Two years into the coronavirus pandemic, Americans can be forgiven for losing track of the latest variants circulating nationally and around the world. We’ve heard about the Alpha, Beta, Gamma, Delta, and Omicron variants, but a new variant with Greek letters hasn’t hit the market for almost half a year.
Instead, a seemingly never-ending stream of “sub-variants” of omicron, the latest variant of the Greek letter, has sprung up in recent months.
How do these sub-variants differ from each other? Can infection by one subvariant protect someone from infection by another subvariant? And how well do the existing coronavirus vaccines — developed before the advent of omicron — do against the subvariants?
We asked medical and epidemiological experts these and other questions. Here is an overview.
Q: What are the sub-variants? How different are they from each other?
The omicron subvariants look like an alphabet soup of letters and numbers. The original omicron variant was called B.1.1.529. The initial Omicron variant spawned subvariants such as BA.1; BA.1.1; BA.2; BA.2.12.1; BA.3; and the newest, BA.4 and BA.5.
“They all differ from one another by having different mutations in the spike protein,” which is the part of the virus that enters host cells and causes infection, said Dr. Monica Gandhi, Professor of Medicine at the University of California-San Francisco.
The minor to moderate mutations in these subvariants may make them slightly more transmissible from person to person. In general, the higher the number after “BA” in the subvariant name, the more portable that subvariant is. For example, BA.2 is believed to be about 30% to 60% more portable than previous subvariants.
These mutations have allowed subvariants to spread widely, only to be overtaken within a few weeks by a slightly more transmissible subvariant. Then the process repeats itself.
For example, in the United States, BA.1.1 was dominant in late January after overtaking initial variant B.1.1.529. But in mid-March, BA.1.1 began to lose ground to BA.2, which became dominant in early April. In late April, another subvariant — BA.2.12.1 — gained momentum, accounting for nearly 29% of infections, according to the Centers for Disease Control and Prevention. (The late 2021 delta wave was not a factor in this period.)
Q: What about the severity of the disease?
Fortunately, the diseases caused by Omicron were typically less severe than those caused by previous variants – a pattern that seems to hold true for all subvariants studied so far. An analysis from Denmark showed that BA.2 causes no more hospital admissions than the BA.1 subvariant, Gandhi said.
Even the most recently discovered subvariants, BA.4 and BA.5, “show no evidence that it is any more worrisome than the original omicron, other than a possible slight increase in transmissibility,” said Brooke Nichols, an infectious -disease mathematical modeler at the Boston University.
Dennis Cunningham, systems medicine director for infection control and prevention at Henry Ford Health in Detroit, told NBC News that the symptoms of the Omicron subvariants were “fairly consistent. It is less common for people to lose their sense of taste and smell. In many ways it is a bad cold, lots of breathing difficulties, stuffy nose, cough, body aches and fatigue.”
Q: If you get infected by one subvariant, are you protected from others?
So far, the ability of the virus to evade the existing immune protection is “only partial, similar to seasonal flu,” said Colin Russell, professor of applied evolutionary biology at the Faculty of Medicine at the University of Amsterdam Center.
While some people who had BA.1 also got BA.2, initial research suggests that infection with BA. 1 “provides strong protection against reinfection with BA.2,” according to the World Health Organization.
“This could explain why our BA.2 surge in the US was not as large as the very large BA.1 surge in the winter,” Gandhi said.
The level of protection can vary depending on how ill you’ve been, with mild cases bolstering immunity for perhaps a month or two and recovery from serious illness granting up to a year.
Q: How do existing COVID-19 vaccines compare to these subvariants?
Although current vaccines and booster shots are not quite as effective in protecting against Omicron as they are against previous variants, they generally protect people from serious illness when infected with any of the new subvariants.
“We are consistent with the vaccines we use,” said Dr. William Schaffner, Professor of Preventive Medicine and Health Policy at Vanderbilt University. “I have not seen a single study from this area that shows a significant difference between vaccination responses to Omicron subvariants.”
The vaccines create cells known as “memory B cells,” and they have been shown to recognize different variants as they arise, Gandhi said. The vaccines also trigger the production of T cells, which protect against serious disease, she said.
“While B cells serve as memory stores to produce antibodies when needed, T cells amplify the body’s response to a virus and help recruit cells to attack the pathogen directly,” Gandhi said.
The bottom line is that a breakthrough infection for a vaccinated person “should remain mild with the subvariants,” she said.
The widespread spread of a relatively mild strain of the virus in the US has likely paid off by providing many Americans with some degree of immunity, whether they have been vaccinated or not. Research shows that people who were vaccinated and then infected had even greater protection than people who were vaccinated and did not contract COVID.
“This family of omicron could actually offer a positive side in the wake of the pandemic,” said Schaffner.
Looking ahead, vaccine makers are beginning to develop vaccines specifically targeting Omicron, and some would combine a coronavirus vaccine with a seasonal influenza vaccine all at once. But those vaccines are in the early stages, and Schaffner said he suspects they won’t be ready and approved by the time of flu vaccination season this fall.
Whether such new vaccines represent the next step in the fight against COVID depends on the FDA and the CDC.
Q: Are completely new variants on the horizon?
Experts agreed that the only new arrivals in recent weeks have been incremental subvariants – certainly nothing that seems as groundbreaking as Delta or Omicron did when they first appeared.
“We’re not yet aware of anything lurking, and the surveillance is pretty damn aggressive,” Schaffner said.
There are estimates that more than 60% of the world’s population has been exposed to Omicron and over 65% of the world’s population has received at least one dose of the vaccine, Gandhi said, “so I’m keeping my fingers crossed that the development of new variants will slow down with this level of population immunity.” .”
Gandhi admitted to being surprised at how calm the horizon is at the moment, but she sees it as a positive development.
“It has now been five months since we heard of a new variant, which we hope will reflect the increasing immunity of the world population,” she said.
https://www.sltrib.com/news/health/2022/05/09/guide-help-you-keep-up/ A guide to help you keep up with the Omicron subvariants