The growing dominance of two new ultra-contagious Omicron subvariants is prolonging a wave of coronavirus cases in California, raising concerns among public health officials that there could be significant spread and increased hospitalizations in the coming weeks.
BA.4 and BA.5 are believed to be responsible for most new infections nationwide. The strains are of particular concern because not only are they particularly contagious, but they can also re-infect those who have survived a previous Omicron infection.
When it comes to BA.4 and BA.5, their “superpower is reinfection,” said Dr. Peter Chin-Hong, an infectious disease expert at UC San Francisco.
In addition, “there is strong evidence that they can spread even faster than other subvarieties,” said Barbara Ferrer, director of public health for Los Angeles County.
“There were also some worrying results in laboratory studies, showing that BA.4 and BA.5 were better able to infect lung cells than Omicron’s earlier BA.2 subvariant,” she said.
BA.4 and BA.5 are likely to affect countries and regions differently depending on overall immunity levels and the number of elderly and medically vulnerable people. But “all information to date indicates that we need to prepare for the likelihood of significant transmission in the coming weeks,” Ferrer said.
“Due to the uncertainty of exactly how these new subvariants will affect us in LA County, it remains important to take all measures that will help reduce the risk of COVID-19,” such as vaccinations, masks, outdoor exercise activities, increasing ventilation if they’re indoors, testing and staying home if they’re sick, she said.
Although reinfections with the coronavirus have been possible throughout the pandemic, the risk has recently increased.
“BA.4 and BA.5 are of particular concern because they appear to have the ability to reinfect people who have previously been infected with other Omicron subvariants,” Ferrer said.
From early December, when Omicron’s presence was first detected in California, through late February, the state reported an average of about 14,325 people newly infected with the coronavirus each week, according to the California Department of Health and Human Services.
That number then declined along with the first Omicron wave, with an average of 2,315 weekly new infections reported from early March to early May.
But the metric has skyrocketed since – with 10,409 weekly new infections reported from mid-May to mid-June. This timeline roughly corresponds to the time when BA.4 and BA.5 began to spread further.
“It is likely that the increase in the total number of reinfections is due to changes in the epidemiology of COVID-19, trends in case rates and immunizations,” as well as improvements in data collection, including the implementation in February of automated processing for new reinfections , the California Department of Health said in a statement to The Times.
BA.4 and BA.5 accounted for an estimated 52.3% of cases in the one-week period ended June 25, according to the latest figures from the US Centers for Disease Control and Prevention. This is the first time the couple has represented a combined majority of estimated cases nationwide.
In the previous week, the subvariants accounted for an estimated 37.4% of cases. The proportions are similar in the US Southwest, which includes California, Arizona, Nevada, Hawaii and the US Pacific Territories.
While the ultimate impact of the two strains remains to be seen, their apparent ability to reinfect humans threatens to weaken one of the few guard rails for a pandemic-weary population.
Previous waves ended because the coronavirus hit a wall and stalled when enough people were vaccinated, infected, or changed their behavior enough to deprive the virus of vulnerable hosts.
But in a world dominated by BA.4 and BA.5, those infected with the coronavirus – even a few weeks ago – may not be adequately protected.
“The risk of reinfection is significantly increased because of the new spike mutations we are exposed to,” wrote Dr. Eric Topol, director of the Scripps Research Translational Institute in La Jolla, in a recent blog post. The first omicron variant “induces a fairly weak, narrowly defined immune response that doesn’t help with exposure to newer omicron strains,” he added.
Topol called BA.5 “the worst version of the virus we’ve seen.”
“It takes immune escape, which is already extensive, to the next level and as a function of this, enhanced transmissibility that far exceeds Omicron (BA.1) and other variants of the Omicron family that we have seen,” he wrote in another blog post. “You could say it’s not that bad because there hasn’t been a significant increase in hospitalizations and deaths like we’ve seen with Omicron, but that’s only because we’ve had such a noticeable adverse effect from Omicron, for them there at least some cross-immunity.”
The shifting subvariant dynamics could help explain why the coronavirus is still transmitting at high levels across California, daunting hopes of an end to the pandemic.
“I’m concerned because we’re seeing more BA.4 and BA.5 in our population and that might be why we’re treading water at such a high level of transmission,” Dr. Paul Simon, chief science officer for the LA County Department of Public Health, said during a recent briefing.
