With the arrival of the fall and winter seasons, experts are keeping a close eye on emerging coronavirus variants and their potential to cause a new COVID-19 surge.
Two of the pandemic’s worst surges to date — in January 2001 from the delta variant and January this year from the original omicron variant — occurred as the weather cooled, and many people traveled and gathered indoors for the holidays.
This year is different, experts say, with multiple vaccines and an updated booster shot available, more natural immunity as an ever-larger proportion of the population contracts the virus, and a number of treatment options for those who do fall ill.
However, despite the current lull, the omicron strain and its many subvariants are still circulating. Each new variant to gain dominance has proved more transmissible than the last, with many appearing better able to evade immunity from vaccines and prior infection — though rates of hospitalizations and deaths are far lower than earlier in the pandemic.
The BA.5 omicron subvariant is still the dominant strain in the U.S. after appearing in late spring and quickly crowding out its rivals, accounting for nearly 90% of cases in late August. However, its share has since fallen to 81%, while the omicron offshoot BA.4.6 is slowly growing, responsible for 13% of cases for the week ending Oct. 1.
A pandemic pattern
Concerns about a possible new surge arise from a combination of three factors: human behavior, the evolution of the virus and overall waning immunity protection from vaccines and prior infection, said UCSF infectious disease expert Peter-Chin Hong.
And a recent rise in cases and hospitalizations in Europe, which has often been a COVID bellwether for the U.S., is heightening the unease.
“The question is not whether we will see an increase in cases and hospitalizations — we will — but by how much,” Chin-Hong wrote in an email.
Here are the omicron offshoots experts are monitoring closely, and why:
BA.2.75.2
Share of U.S. cases: 1.4%
What we know: This offshoot of BA.2.75, which caused a surge in India several months ago, is the best among the crop of new variants at evading immunity due to mutations in the spike protein, Chin-Hong said.
It’s uncertain how long boosters will protect against even mild infections with this variant, Chin-Hong said, but he added that the shots “will likely continue to perform extremely well at preventing hospitalizations and deaths.”
A study published earlier last month found this variant had “profound antibody escape” and suggests that it can escape current immunity in the population. The study also found that the variant could reduce the effectiveness of Evusheld, the monoclonal antibody treatment for immunocompromised individuals.
BF.7
Share of U.S. cases: 3.4%
What we know: Also known as BA.5.2.1.7, BF.7 is a relative of BA.5 and has a “few more mutations on the spike protein,” Chin-Hong said. It could reduce the effectiveness of Evusheld as well as another treatment called bebtelovimab that is used to treat mild and moderate COVID in adults, he said.
BA.2.3.20
Share of U.S. cases: Has not yet appeared in CDC variant tracker.
What we know: This offshoot of BA.2 is an emerging variant in Singapore and some European countries, Chin-Hong said. It has a growth rate advantage of about 15% compared with BA.5, he said, which may fuel more infections and reinfections.
BQ.1.1
Share of U.S. cases: So far 0% on CDC variant tracker.
What we know: This variant is “extremely immune evasive” like BA.2.75.2, but does not have the “high growth advantage” of BF.7 so far, Chin-Hong said.
Nevertheless, while cases from BQ.1.1 are still a small fraction overall, its rates “have been growing rapidly,” according to Stacia Wyman, senior genomics scientist at the Innovative Genomics Institute at UC Berkeley.
“We still have sublineages of BA.2.75 to keep an eye on as well, but if they exceed the apparent growth advantage of BQ.1.1, that would not be good, as BQ.1.1. is already worrisome,” she said. “It is estimated that BQ.1.1 has a growth advantage of 14% over BA.5. This is less than omicron had over delta, but more than BA.2 had over BA.1.”
But she added that because BQ.1.1 stems from BA.5, we would have good protection against it with the new omicron-targeting bivalent boosters.
What could happen next
For the late fall and winter season, Chin-Hong outlined two possible scenarios. One is a “modest increase” of cases due to a large proportion of the population already infected this year, combined with vaccines and boosters, resulting in “a highly protected community.”
The updated vaccine booster, which is formulated to fight the original omicron strain and BA.4 and BA.5, could give the U.S. an advantage over Europe, which is using a booster that fights the original strain and BA.1, he said.
The second scenario is a “larger surge of cases and hospitalizations” because not enough people have received the updated boosters.
Last week, the Centers for Disease Control and Prevention updated its definition of what it means to be “up to date” on vaccination to be the primary vaccine series plus the updated booster. But the latest CDC data shows that only about 4% of the eligible population has gotten the new shot.
That raises the potential that “emerging variants like BF.7 that are more immune evasive may fuel more infections, which will lead to a round of disruptions in society once again: school and work absences, missed Thanksgiving dinners, short-staffed restaurants and canceled Broadway shows,” Chin-Hong said.
How to prepare for the next surge
Those who have not received their boosters should get them as soon as possible when they are eligible, Wyman said.
“I continue to be quite cautious, and what that looks like for me is wearing a good mask if I’m indoors in small spaces with other people,” she said.
She added that she would consider eating indoors at a restaurant, but only after assessing several factors including how crowded it might become, the airflow level, and whether contracting COVID would derail upcoming plans.
People will need to be more proactive on their own, watching COVID metrics including wastewater data “like the weather report,” Chin-Hong said.
Keep your masks and at-home testing kits handy, and get a flu shot in addition to the updated booster, he added.
“At the end of the day, maintain flexibility to bring out all of these tools at the drop of a hat when COVID cases rise,” he said. “When the going is good, celebrate. When the COVID clouds darken, bring out your protection temporarily until they pass.”
Kellie Hwang is a San Francisco Chronicle staff writer. Email: kellie.hwang@sfchronicle.com Twitter: @KellieHwang
#Coronavirus, #Vaccines
Published on The Perfect Enemy at https://bit.ly/3V4xeir.
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