Weakened immune system leaves elderly prone to the virus
At every stage and in every impacted nation, COVID-19 has struck the elderly hardest.
According to the Centers for Disease Control and Prevention, 8 out of every 10 COVID-19 deaths in the U.S. have occurred in adults age 65 and older. This age group also accounts for upward of 70 percent of all coronavirus hospitalizations nationwide.
Why? The prevalence of underlying health conditions like diabetes and heart disease as we grow older plays a big role. But experts at the Oklahoma Medical Research Foundation say there' s another culprit that bears part of the blame: our immune system, the biological network whose job is to protect us against foreign invaders like viruses.
“The general line of thinking is that immunity falters with normal aging, just like our muscle mass and cognitive function,” said Dr. Hal Scofield, a physician-scientist at OMRF. “You don't see pro athletes playing after age 50. We have a shelf life physically, and that goes for immunity, too.”
That waning immunity leaves older people more prone to serious complications not
only from COVID-19 but from seasonal illnesses like the flu.
T cells and B cells, special types of white blood cells involved in the immune response, offer clues to why immunity declines with age, according to OMRF immunologist Susan Kovats, Ph.D. “We don't know all the specifics behind the decline in immune function with aging, but we do know that both T cell and B cell function deteriorates with age,” she said.
T cells are made by a small organ in your chest called the thymus, “which slowly shrinks over time and is essentially gone in your adult years,” said Kovats.
Meanwhile, she said, “The ability of B cells to produce highly specific antibodies that inactivate viruses also decreases with age.” B cell numbers decline to a greater extent in elderly men, Kovats noted, “which may explain why they are more likely to die from severe COVID-19 disease.”
These age-related declines explain why, for example, a virus like shingles tends to emerge from a weakened immune system later in life.
“If you've had chickenpox, the shingles virus stays in your body forever,” said Scofield, who also serves as associate chief of staff for research at the Oklahoma City VA. “When you're young, your immune system keeps the virus in check. As you age, your body begins to lose its defenses and that increases your likelihood of getting shingles.”
Weakened immunity has also made the annual flu shot less effective in the elderly, with the CDC reporting that only 25 percent of people age 50 and older were protected during the 201819 flu season.
“The immune responses to vaccines are not as good overall in the elderly, and this is a legitimate concern as COVID-19 vaccines are hurried to the finish line,” said Kovats. “A lot of work is being done to try to understand why the immune response weakens, and significant effort has gone into changing how vaccines are made for this age group in order to solicit better immune responses.”
Researchers at OMRF and across the country are investigating the mysteries of aging, as well as the immune system, to better protect a population that now counts more than 50 million Americans over the age of 65.
“COVID-19 is unlike anything the body has ever seen before, and older people do not respond well to pathogens or viruses they've never been exposed to,” Scofield said. “This is going to be a challenge, but the more we learn about how the immune system works, the better we'll be at protecting our seniors in future outbreaks.”