Thread by @bopinion

It’s been about a year since the early coronavirus alarms were raised, and despite a decline in infections, fears are rising.

New Covid-19 variants are making pessimists worry that an even bigger wave may be coming trib.al/zy0fj0N

It’s true that the virus is mutating in ways more profound than biologists anticipated last summer.

But new research suggests that there may be limits to how many tricks Covid-19 has up its sleeve — and that may make it easier for vaccines to keep up trib.al/zy0fj0N

If scientists have been blindsided by the variants, it’s because they hadn’t realized that this virus tends to mutate in a way that’s distinct from influenza or HIV.

Covid-19 has a talent for shape-shifting by dropping pieces of its genetic code trib.al/zy0fj0N

Early on, a few scientists observed these so-called deletion mutations by studying virus samples from patients with compromised immune systems.

Such patients can be crucibles for viral evolution, because the virus survives in their cells for months trib.al/zy0fj0N

The mutations were essentially the same as those now seen in the new variants. Molecular biologist Kevin McCarthy found this eye-opening.

“Evolution in that patient, in some ways, foreshadowed what the virus was going to do all over the world,” he said trib.al/zy0fj0N

When a mutated virus replicates, a mechanism normally corrects it.

Covid-19’s proofreader lets one type of mutation through: a section of missing genetic code. The virus is able to eject sections of code and still get transmitted to other people trib.al/zy0fj0N

The deletions can allow viral proteins to change their shapes in ways that could evade both proofreading and the immune system.

That’s what people are worried about. The B.1.1.7 variant that spread so fast in the U.K. has two of these deletions trib.al/zy0fj0N

B.1.1.7’s big advantage is an increased ability to transmit between people.

It’s also a basic principle of evolution: the more that humans produce antibodies to a virus, the greater will be the advantage for any new variant that can elude those antibodies trib.al/zy0fj0N

If the coronavirus develops an anti-vaccine strategy, we will need a counter strategy.

That could mean upgrading existing vaccines. It also might help to give people different vaccines for their first and second doses trib.al/zy0fj0N

This fight requires that all scientists working to understand the virus have all the data they need.

But from what they’ve learned so far, it doesn’t appear that the new variants mean the pandemic will never end trib.al/zy0fj0N

SARS-CoV-2 may not be able to mutate itself in infinite ways that make it better at infecting people and evading antibodies.

So far, scientists have been seeing the same deletions cropping up again and again trib.al/zy0fj0N

As the complexities of the coronavirus have become apparent, scientists have grown less confident in their predictions.

But there’s no reason to assume the pandemic will never go away trib.al/zy0fj0N