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Tuesday, March 30, 2021

Two studies show how good vaccine decisions lessened impact of pandemic

Flu shots helped make flu season disappear, prioritizing front-line health care workers keep them on the job

By Will Collette

Two reports issued on the same day highlight the rewards for the community from good vaccine decisions.

Both report summaries appear below.

The first report says that people who got this year’s flu vaccine (as Cathy and I did), not only didn’t get the flu but faced lower risk from COVID. Getting vaccinated for flu did lower our risk of contracting COVID and, according to the data, people who had gotten flu shots had generally milder cases.

The second report discusses the positive effect on the battle against COVID that was gained by giving front-line health care workers top priority to get vaccinated against COVID when the first vaccines were approved. It immediately reduced the number of positive cases and may have saved our health care system from collapsing during the winter COVID surge.

Both studies underscore the value of getting vaccinated, not just for yourself, but for your whole community.

Here are the two reports:

Flu shot associated with fewer, less severe COVID cases, study finds

Michigan Medicine - University of Michigan

People who received a flu shot last flu season were significantly less likely to test positive for a COVID-19 infection when the pandemic hit, according to a new study. And those who did test positive for COVID-19 had fewer complications if they received their flu shot.

These new findings mean senior author Marion Hofmann Bowman, M.D., is continuing to recommend the flu shot to her patients even as the flu season may be winding down.

"It's particularly relevant for vaccine hesitance, and maybe taking the flu shot this year can ease some angst about the new COVID-19 vaccine," says Hofmann, an associate professor of internal medicine and a cardiologist at the Michigan Medicine Frankel Cardiovascular Center. Michigan Medicine is the academic medical center of the University of Michigan.

Researchers reviewed medical charts for more than 27,000 patients who were tested for a COVID-19 infection at Michigan Medicine between March and mid-July of 2020. Of the nearly 13,000 who got a flu shot in the previous year, 4% tested positive for COVID-19. 

Of the 14,000 who hadn't gotten a flu shot, nearly 5% tested positive for COVID-19. The association remained significant after controlling for other variables including ethnicity, race, gender, age, BMI, smoking status and many comorbid conditions, Hofmann says.

People who received their flu shot were also significantly less likely to require hospitalization, although the researchers didn't find a significant difference in mortality between the two groups. No one in the study tested positive for both infections at the same time.

The underlying mechanism behind the association isn't yet clear, Hofmann says.

"It is possible that patients who receive their flu vaccine are also people who are practicing more social distancing and following CDC guidelines. However, it is also plausible that there could be a direct biological effect of the flu vaccine on the immune system relevant for the fight against SARS-CoV-2 virus," she says.

Prospective longitudinal studies to examine the effect of the flu vaccine on respiratory illness are ongoing, including the Household Influenza Vaccine Evaluation (HIVE) study through the University of Michigan's School of Public Health.

"It's powerful to give providers another tool to encourage their patients to take advantage of available, effective, safe immunizations," says co-first author Carmel Ashur, M.D., M.S., an assistant professor of internal medicine and a hospitalist at Michigan Medicine.

Months ago, Hofmann was concerned about misinformation she kept seeing online that connected the flu vaccine with a COVID-19 infection. Prominent media outlets like Reuters debunked this theory, and she knew her team's data could also help address vaccine hesitancy.

"Instead of a concerning connection between COVID-19 and the flu shot, our publication provides more confidence that getting your flu shot is associated with staying out of the hospital for COVID-19," she says.

Before the pandemic hit, Hofmann and co-first author Anna Conlon, Ph.D., a U-M Medical School student, educated Frankel CVC patients about another encouraging association with the flu vaccine: cardiovascular protective effects.

"There's robust data that the flu shot prevents heart attack and hospitalizations for heart failure, which is an additional reason to get your vaccine every flu season," Conlon says.

Benefit of early vaccination on health care workforce

UT Southwestern Medical Center

Vaccinating health care workers resulted in an immediate and notable reduction of positive COVID-19 cases among employees, reducing the number of required isolations and quarantines by more than 90 percent, according to data at UT Southwestern Medical Center published in the New England Journal of Medicine.

Health care workers were among the first groups to be eligible for vaccination.

"Real-world experience with SARS-CoV-2 vaccination at UT Southwestern demonstrated a marked reduction in the incidence of infections among our employees, preserving the workforce when it was most needed," notes Daniel K. Podolsky, M.D., president of UT Southwestern and senior author.

During the first 31 days of vaccinations becoming available, UT Southwestern provided a first dose to 59 percent of roughly 23,000 employees, while 30 percent were able to be fully vaccinated in that time frame. Among the findings:

  • 1.5 percent became infected.
  • Infection rates were highest -- 2.6 percent -- among nonvaccinated employees.
  • Infection rates were lowest -- .05 percent -- among those fully vaccinated.

"Our ability to quickly vaccinate a majority of our workforce in the midst of what became the largest surge to date in the region made a critical difference in ensuring we were able to continue providing top-flight care while health systems were strained," says John Warner, M.D., executive vice president for health system affairs at UT Southwestern.

Researchers also saw advantages among partially vaccinated individuals, and from Jan. 9, the actual number of positive tests among all UT Southwestern employees was consistently lower than the number projected.

The data also show continued need to address vaccine hesitancy, with UT Southwestern now approaching 70 percent immunization among its workforce.

"In light of this real-world experience clearly demonstrating the effectiveness of immunization, further understanding of the reticence of some individuals to take advantage of vaccination bears even greater importance," says first author William Daniel, M.D., vice president and chief quality officer at UT Southwestern.

UT Southwestern has provided educational outreach to community groups and businesses, developed extensive online resources including Q&As and blogs, and is preparing to launch a multilingual public service announcement campaign to help educate diverse communities about vaccination and address issues of hesitancy.

"It is important to reach out across multiple platforms to effectively address people's questions so that we can continue to make progress on vaccine hesitancy," says Marc Nivet, Ed.D., executive vice president for institutional advancement at UT Southwestern.

Dr. Daniel, professor of internal medicine, holds the William T. Solomon Professorship in Clinical Quality Improvement at UT Southwestern Medical Center. Dr. Nivet is associate professor of family and community medicine. Dr. Podolsky, professor of internal medicine, holds the Philip O'Bryan Montgomery, Jr., M.D. Distinguished Presidential Chair in Academic Administration and the Doris and Bryan Wildenthal Distinguished Chair in Medical Science. Dr. Warner, professor of internal medicine, holds the Nancy and Jeremy Halbreich, Susan and Theodore Strauss Professorship in Cardiology and the Jim and Norma Smith Distinguished Chair for Interventional Cardiology.