Severe Covid infections that aren’t defeated quickly can lead to long-lasting complications.
WSJ Opinion
The Biden administration’s plan to start rolling out Covid-19 booster shots next week has drawn criticism from some who claim there’s not enough evidence to show they’re needed. While breakthrough infections among the fully vaccinated have increased, most of those cases aren’t severe. The purpose of vaccines, say booster critics, is to prevent hospitalizations and deaths, not cold-like symptoms.
But many fully vaccinated people in recent months have reported getting severely sick with Covid, though not to the point of needing hospitalization. Boosters should help reduce the number of such cases. They could also prevent people from experiencing certain complications that sometimes follow a severe case of Covid.
Covid doesn’t merely infect the lungs and respiratory tract. It can attack other organs, including the brain, if it isn’t quickly defeated by your immune system. At the Alzheimer’s Association International Conference in July, researchers reported an uptick in inflammatory biomarkers indicative of Alzheimer’s disease and brain injury in the blood of patients who had been hospitalized with Covid.
One small study found that more than half of people hospitalized with Covid demonstrated cognitive decline two months after discharge. Short-term memory impairments, worse memory and cognitive test scores were associated with lower blood oxygen levels on a six-minute walk test, indicating a possible link to cardiovascular and pulmonary functions. Damage to the heart or lungs can reduce blood oxygen levels and result in the lingering “brain fog” that some Covid patients report months after their illness.
Another study in Lancet Psychiatry from May found that patients hospitalized with Covid were twice as likely to be diagnosed with dementia within six months than patients who weren’t.
Dr. Alireza Atri, director of Banner Sun Health Research Institute who specializes in cognitive disorders, says he’s been seeing many more patients in their 50s who have signs of early dementia after having Covid. “It’s a nasty neuro-destructive virus,” he says in an interview. “It can accelerate decline in people who are more susceptible to dementia and Alzheimer’s.”
One reason is the virus can attack the lining of blood vessels and cause small blood clots in the brain. It also uses the olfactory pathways to directly invade the brain, poking holes in the normally ironclad blood-brain barrier. The olfactory pathways project to parts of the brain that are very close to where new memories are formed, which is another reason that some Covid survivors may suffer from brain fog and loss of taste and smell.
The blood-brain barrier keeps out viruses and other harmful substances. If the brain’s protective armor is weakened, people may be susceptible to other invaders. People with the APOE4 gene allele, which has been connected to a higher risk of Alzheimer’s, may also be more vulnerable to Covid. A study last year found that the gene leads to blood-brain barrier dysfunction. Another study found that carrying two copies of the APOE4 gene allele (one from both the father and mother) made people twice as likely to develop severe illness.
People with less “cognitive reserve” are probably more vulnerable to Covid’s attacks on the brain, Dr. Atri adds. Cognitive reserve is the concept that individuals have different abilities to withstand neuropathological damage. Some people can still function normally despite damage to their brains since they can adapt—for instance, by rerouting processes. This is why many people with the hallmarks of Alzheimer’s in their brains don’t exhibit cognitive decline.
Higher education, social interaction and intellectually demanding jobs can increase mental resilience, though Dr. Atri worries that the virus may deplete the cognitive reserve. His goal isn’t to scare people from leaving their homes, but to create more public awareness so people can better assess their health risks and modify their behavior accordingly.
The growing evidence that a coronavirus infection that isn’t rapidly defeated by the immune system can seriously damage the brain and other organs argues in favor of expediting boosters, especially for older people who are at higher risk for both severe illness and dementia. Both the Pfizer and Moderna vaccines generate high levels of neutralizing antibodies, which are the immune system’s front-line defense. But these gradually wane over several months and are less effective against the Delta variant. A new study in the journal Nature indicates that vaccine antibodies are eight-times less sensitive to the Delta variant than to the Alpha.
While vaccines also generate back-up fighter T-cells, antibodies are still important because they give the immune system time to mobilize. The T-cell response in older people is generally more sluggish. Because the Delta replicates much faster than earlier variants, it can quickly overwhelm a sleepy or compromised immune system.
Boosters help because they provide a huge jolt of antibodies. In those age 65 to 85, a third dose of Pfizer’s vaccine has been found to produce a more-than 11-fold increase in antibodies compared with the second dose. A recent study from Israel found that people over 60 who received Pfizer boosters were more than 10 times less likely to get severe illness than those who had two shots.
So far there’s no evidence to suggest that side effects from a third dose are greater than those from a second. Covid will never be eradicated, and we’ll have to learn to live with it. That’s why we need boosters.
