Report from Vanderbilt University: With the emergence of the Delta variant this summer, hospitalizations and serious illness associated with COVID-19 have increased in Tennessee. On July 4, 2021, there were 213 hospitalized COVID-19 patients across the entire state. As of August 18, there were 2,497 hospitalized COVID-19 patients—a ten-fold increase in just over a month.
In addition to immunity gained through vaccination, there have been (as of Aug. 18) 963,647 documented COVID-19 cases in Tennessee. This total constitutes approximately 14% of the state population, though the official count understates the true total number of infections since not every positive case is detected and reported to the state.
Throughout the early summer, the combination of higher vaccination rates among the most vulnerable and “natural” immunity acquired through prior infection was offered by some as evidence the state could keep infections, hospitalizations, and deaths in check. However, the emergence of the Delta variant of the COVID-19 virus, coupled with a return towards normalcy in mobility and behavior, has resulted in a surge in infections and hospitalizations. Since mid-July, the rate of increase in COVID-19 hospitalizations has been higher than at any point in the pandemic.
As the Delta variant became entrenched in neighboring Missouri and Arkansas, growth in hospitalizations first began in the Memphis region but has since spread to every region of the state. Hospitalizations also have been concentrated primarily among the unvaccinated. Importantly, immunity acquired through prior infection provides some level of protection—though emerging scientific evidence suggests that unvaccinated individuals with prior COVID-19 are twice as likely to become infected by the Delta variant than those who have been vaccinated.
Facts About Natural Immunity and Vaccination
To determine if someone has antibodies that inactivate the COVID-19 virus in their blood, a special test is performed in a laboratory in which a sample of a person’s blood is combined with the virus and the amount of virus killed is measured.
When such studies are done on blood samples from patients who have recovered from COVID-19, the levels of these antibodies are not as high as they are in samples from patients who were vaccinated. In fact, some infected patients make very little antibody at all. Those patients who have been infected without symptoms or with only mild symptoms will generally have low levels of antibody and may not be protected from another infection. We do know, however, that if those patients are given even just one dose of vaccine, their bodies will make high levels of antibody that will inactivate the virus if they are exposed in the future.
In fact, it has been observed multiple times in several different scientific studies that the antibody levels after infection plus one dose of vaccine are often higher than levels after two doses of vaccine in individuals who have not been previously infected.
What does this tell us about immunity?
1. Individuals who have tested positive for COVID-19 infection often do not make adequate levels of antibody to protect them from another bout of COVID-19 infection.
2. People who have had previous infection need at least one dose of vaccine to raise antibody to protective levels.
3. Regardless of prior infection, full vaccination with one dose of the J&J vaccine or two doses of the Pfizer or Moderna vaccines is recommended for everyone age 12 and over.
4. Recommendations for additional vaccine doses (known as boosters) are emerging now.
Tennessee is now experiencing its highest growth in hospitalizations than at any point in the pandemic.
Moreover, as of this writing intensive care resource use for COVID-19 patients is at 91% of its previous peak. These trends suggest that if recent growth continues, Tennessee may soon eclipse high-water marks in ICU and ventilation use last seen in January.
Unlike early January 2021, safe and effective vaccines against COVID-19 are now widely available to the public that could stem the spread of the virus and the surge in hospitalizations that is now threatening the health of all Tennesseans due to staffing shortages, hospital diversions, and stretched resources. Especially when cast against a background of considerably higher vaccination rates among the oldest Tennesseans, the recent surge in hospitalizaitons underscores that severe COVID-19 can and does afflict anyone, including adults who may feel they are young and healthy enough to forego vaccination.
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