Can You Be Immune To COVID19?
While we all hope that making it through one COVID infection means we are “safe,” we do not yet know if, or for how long, immunity may last. Successfully fighting a virus involves much more than antibody levels. There is an “innate immune system” response and an “adaptive immune system” response, which orchestrates specialized T-cells and memory cells, messenger cells, signaling molecules, and much more. The immune system is impressively complex but as Ed Yong writes: Immunology is where intuition goes to die. “Crucially, researchers still don’t know how much protection the leftover antibodies, T-cells, and memory cells might offer against COVID-19, or even how to measure that.”
In July, a team from King’s College London showed that many patients lose substantial amounts of their coronavirus-neutralizing antibodies after just a few months. Another study in June from a team in China, found similar results. Both raised the alarm that people could be infected repeatedly or even that a vaccine might not provide long-term protection. But, Yong writes, “many of the immunologists I spoke with weren’t too concerned, because — and reassuringly this time — the immune system is really complicated. A decline in antibody levels over time is expected. Antibody quantity is not the only thing that matters, the “quality” of the antibody is just as important. Quality might mean where on the virus it attaches or how well it sticks. Many people who recover from COVID-19 have low levels of neutralizing antibodies, but some of them neutralize very well.
Research on other coronavirus may help inform how long protective immunity lasts. For the severe ones, like MERS and the original SARS, it lasted at least a couple of years. For milder ones that cause the common cold, it disappears within a year. It is reasonable to guess COVID immunity will lie between those extremes, but we just don’t have the answer yet.
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