By. Michelle Doebler, MPH, Influenza Epidemiologist, Michigan Department of Health and Human Services Division of Immunization
Each year influenza infections are estimated to cause millions of illnesses and thousands of hospitalizations and deaths nationally. The 2018-2019 flu season (September 30, 2018 – May 18, 2019) was moderately severe with two distinct waves of influenza activity corresponding to two different influenza A viruses circulating throughout the season. Influenza-like illness (ILI) activity began increasing in November 2018, peaked during mid-February 2019, and returned to below national baselines in mid-April 2019. Nationwide, the 2018-2019 flu season saw 21 weeks of elevated flu activity, making it the longest flu season in a decade.1 Flu activity in Michigan reflected the patterns of activity seen on a national level.
Preliminary estimates indicate that influenza burden from the 2018-2019 flu season was significant.2 Influenza infections caused approximately 42 million illnesses, up to 647,000 hospitalizations, and up to 61,000 deaths.2 Nationally, as of September 27, 2019, 135 influenza-associated pediatric deaths have been confirmed for the 2018-2019 flu season, and 3 of these deaths were from Michigan.3
The most effective way to prevent flu is with an annual influenza vaccination. The Advisory Committee on Immunization Practices recommends that all persons aged 6 months and older, without contraindications, receive an influenza vaccination every year. However, influenza vaccine coverage across the country is below the Healthy People 2020 goal of 70 percent. According to data from the Centers for Disease Control and Prevention (CDC), nationally only 49.2% of all persons aged 6 months and older received an influenza vaccination for the 2018-2019 flu season.4 The influenza vaccine coverage estimate in Michigan, utilizing data from the Michigan Care Improvement Registry (MCIR), for everyone aged 6 months and older was 30.4% for the 2018-19 season.
Influenza is not the “stomach flu” and not just a “bad cold” but rather is a highly contagious respiratory illness that can lead to extreme sickness and even death. Young children can be especially susceptible to severe complications from the flu. Children aged 6 months through 8 years may require two doses of influenza vaccine to be fully protected for a season. Last season according to MCIR data, Michigan’s flu vaccination coverage for children recommended to receive two doses was only 12.5%. Children that do not receive their second dose may still be at risk from developing illness from influenza infection. Providers are encouraged to communicate the importance of the second dose of influenza vaccine to parents. We need to do better in Michigan to protect our most vulnerable children.
Annually, CDC and the Michigan Department of Health and Human Services encourages providers to utilize the plethora of resources available to educate patients and increase influenza vaccine coverage rates. Many of these resources provide sample messaging to address the misconceptions preventing people from choosing to get an influenza vaccine. Educational materials are available at www.cdc.gov/flu and www.michigan.gov/flu.
To address vaccine effectiveness concerns, the World Health Organization reviews surveillance, laboratory, and clinical study data every year to make recommendations on the composition of the influenza vaccine.5 The Northern Hemisphere’s 2019-2020 flu vaccine composition includes an A/Brisbane/02/2018 (H1N1)pdm09–like virus, an A/Kansas/14/2017 (H3N2)–like virus, and a B/Colorado/06/2017–like virus (Victoria lineage). Quadrivalent vaccines include these three strains plus a B/Phuket/3073/2013–like virus (Yamagata lineage) virus.1
While influenza viruses are detected year-round in the United States, typically influenza infections are most common in the fall and winter months, with activity peaking between December and February.6 National Influenza Vaccination Week (December 2-8, 2019) highlights the importance of continuing flu vaccination through the holiday season and beyond. Providers are encouraged to assess their patients through the winter for flu vaccination status and continue to offer flu vaccine for the entire season!
1Xu X, Blanton L, Elal AI, et al. (2019). Update: Influenza Activity in the United States During the 2018–19 Season and Composition of the 2019–20 Influenza Vaccine. MMWR Morb Mortal Wkly Rep 2019;68:544–551. DOI: http://dx.doi.org/10.15585/mmwr.mm6824a3
2Centers for Disease Control and Prevention (CDC). (2019). 2018-2019 U.S. Flu Season: Preliminary Burden Estimates. Retrieved from https://www.cdc.gov/flu/about/burden/preliminary-in-season-estimates.htm
3CDC. (2019). Weekly U.S Influenza Surveillance Report. Retrieved from https://www.cdc.gov/flu/weekly/index.htm#ILIMap
4CDC. (2019). FluVaxView, 2018-2019 Flu Season. Retrieved from https://www.cdc.gov/flu/fluvaxview/1819season.htm
5CDC. (2018). Selecting Viruses for the Seasonal Influenza Vaccine. Retrieved from https://www.cdc.gov/flu/prevent/vaccine-selection.htm
6CDC. (2018). The Flu Season. Retrieved from https://www.cdc.gov/flu/about/season/flu-season.htm