According to data released Friday, California has seen a 12% increase in coronavirus cases compared to mid-June, averaging more than 16,900 a day over the past week, according to data compiled by The Times. Per capita, that is 303 cases per week per 100,000 inhabitants.
A rate of 100 or more cases per week per 100,000 population is considered a high transmission rate
Los Angeles County is reporting nearly 5,300 cases per day, for a weekly rate of 367 cases per 100,000 people. That’s the highest case rate since early February and represents a 20% week-on-week increase in cases, erasing case rate improvements seen in mid-June.
This still-strong spread can be attributed to several factors, including residents who have largely abandoned infection-prevention measures and returned to pre-pandemic habits, the emergence of increasingly contagious strains, and the waning of virus immunity.
It was comparatively easier to avoid last summer’s Delta variant, or even the first Omicron strain to hit after Thanksgiving, than the more portable Omicron strains that have sprung up since.
dr Anthony Fauci, President Biden’s chief medical adviser, first tested positive for the coronavirus two and a half weeks ago. Xavier Becerra, Secretary of the US Department of Health and Human Services, tested positive in Sacramento in mid-June – about 3½ weeks after the first positive test during a visit to Berlin.
dr Abraar Karan, an infectious disease expert at Stanford University, wondered if Becerra’s June bout of COVID-19 was caused by BA.4 or BA.5. On TwitterKaran described how he contracted the coronavirus in January, likely with the first Omicron variant, BA.1, but then became infected again in May, likely with BA.2.12.1.
“With more immune-avoidable variants, that could soon be the case again for many of us,” Karan said wrote.
Any infection – whether it’s a first or a repeat occurrence – still poses potential health problems. While much has been said about Omicron’s comparatively milder nature, it can still pack a punch.
Even if no hospitalization is required, COVID-19 can still cause pathetic symptoms. And a long COVID, in which symptoms like fatigue, brain fog, or trouble breathing can persist for months or years, remains a risk after any infection, although it’s likely to be reduced by updating vaccinations.
“It is prudent to remain cautious despite the decline in hospital admissions and deaths in recent months,” wrote Dr. Robert Wachter, Chair of the Medical School at UC San Francisco lately, adding that he has stopped dining in public indoor spaces given the high case numbers in his city. “It’s all about long COVID – both prolonged symptoms and the increased long-term risk of [a heart attack]stroke, diabetes and more.”
It’s a risk he’s all too familiar with. His wife is still battling symptoms weeks after her first infection.
“As a healthy 64-year-old who was vaccinated and boosted, she had an uneventful first battle with the virus. However, seven weeks later she is still suffering from extreme fatigue and feels like her brain is working in slow motion,” Wachter wrote in a comment.
Whether BA.4 or BA.5 cause more severe diseases than other members of the Omicron family is still unclear.
Although the World Health Organization recently noted that the evidence currently available does not indicate a change in the disease’s associated severity, the agency also said its growing prevalence in several regions “coincided with increases in cases,” with those increases leading to a Increase in hospital admissions in some countries.
BA.5, Topol said, “resulted in a significant increase in hospital admissions in Portugal, where it quickly became dominant,” and has a similar effect in many European countries and Israel.
There were reports that a wave powered by BA.4 and BA.5 in South Africa was associated with slightly lower death rates than their first Omicron waves, Ferrer said. But even in Portugal, “the rise in BA.4 and BA.5 appears to be associated with a mortality rate quite similar to the first omicron wave,” she said.
It wouldn’t be a surprise if the ability of existing vaccines to protect against serious diseases diminishes when tested against BA.5, Topol said. After all, the vaccines plus booster dose resulted in a 95 percent protection against serious diseases caused by the Delta variant, but that dropped to 80 percent when tested against early Omicron variants BA.1 and BA.2, he said .
A key question is whether the potential introduction of an Omicron-specific booster later this year will help. Given how much the variant has changed over the past seven months, there are concerns that such an offering could be relatively outdated by the time it becomes available.
It’s increasingly important, Topol said, to speed up work on a new generation of vaccines, such as a nasal vaccine designed to better protect people from infection and vaccines that can work against all variants of the coronavirus.