Indianapolis, IN—Misinformation about and backlash against COVID-19 vaccines continues unabated. One recent talking point for those opposed to the vaccines is that breakthrough cases occur, so getting a shot is not effective.

A new study offers a strong argument to combat that position. It found that vaccine recipients who get infected with COVID-19 and are hospitalized are less likely to require intensive care, more likely to have a shorter hospital stay, and are less likely to die in the hospital than those who were not vaccinated.

The study from the CDC’s VISION Network provides evidence that while vaccination is not 100% effective in preventing infection, it has reduced disease severity during the periods of Delta and Omicron dominance.

The findings include:

• Time from hospital admission to discharge was 15% to 20% shorter for vaccinated patients compared with unvaccinated patients
• During the period of Delta predominance, vaccinated patients were half as likely as unvaccinated patients to be admitted to the ICU during their hospital stay. During Omicron predominance, vaccinated patients were 30% less likely than unvaccinated patients to be admitted to the ICU
• Slightly more than 10% of those hospitalized for COVID-19 died while in the hospital, with almost 81% of the deceased having been unvaccinated.

“This is one of the first studies to compare vaccine status of adults who were so sick with COVID that they were hospitalized,” stated study coauthor Brian Dixon, PhD, MPA, of the Regenstrief Institute and Indiana University Richard M. Fairbanks School of Public Health, both in Indianapolis. “The bottom line is that even with breakthrough cases—disease occurring in spite of vaccination—you were better off having been vaccinated and boosted as vaccine effectiveness waned, than not. The hospital course of stay was less severe, and you are less likely to go to the ICU and less likely to die.”

The study confirmed that vaccine effectiveness against severe COVID-19 requiring hospitalization declined less than vaccine effectiveness against infection only. Other VISION Network studies have demonstrated that booster shots can restore effectiveness.

The researchers assessed COVID-19 vaccination effect on illness severity among 27,149 adults hospitalized with COVID-19 from August 2021 to March 2022. The differences were evaluated in ICU admission, in-hospital death, and length of stay among vaccinated (two or three mRNA vaccine doses) versus unvaccinated patients. Participants were all hospitalized for more than 24 hours with COVID-19-like illness and positive SARS-CoV-2 molecular testing.

“During both Delta and Omicron-predominant periods, protection against ICU admission was strongest among three-dose vaccinees compared with unvaccinated patients (Delta OR [CI]: 0.52 [0.28-0.96]); Omicron OR [CI]: 0.69 [0.54-0.87]),” the authors advised. “During both periods, risk of in-hospital death was lower among vaccinated compared with unvaccinated but ORs were overlapping; during Omicron, lowest among three-dose vaccinees (OR [CI]: 0.39 [0.28-0.54]).”

Breakthrough COVID cases admitted to a hospital tended to be in older individuals and those with additional medical conditions, according to the report. It added that unvaccinated patients in the study were generally younger and healthier, with a lower percentage having any underlying medical conditions such as cardiovascular disease or diabetes, but a higher percentage having underlying respiratory conditions.

“We know that certain racial and ethnic groups, younger adults, those living in rural areas, those with low socioeconomic status, and uninsured persons in the U.S. tend to be less likely to be vaccinated,” stated study coauthor Shaun Grannis, MD, MS, of the Regenstrief Institute and Indiana University School of Medicine. “Hopefully this study will encourage those who have been hesitant to get vaccinated and boosted to reduce their risk of severe disease and death. Vaccination benefits individuals, families, communities, and the healthcare system.”

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