Coronavirus Briefing: Good News on Immunity
4 min read
We start today with some good news about immunity.
According to a flurry of new studies, it looks as if Covid boosters will continue to protect most people from serious illness and death for many months, and perhaps even years — which means we probably won’t need to line up for another shot anytime soon.
Previous studies have showed that antibodies, the body’s first line of defense against the virus, can wane over time, leading some to worry that we may be stuck in an indefinite cycle of boosters. But my colleague Apoorva Mandavilli said that antibodies were just part of the picture.
“People are obsessed with antibodies,” Apoorva said, in part because antibodies are relatively easy and fast to study. “But antibody levels always go down, and that does not necessarily mean that immunity to severe illness is waning. That’s a bad way to think about your immune system.”
Instead, the new research looked at other parts of the immune system that can remember and destroy the virus, including B cells and T cells. The studies found that this diverse repertoire of defenses should be able to protect people who have had three shots, or even two, for months or years.
“Think of antibodies like the frontline soldiers, the very first ones that are standing guard at the gates and preventing enemies from getting in,” Apoorva said. Over time, if your body doesn’t see any new enemies, there may be fewer of these guards at the gate.
“But let’s say that you have very few antibodies and the virus does get in, then you have these backup defenses,” Apoorva said. “The B cells make more antibodies and the T cells can destroy any cell that is infected, so between them, they can basically put a stop to the infection and stop you from getting sick.”
This dual punch of T and B cells helps explain why many people who received two or even three doses of the vaccine could still be infected with the Omicron variant but only a small percentage became seriously ill. And two of the recent studies show that a third mRNA shot produces a wider variety of antibodies and a richer pool of B cells, explaining why the boosted see better results.
The T cells produced by four Covid vaccines — Pfizer, Moderna, Johnson & Johnson and Novavax — are about 80 percent as powerful against Omicron as they are against other variants, according to the new research. Given how different Omicron’s mutations are from previous variants, it’s very likely that T cells would mount a similarly robust attack on any future variant as well, researchers said.
This matches what scientists have found for the SARS coronavirus, which killed nearly 800 people in a 2003 epidemic in Asia. In people exposed to that virus, T cells have lasted more than 17 years. So far, experts said, the evidence indicates that long-term memory cells for the coronavirus may also linger over time.
“The vaccines are really excellent at producing long-term memory,” Apoorva said. “And if what we’re worried about is preventing our health care system from getting overwhelmed with a lot of sick people, those who already have had two doses and maybe three doses are good to go for at least a while.”
The next animal reservoir?
Scientists discovered last fall that the coronavirus was widespread in white-tailed deer, intensifying concerns that the virus might establish itself in an animal reservoir, mutate and spread to other species, including back to humans.
And they started asking: Which animals might be next?
After the first reports of animal infections in 2020, Barbara Han, a disease ecologist at the Cary Institute of Ecosystem Studies, began working on an artificial intelligence model to narrow the field for monitoring. She and her colleagues identified 540 mammalian species that were most likely to host and spread the coronavirus.
On the shortlist are the “peridomestic” species that live alongside us but roam freely. In North America, these include deer mice, red foxes and feral cats. Officials from the U.S.D.A and other agencies are looking for signs of the virus in animals — including rodents, skunks, foxes and opossums — that live in and around zoos, wildlife facilities and mink farms.
Experts say there is no need to panic, and they emphasize that animals are not to blame for spreading the virus. But identifying the species at risk is crucial for protecting both human and animal health.
Staying ahead of the virus will require long-term funding and commitment. But scientists say making these investments now could result in better systems for monitoring pathogens in other species and an expanded understanding of how animal health is linked to ours. It may even help experts catch the next looming health threat.
“There’s no harm in understanding better the world around us,” Dr. Han said. “There can only be harm in not understanding and not investing in that knowledge, which is really obvious now.”
What else we’re following
What you’re doing
I became a nurse in the fall of 2019 and started working in the E.R. I have seen so much needless suffering and death over the last two years. Last week I treated a 7-week-old baby who caught Covid from her unvaccinated parents. They got so angry with me when I suggested that they might have prevented this from happening. This week I accepted another job offer; I’ve decided to leave the E.R. I feel terrible because we’re already short-staffed and I know that they need me, but I just can’t do this anymore.
— Brian, Bellingham, Wash.
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