ワクチン接種は中和抗体の産生を促すだけでなく、免疫に重要なT細胞 (色々な変異株に対して防御能力が広範な免疫能を担う) の産生を促すので、ワクチン接種は今後の変異株に対しても重要な感染対策となる

What to Know About BA.2, a New Omicron Variant

BY ALICE PARK / JANUARY 28, 2022 / TIME

わたしのnoteにおいては、最新の科学・経済・社会等の問題に関して、英語の記事を引用し、その英文が読み易いように加工し、「英語の勉強ツール」と「最新情報収集ツール」としてご利用頂くことをmain missionとさせて頂きます。勿論、私論を書かせて頂くこともしばしです。

Even as SARS-CoV-2 gets better at spreading and evading some of the immune protection that people have built through infections or vaccination, new variants inevitably arise. The latest is BA.2, a new version of Omicron.

It’s too early to predict what BA.2 might mean for the course of the COVID-19 pandemic. But detecting such variants early will help public health experts better identify which ones pose the most danger to people’s health, and therefore require more stringent mitigation measures. Here’s what we know so far.

What is the BA.2 variant?

BA.2 appears to be a descendant of Omicron (which researchers are now referring to as BA.1). Researchers at the World Health Organization reported increasing numbers of BA.2 infections in January in Denmark, India, and the U.K. Even though it’s been just a few days since the variant was identified, South Africa and the U.S. have also reported cases of BA.2. So far, the virus has been detected in four U.S. states: California, New Mexico, Texas, and Washington. Scientists found BA.2 thanks to more widespread genetic sequencing, which is helping them detect changes in SARS-CoV-2 more quickly and determine how those mutations might affect human health.

Is the new BA.2 variant more dangerous than Omicron?

Like Omicron, BA.2 contains numerous mutations, according to researchers at the Massachusetts Consortium on Pathogen Readiness, a collaboration of academic researchers from different institutes in the Boston area who monitor genetic changes in SARS-CoV-2. About 20 mutations have been located in the antibody-binding regions that vaccines target. BA.2 also contains some mutations not found in BA.1, but scientists aren’t sure yet what those changes mean.

Should you be worried?

The WHO has not determined yet whether BA.2 as a variant of concern. So far, there isn’t enough information to determine how transmissible or virulent BA.2 might be, although in South Africa, BA.2 is now more prevalent than BA.1. It’s not yet clear whether BA.2 is more transmissible than Omicron.

Will the current COVID-19 vaccines work against BA.2?

It’s still unknown, but the good news is that there is growing evidence that vaccines generate both immediate and longer lasting immunity against all variants of SARS-CoV-2 so far. The antibodies that the shots catalyze may only protect against infection for a relatively short amount of time—Moderna reported this week that even after a booster dose of its vaccine, these virus-neutralizing antibodies tend to wane after six months—but the body’s immune response to vaccination also includes T cells. These are more durable and are aimed at more conserved regions of the virus; T cells seem to provide good and lasting protection against severe disease from every variant so far, even if people do get infected.