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State of the Flu in Pa., Nation

What to know about the flu vaccine match, increasing cases, and the rest of the season

March 14, 2022

The flu has outpaced last year’s historically mild season, but its spread remains below pre-pandemic years, state and federal figures indicate.

Earlier this year, public health officials urged caution about the potential for a “twindemic” of COVID-19 and the flu. While COVID-19 cases reached historic highs this winter due to the Omicron variant, the flu has remained below pre-pandemic levels.

It’s good news that the spread of the flu has been milder than previous years, but the season is not over. Flu activity in Pennsylvania and the United States is moderate and has increased slightly during the past four weeks, the Pennsylvania Department of Health notes.

Flu cases have increased during the past four weeks to more than 2,200 in Pennsylvania, but remain below the season’s late December highs of about 5,400. During the 2017–2018 flu season, the weekly case count peaked at more than 14,000, state figures show.

Recent public health reports indicate this year’s dominant strain appears to be different from the vaccine reference viruses, but the vaccine still offers protection against severe disease.

Research published in the Centers for Disease Control and Prevention (CDC) Morbidity and Mortality Weekly Report (MMWR) notes that “a growing body of evidence suggests that influenza vaccination can avert serious outcomes, including hospitalization, ICU admission, and death, among persons who are vaccinated but still become infected.”

Here are five things to know about this year’s flu season:

Comparing caseloads:  The fears of a COVID-19 ‘twindemic’ have not appeared to date. Flu levels are above last year’s total but below the four seasons preceding the COVID-19 pandemic. From October through March 5, there have been 40,484 flu cases in Pennsylvania

Vaccine mismatch:  The H3N2 virus has been the main circulating strain this year and the dominant strain appears to be “antigenically different from the vaccine reference viruses,” the CDC notes. Newly published research indicates this year’s vaccine prevented about 16 percent of mild cases, but offered some protection against more severe complications

Emergency visits:  In Pennsylvania, influenza-related illnesses accounted for more than 4 percent of emergency department visits during late December but less than 1 percent of visits during the week ending March 5

Recommendation:  The CDC recommends influenza vaccination for everyone 6 months and older as long as influenza viruses are circulating. This helps prevent complications from viruses that tend to appear later in the season, such as 2009 pandemic A (H1N1) and influenza B viruses

Quotable:  “Influenza activity is difficult to predict, and strategies to prevent influenza illness remain important to reduce strain on health care services,” according to the MMWR report on vaccine effectiveness

HAP will continue to monitor the ongoing flu season and provide updates to members and the general public. In addition, HAP joins public health advocates to encourage everyone who is eligible to get vaccinated against COVID-19 and the flu.

Getting vaccinated is one way to help limit the spread of infectious diseases to you, your loved ones, and your local community. For more information about flu season, contact Mary T. Catanzaro, RN BSMT (ASCP) CIC FAPIC, HAP’s infection preventionist.