Flam: There’s good news about coronavirus immunity, but don’t bet your life on antibody tests

A mere month ago, the idea of immunity passports had raised hopes that people who survived COVID-19 would be freed from indefinite, costly confinement. Scientists warned, though, that our immune systems, while natural wonders, don’t always provide iron-clad protection against future viral attack. This virus was too new to know.

Now scientists have new evidence that our immune systems do retain various powerful defensive weapons after SARS-CoV2 is cleared. This is critical new information. Here’s a quick update on this and other recent developments in what we know about COVID-19 immunity:

Immunity is more than just antibodies

A new paper in the journal Cell showed that people who’ve recovered from COVID-19 not only have antibodies, but retain immune system components known as T-cells, which, among other things, can clear the virus by killing infected cells.

The researchers compared 10 people who had been infected with 11 control subjects and determined that those who had fought off infections were armed with not only antibodies but also with CD4 cells, sometimes called a helper T-cells, which are important for getting a good antibody response. They also retained CD8 cells, or killer T-cells, which kill cells that are infected with the virus.

It’s reasonable to assume most people who’ve had COVID-19 are less likely to be re-infected, and less likely to get a severe case if they do, says Florian Krammer, a professor at the Icahn School of Medicine at Mount Sinai and co-author of the paper.

What they still don’t yet know, Krammer says, is whether the immune response is good enough to prevent people from picking up a second, milder infection and transmitting it. He’s involved in a long-term study that will follow people who’ve had the disease for a year to see how often, if ever, they get re-infected.

The Cell study showed that about half of people who had never had COVID-19 carried T-cells leftover from infections with other coronaviruses. (About 30% of common colds are caused by coronaviruses.) While some early news reports hinted that cold-induced T-cells might protect people from COVID-19, Krammer says they’re unlikely to play a big role. Everyone has had a cold-causing coronavirus in the past, and there’s little indication this is helping anyone avoid COVID-19.

Another study released this week in Science bolstered the evidence for post-infection immunity by attempting to deliberately infect monkeys twice. A week after the monkeys recovered from an initial infection induced by spraying particles of virus into their noses, the researchers again exposed the monkeys to this same “challenge.”  The monkeys resisted a second infection. That group, led by Harvard’s Dan Barouch, also performed a similar challenge study on monkeys that had not been previously infected but had been given an experimental vaccine based on DNA that holds the code for viral proteins needed to stimulate the immune system. Those monkeys, too, resisted getting infected. Those results were published in a second Science paper.

This is good news for vaccine developers

The findings on coronavirus immunity gives new reason for optimism that it will be possible to artificially induce an immune reaction with a vaccine.