It is the BA.5 of Omicron that is currently estimated to account for about 88.6% of new infections, as per the CDC. This period of stagnation in the emergence of new variants and sub-variant of COVID has baffled scientists.
When Covid was declared a pandemic during the first quarter of 2020 to this date the virus has been changing. With these mutations, there has been constant monitoring of dominant variants at a given time across countries.
However, for the last five weeks, US federal data shows that there has been little to no growth in the different proportions of COVID-19 variants in the country. Currently, only B.1.1.529 subvariant of Omicron is listed as a Variant of Concern (VOC) by WHO.
For more than nine months, the omicron variant, and its subvariants, have been dominant in most countries of the world.
But now, health experts say it is unclear why the evolution of even the omicron subvariants appears to have stalled, or why it is that no other major significant variants have emerged to challenge its dominance of Omicron as it happened with highly transmissible Alpha, Beta, and delta variants.
“Unlike previous variants, BA.5 appears to have more staying power. A mix of higher transmissibility, waning immunity and relaxed restrictions likely contribute to the ability of this variant to find more hosts to infect,” said John Brownstein, Ph.D., an epidemiologist at Boston Children’s Hospital and an ABC News contributor.
BA.5 is currently estimated to account for about 88.6% of new COVID-19 infections — a share that has plateaued over the last five weeks, according to updated data from the Centers for Disease Control and Prevention.
BA.4 currently accounts for an estimated 2.8% of new cases in the U.S., and a recently identified subvariant, BA.4.6, is estimated to account for 8.4% of new cases — up slightly from last week when the subvariant accounted for 7.6% of new cases.
Combined, the BA.4 and BA.5 subvariants account for nearly 100% of new cases in the U.S., according to the CDC data. Most other countries are witnessing similar trends over a period of time.
The BA.4 and BA.5 subvariants seem to have a transmission advantage over the original omicron strain, according to the World Health Organization, and thus, scientists have been closely monitoring the increase in reported cases. At this time, it does not appear as though BA.5 has increased in severity.
Compared with the earlier Omicron BA.2 subvariant, currently dominant Omicron BA.5 is linked with higher odds of causing a second SARS-COV-2 infection regardless of vaccination status, a study from Portugal suggests.
However, 10% of BA.5 cases were reinfections, compared to 5.6% of BA.2 cases, which suggests a reduction in the protection provided by the previous infection against BA.5 compared to BA.2, the researchers said. Moreover, the vaccines appeared to be less effective in reducing the risk of severe outcomes for BA.5 compared with BA.2.
From late April this year to early June, researchers studied 15,396 adults infected with the BA.2 variant and 12,306 infected with BA.5. The vaccines and boosters were equally effective against both sublineages, according to a report posted on medRxiv ahead of peer review.
Will the coming winter see a resurgence of new major variants?
The slowing of the omicron strain’s growth pattern leaves many questions unanswered as to whether there will be viral resurgence in the fall and winter.
“We still have open questions as to what this means for a fall surge and the opportunities for a new variant to displace it,” Brownstein said.
The stagnation of growth with the omicron variants comes as the U.S. appears to experience a parallel plateauing of new COVID-19 infections. The nation had been reporting consistent declines throughout the late summer, but in recent weeks, that number has been hovering around 84,000 new cases each day, according to the CDC.
As previously reported, dozens of states have moved to shutter public testing sites, with more at-home COVID-19 tests now available. Most Americans are not reporting their results to officials, and thus, experts suggest that infection totals are likely significantly undercounted.
Just over 400,000 tests are being reported each day, marking the lowest number of confirmed tests since the onset of the pandemic.
Although new case rates are still dropping in parts of the West, across areas of the Northeast, the Midwest, and even parts of the South, case rates have plateaued at a high level or are showing signs of increasing again.
Hospital admission levels also appear to be plateauing nationally. About 5,100 virus-positive Americans are entering the hospital each day, down by about 3.7% in the last week, according to CDC data.
Death rates also remain persistently high, with hundreds of Americans still losing their lives to the virus each day. According to the CDC, the average number of daily COVID-19-related deaths remains at more than 400 deaths reported each day.
Thousands are still losing their lives every week, and over the last seven days alone, the U.S. has reported more than 2,800 deaths — still one of the highest weekly totals in months.