The Centers for Disease Control and Prevention (CDC) has confirmed that the highly transmissible BA.5 Omicron subvariant is now the dominant coronavirus strain in the United States, accounting for roughly 54 percent of all Covid-19 infections last week.

According to the Wall Street Journal, BA.5 surpassed BA.2.12.1, the version of Omicron partially responsible for the surge in springtime cases, which is now estimated to represent about a quarter of all cases. Combined, BA.5 and the sub-strain BA.4—first discovered earlier this year in South Africa—now make up 70 percent of all reported cases.

“BA.4 and BA.5 have come out of nowhere the last two weeks.” Dr. Roy Gulick, chief of the division of infectious diseases at New York-Presbyterian and Weill Cornell Medicine, explained to ABC News. “They are more transmissible than the other recent variants we've seen, they're less susceptible to antibodies both from previous infection or from vaccination—but they don't seem to cause more severe disease,” Gulick added.

The news comes a week after the Food and Drug Administration (FDA) recommended that all vaccine manufacturers update their coronavirus vaccine booster shots by the fall to target BA.4 and BA.5, in anticipation of a wider Covid-19 surge this winter.

“As we move into the fall and winter, it is critical that we have safe and effective vaccine boosters that can provide protection against circulating and emerging variants to prevent the most severe consequences of COVID-19,” Dr. Peter Marks, director of the Center for Biologics Evaluation and Research at the FDA, said in a statement.

“Following a thorough discussion … an overwhelming majority of the advisory committee voted in favor of including a SARS-CoV-2 omicron component in COVID-19 vaccines that would be used for boosters in the U.S. beginning in fall 2022,” he added.

As reported by CNN, vaccine makers Moderna and Pfizer/BioNTech have already tested new versions of their vaccines and presented data to the independent FDA advisers.

“Based on the strength of our initial data from our Omicron BA.1 bivalent candidates, we believe we have a strong solution with a bivalent BA.4/BA.5 subvariant booster as we head into this next chapter of the pandemic, and will continue to share our available data with health experts and regulators,” a Pfizer spokesperson reported in a statement. “We are ready to distribute a vaccine to the world by early October 2022, pending regulatory authorizations,” the statement continued.

Meanwhile, largely fueled by the BA.5 strain, a new and potentially deadly coronavirus wave appears to have started in New York City. Dr. Jay Varma, an infectious diseases physician and Mayor Bill de Blasio's former senior advisor for public health, claimed that recent data indicate that Covid-19 infections in the city have continued to stabilize at elevated levels.

“The decline of reported #COVID19 cases in NYC has stopped. Reported cases are at a high plateau, which means actual transmission is very high when you account for the >20x under-counting. This is likely the beginning of a BA.5 wave,” Varma tweeted, per NBC New York.

“Experience from other countries means there will be another big increase in NYC #COVID19 infections, including among those who have had #Omicron in past few months,” he concluded.

Ethen Kim Lieser is a Washington state-based Finance and Tech Editor who has held posts at Google, The Korea Herald, Lincoln Journal Star, AsianWeek, and Arirang TV. Follow or contact him on LinkedIn.

Image: Reuters.