IIS
Additional seasonal influenza surveillance updates
are available from the Oregon Public Health
Division’s Flu Bites
This is the final set of weekly charts for seasonal influenza immunizations in Oregon. As of Feb. 4th, the January surge in immunizations is over. From this point to the end of the influenza season only low levels of new immunizations are expected. To date over a million influenza immunizations have been reported to ALERT for this season. The total for both reported and non-reported influenza immunizations is expected to exceed 1.4 million.
Through the second week of January influenza immunizations strongly surged in Oregon. This surge may be a product of increased public awareness of influenza cases in their communities as well as from substantial news reports about the influenza season. While the January surge in influenza immunization appeared as a novel event in the 2012-2013 season, the current results make for two January surge years in a row. Perhaps a trend for late season immunization is developing. The surge includes some young children receiving their second dose for the season, but is also spread more broadly among young and middle-aged adults.
The second week of January also marks a milestone, as over one million influenza immunizations for Oregonians in the current season have been reported to ALERT. The current season is on track for a record number of influenza immunizations administered and reported to ALERT.
For the end of 2013, weekly influenza immunizations dropped across Oregon. However in January a strong surge in delivery appears to have developed. It is likely that increased community awareness and media reporting of influenza disease, hospitalization, and death are driving the current surge in January immunizations. In the last season, 2012-2013, a strong surge in immunization occurred in January that may have been related to media reports. However in 2011-2012 there was no January surge. For this week the charts of influenza immunizations have been extended out to March of 2014. Along with the comparison to the last season, (2012-2013), the season prior to that has also been added, (2011-2012). As a caveat, increases from 2011-2012 to the present represent both increased ALERT reporting by providers as well as increases in vaccination.
For the last week of 2013, influenza immunization totals continued to drop in Oregon. The open question going into January is whether increased community awareness and media reporting of influenza disease, hospitalization, and death will drive a surge in January immunizations. In the last season, 2012-2013, a strong surge in immunization occurred in January that may have been related to media reports. However in 2011-2012 there was no January surge. For this week the charts of influenza immunizations have been extended out to March of 2014, and along with the comparison to the last season, (2012-2013), the season prior to that, (2011-2012), has been added. As a caveat, increases from 2011-2012 to the present represent both increased ALERT reporting by providers as well as increases in vaccination.
As of week 51, (Dec. 15th to Dec. 21st) the total volume of influenza immunizations reported to ALERT remains at or above the levels observed in the 2012 to 2013 season. December immunizations remained steady through Dec. 21st. This is in contrast to the prior season, where a sharp peak and subsequent falloff occurred in December.
For this week we have included a chart of age groups by when they receive influenza immunizations. As December demand for immunization is steady, the question is who is getting immunized late in the immunization season. In past seasons, December and later immunizations have been skewed toward teens and younger adults. This season is following the same pattern, with teens and young adults twice as likely to get immunized in November or December than are seniors. A possible factor may be that influenza immunization for these younger groups is influenced by media accounts of flu and the presence of disease in local communities.
While there is typically a rebound in seasonal influenza immunization in mid-December, only a slight bump was observed this year. As of week 50, Dec 8th to Dec 14th, overall delivery of influenza immunizations appears to have turned downward again. While this suggests that the immunization season is largely winding down, it is still possible that a surge in demand could happen in January. On the state level, the Oregon Immunization Program is forecasting that 32% of Oregonians have received an influenza immunization to date for this season. This immunization rate is not uniform however across age groups or regions of the state. With the exception of Harney County, all of the southern counties in Oregon have rates at or below 25%. Other counties with rates at or below 25% include Clatsop, Umatilla, and Union Counties.
For the beginning of December immunizations have slightly rebounded from the Thanksgiving slump. As of week 49 (Dec. 1st to Dec 7th) immunization totals remain at or above last year’s totals, with over 800,000 influenza immunizations reported to ALERT. However the December surge that happened in the 2012-2013 season is not observable to date this year.
The map of projected influenza immunization rates across the state continues to show disparities between southern Oregon counties and the rest of state, with a few exceptions. As a caveat, for small counties it is difficult to assess whether low rates are due to lack of reporting or to lack of vaccination. However the broad swath of lower immunization rates across the southern counties may imply that a regional, rather than a local, problem exists with influenza immunization. An interesting feature in this map is the comparison of Linn & Benton Counties; while the two counties largely share health care systems, their populations are distinctly different with regard to influenza vaccination rates.
For the last week in November (week 48) we saw a steep drop in seasonal influenza immunization. This was expected, and a drop in immunizations around Thanksgiving is usual. During the 2012-13 influenza season, the rate of immunizations sharply picked up again in December and January, possibly spurred on by national and international news stories about influenza. Whether we see a strong increase again in December is difficult to predict at this time. To date, the level of immunization for seasonal influenza in Oregon remains at or above the levels observed last year.
The third chart included this week for immunizations illustrates how birth seasonality for children affects their rate of influenza vaccination. It is recommended that children have a yearly, routine visit to their provider. The yearly visit is a good opportunity to give immunizations, and for healthy children may be the only time they see their provider. Young children whose birthdays fall in the primary period for yearly influenza immunization have higher rates than those whose birthdays are outside of this period. That is, those with their second birthday between August and November are 1.56 times more likely to get an influenza immunization. This effect declines with age as the chart shows, and from age nine onward is small. It is possible that this decline with age reflects how children, after school entry, are no longer having yearly routine visits based on their age. Although it is not currently recommended, a routine Fall visit for all children would likely provide a boost to influenza immunization rates.
As of week 47 (Nov 17th to Nov 23rd) demand for seasonal influenza immunizations is declining but remains above last year’s levels. In past years immunizations have dropped off steeply before Thanksgiving. This year we have yet to see the steep holiday drop-off in immunizations, but that may come in the next week’s data. For this week we have included forecasts of comparative influenza immunization rates by age for the present season. For this season immunization rates among seniors appear high to date, though rates among young adults and teenagers are lagging. Older children and teenagers typically receive influenza immunizations when they visit providers for other reasons during the flu season.
As of week 46 (Nov 10th to 16th), the Oregon Immunization Program is forecasting that over 28% of Oregonians have received an influenza immunization for this season. Immunizations are more concentrated among older adults and children though, so there is still room to improve immunization rates among teens and adults. Going into Thanksgiving, immunization delivery typically drops then rebounds slightly in early December. A strong rebound for December and January immunizations occurred last year; whether such will happen again will not be clear for a few more weeks.