In a new study from Yale, researchers found although breakthrough SARS-CoV-2 infections tend to be mild, more older adults have developed severe breakthrough cases during the delta variant phase of the pandemic.
The findings reveal the importance of booster vaccinations.
For the study, the team monitored the disease severity among patients who tested positive for SARS-CoV-2.
Between August and mid-October 2021, 371 admitted patients tested positive for SARS-CoV-2, among whom 82 patients (22%), who were fully vaccinated, were severely or critically ill with breakthrough COVID-19 infections.
This marks a big rise in severe breakthrough infections as a percent of a total number of patients hospitalized with COVID-19. The current study was conducted before the emergence of the SARS-CoV-2 omicron variant.
The researchers also compared vaccinated patients with severe breakthrough cases of COVID-19 to unvaccinated patients.
The patients with severe breakthrough cases tended to be older (their average age was 71.6 compared with 55.2 for unvaccinated patients with severe COVID-19 infections), and risk factors including underlying heart disease and type 2 diabetes were more prevalent among those who were vaccinated.
The vaccinated patients with severe COVID-19 infections had better clinical courses, including shorter hospitalization length, decreased use of advanced oxygen support, and tended to have lower mortality rates.
The team says even with the increasing number of fully vaccinated patients developing severe COVID-19 infections, their overall clinical outcomes were better than unvaccinated patients admitted during the same time period, highlighting the efficacy of the vaccines especially in the vulnerable population.
How long patients had been vaccinated also appeared to play a key role in the emergence of breakthrough infections.
There was a clear trend in increasing number of severe breakthrough cases the further out from the time of vaccination. This highlights the importance of booster doses, as the efficacy of the vaccines appear to wane over time.
The Centers for Disease Control and Prevention report that around 19% of fully vaccinated people in the United States have received a booster shot as of Nov. 28.
Over 42% of fully vaccinated people aged 65 or older have received a booster dose.
If you care about COVID, please read studies about many Americans take immune-weakening drugs that may reduce COVID vaccine effects, and findings of COVID-19 vaccines need to be shored up with a plant-based diet.
For more information about the pandemic, please see recent studies about No, COVID vaccines don’t stay in your body for years, and results showing that in people who had COVID-19, Pfizer vaccine may protect against new variants.
The study is published in The Lancet Microbe. One author of the study is Hyung Chun.
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