National study: Fully vaccinated adults less likely to be hospitalized

May 4, 2021
Larry Tremel, UCHealth's pharmacy director in southern Colorado, talks to Colorado Gov. Jared Polis as pharmacy techs prepare COVID-19 vaccinations.
Larry Tremel, UCHealth’s pharmacy director in southern Colorado, talks to Colorado Gov. Jared Polis while pharmacy techs prepare vaccine. Photo: UCHealth.

A national study shows that fully vaccinated adults 65 and older are 94% less likely to be hospitalized with COVID-19 than people the same age who were not vaccinated, according to an assessment by the Centers for Disease Control and Prevention.

UCHealth University of Colorado Hospital played a major role in the CDC study, helping with the design and conduct the study, a collaboration with two dozen hospitals and health systems across the United States on the effectiveness of Pfizer-BioNTech and Modern vaccines in preventing hospitalizations.

The results also showed that people 65 and older who were partially vaccinated were 64% less likely to be hospitalized with COVID-19 than people who had not received a vaccination. People are considered “fully vaccinated’’ two weeks after receiving their second dose of either the Pfizer or Moderna vaccines, both mRNA COVID-19 vaccines.

“This work confirms results from the vaccine clinical trials that vaccination is highly effective at preventing severe disease and hospitalizations for older adults,’’ said Dr. Adit Ginde, who led the research on behalf of University of Colorado Hospital, the only hospital in Colorado participating in the study. Ginde is Professor and Vice Chair for Research in the Department of Emergency Medicine and served as on the network steering committee and a co-author in the national, high-impact project.

“This is great news for public health and helps us return to normal life.’’ Ginde said.

The study represents only the beginning; collection of data on thousands of patients continues to further understanding of vaccine effectiveness, including for specific variants.

In recent weeks, Colorado hospitals have seen an increase in the number of people requiring hospitalization for treatment of COVID-19.

“At this point, nearly all of our hospitalized COVID patients have not yet been fully vaccinated,’’ Ginde said, adding that providers at UCHealth are seeing an increasing number of people who have received only one dose of the two-dose series for Pfizer and Moderna. “The second dose is critical to obtain the highest level of immunity. It’s not too late to receive the second dose, even if it is after the recommended 3-to 4-week time frame.’’

The CDC recommends everyone 16 years of age and older in the U.S. population get a COVID-19 vaccine as soon as possible. For more information about how to get a COVID-19 vaccine at UCHealth, click here.

“These findings are encouraging and welcome news for the two-thirds of people aged 65 and up who are already fully vaccinated,” CDC Director Rochelle P. Walensky said in a news release. “The results are promising for our communities and hospitals. As our vaccination efforts continue to expand, COVID-19 patients will not overwhelm health care systems – leaving hospital staff, beds, and services available for people who need them for other medical conditions.”

Photo of Dr. Andit Ginde
Dr. Adit Ginde

The assessment looked at hospitalizations in two U.S. hospital networks covering 24 hospitals in 14 states. Vaccine effectiveness was assessed by comparing the odds of COVID-19 vaccination among hospitalized people who tested positive for the virus that causes COVID-19 (these were case patients) versus those who tested negative (these were controls).

Among 417 participants in the assessment, there were 187 case patients and 230 controls. Close to half of the patients were 75 years or older.

Also noteworthy, while early reports from Israel also documented the real-world effectiveness of COVID-19 vaccination, including among older adults, those reports only looked at vaccination with the Pfizer-BioNTech vaccine. In this CDC assessment, both Pfizer-BioNTech and Moderna vaccine products were equally represented.

The assessment confirmed that vaccination provided no protection to people who had received their first dose fewer than two weeks earlier. It takes two weeks for the body to form an immune response after vaccination, according to the news release.

Two networks previously established to conduct surveillance for serious influenza disease provided the data for this assessment: Hospitalized Adult Influenza Vaccine Effectiveness Network (HAIVEN) and Influenza Vaccine Effectiveness in the Critically Ill (IVY). UCHealth participates in the IVY network.

This CDC will continue to assess the effectiveness of COVID-19 vaccines and results from assessments will help inform vaccine policy decisions aimed at saving lives and decreasing serious COVID-19 disease as much as possible. Ginde says, “This is particularly important with new variants emerging. We need to understand ongoing estimates of vaccine effectiveness as the virus changes.”

About the author

Erin Emery is editor of UCHealth Today, a hub for medical news, inspiring patient stories and tips for healthy living. Erin spent years as a reporter for The Denver Post, Colorado Springs Gazette and Colorado Springs Sun. She was part of a team of Denver Post reporters who won the 2000 Pulitzer Prize for breaking news reporting.

Erin joined UCHealth in 2008, and she is awed by the strength of patients and their stories.

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