Advocating flu vaccination of healthcare workers to protect themselves and patients, a leading national epidemiologist says there is increasing evidence of post-influenza illnesses that can lead to heart attack, stroke, and permanent disability.

“The virus is even more nasty than you thought,” William Schaffner, MD, said Sept. 27 in Washington, DC, at a National Foundation for Infectious Diseases press conference on the upcoming influenza season. “Flu can predispose individuals to heart attack and stroke and can also initiate a slide into progressive disability.”

These events can occur even after one recovers from the acute respiratory illness. Indeed, influenza infection causes a systemic inflammatory reaction that can leave one vulnerable to several sequelae, said Schaffner, a professor of preventive medicine at the University of Vanderbilt Medical School in Nashville.

“This lingering inflammation can cause damage to the blood vessels, particularly those to the heart and the brain,” he said. “As a consequence, the accumulating evidence now shows that there is an increased risk of heart attack and stroke during the two to four weeks after recovery from acute influenza.”

Another post-flu event that is becoming clearer is that recovery from the initial infection may not be complete in the frail and elderly. Instead, flu can trigger a cascade into decline.

“They may never return to their pre-flu functional level,” he said. “Flu can knock down that first domino of progressive decline and progressive disability.”

While the seasonal vaccine efficacy is unpredictable year to year, it serves as an important safeguard to prevent pneumonia, hospitalization, and death.

“Vaccination also makes it less likely that you will spread the virus to others,” he said. “Nobody wants to be what I call the ‘dreaded spreader.’ Getting vaccinated is the socially responsible thing to do — while protecting yourself, you are also protecting those around you.”

The vanguard of these “communities of immunity” are healthcare workers, he emphasized.

“It is critically important that we lead by example by getting vaccinated to protect ourselves and our patients,” Schaffner said.

Vaccine Components Established

On the heels of a brutal 2017-2018 flu season, the vaccine strains for the 2018-2019 season have been set.1 The CDC and its advisors have determined the 2018-2019 U.S. trivalent influenza vaccines will include the following strains:

  • A/Michigan/45/2015 (H1N1)pdm09–like virus;
  • A/Singapore/INFIMH-16-0019/2016 (H3N2)-like virus;
  • B/Colorado/06/2017–like virus (Victoria lineage).1

“Quadrivalent influenza vaccines will contain these three viruses and an additional influenza B vaccine virus, a B/Phuket/3073/2013–like virus (Yamagata lineage),” the CDC stated.

The overall vaccine efficacy was estimated to be only 40% in the 2017-2018 season. The main problem was a mismatch between the circulating influenza A (H3N2) strain and the one in the vaccine. For H3N2, the vaccine was only 25% effective, but even that low efficacy reduces the chance of a person seeking medical treatment by one-fourth.

“The 2017-2018 influenza season was a high-severity season with high levels of outpatient clinic and emergency department visits for influenza-like illness (ILI), high influenza-related rates, and elevated and geographically widespread influenza activity for an extended period,” the CDC reported.2

Last season, flu illness ran high for a long time — from January 2018 through the end of March.

“ILI peaked at 7.5%, the highest percentage since the 2009 flu pandemic, which peaked at 7.7%,” the CDC concluded. “ILI was at or above the national baseline for 19 weeks, making the 2017-2018 season one of the longest in recent years.”

A record number of child deaths occurred in 2017-2018, totaling 180 children. Only 20% of them had been immunized, the CDC reported.

Live Mist Vaccine Back

The CDC recommends “routine annual influenza vaccination is for all people six months and older if they have no contraindications. Inactivated influenza vaccines (IIVs), recombinant influenza vaccine (RIV), and live attenuated influenza vaccine (LAIV) are expected to be available for the 2018–19 season.”

Also, recommendations regarding the use of LAIV4 have been revised, putting the mist vaccine popular with children back on the table under certain restrictions. Citing lack of efficacy, the CDC did not recommend the live vaccine last year or the prior season. The decision to recommend the vaccine came after the CDC’s Advisory Committee on Immunization Practices (ACIP) reviewed several sources of efficacy data.

While including the live attenuated vaccine as an option, ACIP said LAIV4 should not be administered “to children aged two through four years who have received a diagnosis of asthma or whose parents or caregivers report that a healthcare provider has told them during the preceding 12 months that their child had wheezing or asthma or whose medical record indicates a wheezing episode has occurred during the preceding 12 months.”

In addition, the live vaccine is contraindicated for those who are immunocompromised for any reason. “Close contacts and caregivers of severely immunosuppressed persons who require a protected environment” should not use LAIV4, either. Nor should pregnant women or people who have received antiviral medications within the prior 48 hours, the CDC recommends.


  1. Grohskopf LA, Sokolow LZ, Broder KR, et al. CDC. Prevention and Control of Seasonal Influenza with Vaccines: Recommendations of the Advisory Committee on Immunization Practices—United States, 2018–19 Influenza Season. MMWR 2018;67(3):1–20.
  2. CDC. Summary of the 2017-2018 Influenza Season. Aug. 31, 2018. Available at: