How the Aging Immune System Makes Older People Vulnerable to Covid-19
A second wave
Several days after the innate immune response begins, the body begins a second wave of attacks against the viral invader. This adaptive immune system response is more targeted than the first, methodically destroying cells infected by this specific virus.
But in older bodies, the adaptive response not only takes longer to get into gear, it arrives to find a scene of inflammatory pandemonium, said Amber Mueller, a postdoctoral researcher at Harvard Medical School who co-authored a paper published in May about Covid-19 and aging. Think of firefighters coming to put out a house fire, she said.
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Frequently Asked Questions
Updated September 4, 2020
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What are the symptoms of coronavirus?
- In the beginning, the coronavirus seemed like it was primarily a respiratory illness — many patients had fever and chills, were weak and tired, and coughed a lot, though some people don’t show many symptoms at all. Those who seemed sickest had pneumonia or acute respiratory distress syndrome and received supplemental oxygen. By now, doctors have identified many more symptoms and syndromes. In April, the C.D.C. added to the list of early signs sore throat, fever, chills and muscle aches. Gastrointestinal upset, such as diarrhea and nausea, has also been observed. Another telltale sign of infection may be a sudden, profound diminution of one’s sense of smell and taste. Teenagers and young adults in some cases have developed painful red and purple lesions on their fingers and toes — nicknamed “Covid toe” — but few other serious symptoms.
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Why is it safer to spend time together outside?
- Outdoor gatherings lower risk because wind disperses viral droplets, and sunlight can kill some of the virus. Open spaces prevent the virus from building up in concentrated amounts and being inhaled, which can happen when infected people exhale in a confined space for long stretches of time, said Dr. Julian W. Tang, a virologist at the University of Leicester.
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Why does standing six feet away from others help?
- The coronavirus spreads primarily through droplets from your mouth and nose, especially when you cough or sneeze. The C.D.C., one of the organizations using that measure, bases its recommendation of six feet on the idea that most large droplets that people expel when they cough or sneeze will fall to the ground within six feet. But six feet has never been a magic number that guarantees complete protection. Sneezes, for instance, can launch droplets a lot farther than six feet, according to a recent study. It’s a rule of thumb: You should be safest standing six feet apart outside, especially when it’s windy. But keep a mask on at all times, even when you think you’re far enough apart.
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I have antibodies. Am I now immune?
- As of right now, that seems likely, for at least several months. There have been frightening accounts of people suffering what seems to be a second bout of Covid-19. But experts say these patients may have a drawn-out course of infection, with the virus taking a slow toll weeks to months after initial exposure. People infected with the coronavirus typically produce immune molecules called antibodies, which are protective proteins made in response to an infection. These antibodies may last in the body only two to three months, which may seem worrisome, but that’s perfectly normal after an acute infection subsides, said Dr. Michael Mina, an immunologist at Harvard University. It may be possible to get the coronavirus again, but it’s highly unlikely that it would be possible in a short window of time from initial infection or make people sicker the second time.
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What are my rights if I am worried about going back to work?
“You have a whole neighborhood of pedestrians or bystanders that are just hanging around, screaming their heads off, causing chaos,” she said. “To the point that it makes it harder for the firefighters to find the fire — to find the infection — and then put it out effectively.”
These delays mean that the pathogen has already made many copies of itself by the time the adaptive immune system gets to work and gains a foothold that might not have been available in a younger person. Additionally, older people have fewer fresh T cells, important players in the adaptive response that are trained to hunt down cells infected with a specific pathogen. When everything is working correctly, successful T cells make copies of themselves so that at the height of the infection, the body is swarming with them. Afterward, a few remain to prime us against return attacks from the same virus.
The supply of T cells that hasn’t already been assigned a pathogen dwindles over the decades. Those that remain may not be as good at copying themselves as the cells in younger people. And they may have trouble making the transition to patrolling the body against future attacks, said Dr. Shabnam Salimi, a professor of epidemiology and public health at the University of Maryland School of Medicine who wrote a recent paper about the interaction between aging and Covid-19.
“All these together make the immune system less functional during aging,” Dr. Salimi said.
Drug potential
Research investigating Covid-19 treatments will have to take into account the specific cells and substances that go awry when the immune system ages, and drugs under investigation for fighting aging may be useful against the coronavirus, write Dr. Salimi and her colleague John Hamlyn in their article.
So far, little has been straightforward when it comes to treatments for Covid-19. Since it became clear that the virus sometimes provokes an out-of-control immune response, researchers have been testing whether reducing inflammation might help. Drugs that tamp down the levels of cytokines, like those used for treating rheumatoid arthritis and other autoimmune diseases, have not shown success in fighting the virus. What’s more, chloroquine, which can help inhibit the aging of cells, caused increased mortality in Covid-19 clinical trials.
