You’re reading The Checkup With Dr. Wen, a newsletter on how to navigate covid-19 and other public health challenges. Click here to get the full newsletter in your inbox, including answers to reader questions and a summary of new scientific research.
Scientists have raised alarms in recent weeks about a new, highly mutated coronavirus variant that might evade the protection of existing immune defenses. The variant, an offshoot of omicron named BA.2.86, requires careful attention by public health experts. But just like the summer uptick in coronavirus cases, it is not yet cause for concern for most Americans.
It’s not at all surprising that new variants are constantly emerging. As we have seen throughout the pandemic, when viruses replicate, they acquire mutations.
Whether a new set of mutations has public health consequences hinges on three key questions: Does it cause more severe disease? Will immunity through prior infection and vaccination protect against it? And is it more transmissible than currently dominant variants?
On the first question, there are too few cases of BA.2.86 to know whether people infected with it will become sicker than those who contract other omicron descendants. The good news is that the Centers for Disease Control and Prevention expects existing treatments — specifically antiviral pills Paxlovid and molnupiravir and remdesivir injection — to be effective against the new variant. These are crucial tools that dramatically reduce the chance of being hospitalized or dying because of covid-19.
The second question is what’s most worrying to scientists. The genetic sequence of BA.2.86 has more than 30 amino acid differences compared with the BA.2 subvariant it evolved from. It also has significant deviation from the XBB.1.5 subvariant, which has been the dominant variant throughout much of 2023 and is the target of the new booster that’s on track to be released in late September.
Will the new booster be as effective against BA.2.86 as it is against XBB.1.5 and other currently circulating variants? No one knows the answer to this yet, but the number of mutations and where they are located are prompting urgent laboratory studies.
These studies will examine whether the potential immune evasiveness affects protection against infection or severe disease. This is a significant distinction. It might be the case that prior immunity is not as protective against infection, meaning that people who previously contracted the virus could be more susceptible to reinfection, as would those who are up to date with their vaccines. But far more important is whether individuals with immunity against prior variants remain well-protected against severe disease.
When omicron arrived, researchers quickly realized that people who contracted earlier coronavirus variants, such as alpha and delta, were being reinfected and that vaccine effectiveness against infection was much lower for omicron than during earlier surges. But existing immunity was still a good shield against severe disease.
If BA.2.86 follows a similar trajectory to the emergence of omicron, the negative public health impact would be blunted, especially because the availability of antivirals that further reduce disease severity is far greater than during the omicron surge in late 2021 and early 2022.
At that time, omicron caused great societal disruption. The main reason for this is its high degree of transmissibility. Herein lies the third crucial question, for which we also don’t yet know the answer: Is BA.2.86 so highly contagious that it will outcompete other variants?
Based on what we’ve seen thus far, this does not appear to be the case. There have been very few BA.2.86 cases detected to date, including a small number reported in the United States. Even if it is more immune-evasive, this new variant won’t have a meaningful impact unless it becomes more prevalent and displaces other variants.
None of this is meant to downplay the potential significance of this highly mutated offshoot. If BA.2.86 ends up increasing as a proportion of total cases and the worst-case scenarios about its immune evasiveness end up being true, a change in strategy will be needed. That includes a discussion of whether the new booster shot should be reconfigured to take this variant into account.
Those vulnerable to severe disease from covid-19 should continue to take precautions — not necessarily to avoid the small possibility of contracting this variant but to reduce their chance of becoming ill from the dominant variants. Vulnerable people should discuss with their health-care providers the optimal timing of the booster and be sure to have a plan for antiviral treatment if they become ill.
For now, though, most Americans do not need to change their daily lives. This is not the moment to bring back government-mandated mask requirements and other broad public health restrictions. Those measures should be reserved for a true emergency, which we currently do not have.