University of Iowa-led study finds COVID vaccine ‘highly effective’ in health care workers

IOWA CITY — The Pfizer-BioNTech and Moderna vaccines have proved “highly effective at preventing symptomatic COVID-19” among health care workers in “real-world” settings, according to a new national study that involved over 300 University of Iowa Health Care workers.

The project, co-led by UI professors of emergency medicine Nick Mohr and David Talan, involved 4,931 health care workers from 33 medical centers — including UI Hospitals and Clinics — between December 2020 and May.

It aimed to take the research on the effectiveness of these “messenger RNA” types of vaccines beyond the clinical-trial setting into the “real world,” according to Mohr. The mRNA vaccines teach cells how to make a protein that triggers an immune response inside the body.

The project found the vaccines to be highly effective in the population on the front lines of America’s battle against the virus — including health care workers at greater risk of contracting severe COVID-19, and also those in racial or ethnic groups disproportionately affected by the pandemic.

Findings, published Sept. 22 in the New England Journal of Medicine, showed a two-dose regimen of the Pfizer vaccine to be 89 percent effective against symptomatic COVID-19 and the Moderna version to be 96 percent effective.

“Vaccine effectiveness was similar in subgroups defined according to age,” according to the study, “race and ethnic group, presence of underlying conditions, and level of patient contact.”

That means full vaccination — seven or more days after a second dose — was just as effective in health care workers over age 50; among ethnic groups hit harder by the pandemic; for those with underlying medical conditions; and for workers who interacted more with virus patients.

The study shed light on the benefit of partial vaccination — 14 days after a first dose through six days after the second dose — with a 78 percent-effective rate for the Pfizer vaccine and an 89 percent-effective rate for Moderna.

Vaccine effectiveness was lower among a combined group of partially and completely vaccinated immunocompromised workers — at 39 percent.

Due to the short study period, findings don’t answer the question of how long vaccines offer protection, according to UI Health Care. And, because data were collected before the delta variant emerged, “vaccine effectiveness may have changed compared to effectiveness against earlier variants.”

“We will continue to study how the vaccines perform as the pandemic continues to evolve,” Mohr said in a statement. “Keeping track of changes in vaccine effectiveness and duration of protection is critical to our ability to protect health care workers and keep our communities safer.”

Mohr and Talan — who has a dual appointment with UI Health Care and the David Geffen School of Medicine at the University of California-Los Angeles — led the entire Centers for Disease Control and Prevention-funded study.

The project enrolled 1,482 participants who had COVID-19 symptoms and tested positive, and 3,449 who had symptoms but tested negative.

“Among the enrolled health care personnel, 69 percent worked at acute care hospitals (including emergency departments), 31 percent in outpatient or specialty clinics, 1 percent in urgent care clinics, and 1 percent in long-term care facilities,” according to the study.

Although about 300 UIHC workers participated in the study, more than 15,500 UIHC employees have been fully vaccinated. Other breakout findings of the health care setting research include:

UIHC has been involved in numerous COVID-19-related research trials since the pandemic began, not just for vaccines and their effectiveness but for treatment methods and tools and now booster shots. UIHC currently is participating in effectiveness testing of Pfizer booster shots, and is involved in a trial for a new COVID-19 vaccine from the pharmaceutical company Sanofi.

In August 2020, more than 250 Iowans from across the state participated in UIHC’s portion of the Pfizer-vaccine trial, which would lead to the first COVID-19 vaccine to receive emergency approval by the Food and Drug Administration. Another 150 Iowans later stepped up to participate in UIHC’s portion of a trial for a Novavax COVID-19 vaccine, which could be granted emergency approval later this year.

UIHC is an attractive site for trials because Iowans have proved to be “reliable and dedicated research subjects that follow through on their commitments.”

“Participating in a vaccine clinical trial is a big commitment,” UI Carver College of Medicine Executive Dean and head of UI vaccine trials Patricia Winokur said in a statement. “Our Pfizer-BioNTech trial participants agreed to be followed for two years, filling out a diary once a week, and our Novavax trial participants even fill out daily diaries.

“Most of our participants have been very compliant throughout the duration of the study, which not only provides more complete data to assess safety and efficacy, but also leads to additional vaccine trial opportunities.”

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