Two years into the coronavirus pandemic, Americans can be forgiven if they鈥檝e lost track of the latest variants circulating nationally and around the world. We鈥檝e heard of the alpha, beta, gamma, delta, and omicron variants, but a new Greek-letter variant hasn鈥檛 come onto the scene in almost half a year.
Instead, a seemingly endless stream of 鈥渟ubvariants鈥 of omicron, the most recent Greek-letter variant, has emerged in the past few months.
How different are these subvariants from one another? Can infection by one subvariant protect someone from infection by another subvariant? And how well are the existing coronavirus vaccines 鈥 which were developed before omicron鈥檚 emergence 鈥 doing against the subvariants?
We asked medical and epidemiological experts these and other questions. Here鈥檚 a rundown.
Q: What are the subvariants? How much do they differ from one another?
The omicron subvariants seem like an alphabet soup of letters and numbers. The original omicron variant was called聽. The initial omicron variant begat such subvariants as BA.1; BA.1.1; BA.2; BA.2.12.1; BA.3; and the most recent,聽
鈥淭hey all differ from each other by having different mutations in the聽,鈥 which is the part of the virus that penetrates host cells and causes infection, said Dr. Monica Gandhi, a professor of medicine at the University of California-San Francisco.
The minor-to-modest mutations in these subvariants can make them marginally more transmissible from person to person. Generally, the higher the number following 鈥淏A鈥 in the subvariant鈥檚 name, the more transmissible that subvariant is. For instance, BA.2 is聽聽about 30% to 60% more transmissible than previous subvariants.聽
These mutations have enabled subvariants to spread widely, only 聽by a slightly more transmissible subvariant within a few weeks. Then the process repeats.
In the United States, for instance, BA.1.1 was dominant in late January, having overtaken the initial variant, B.1.1.529. But by mid-March, BA.1.1 began losing ground to聽,聽which became dominant by early April. By late April, another subvariant 鈥 BA.2.12.1 鈥 was gaining steam, accounting for almost 29% of infections,聽聽from the Centers for Disease Control and Prevention. (The delta wave of late 2021 has been a non-factor during this time frame.)
Q: What about the severity of illness?聽
Fortunately, the illnesses caused by omicron have typically been less severe than those caused by previous variants 鈥 a pattern that seems to hold for all the subvariants studied so far. One analysis from Denmark showed that BA.2聽聽than the BA.1 subvariant, Gandhi said.
Even the most recent subvariants that have been discovered,聽, show 鈥渘o evidence to suggest that it is more worrisome than the original omicron, other than a potentially slight increase in transmissibility,鈥 said Brooke Nichols, an infectious-disease mathematical modeler at Boston University.
Dennis Cunningham, the system medical director of infection control and prevention at Henry Ford Health in Detroit,聽聽that the symptoms from the omicron subvariants 鈥渉ave been pretty consistent. There鈥檚 less incidence of people losing their sense of taste and smell. In a lot of ways, it鈥檚 a bad cold, a lot of respiratory symptoms, stuffy nose, coughing, body aches, and fatigue.鈥
Q: If you get infected by one subvariant, will you be protected against others?
So far, in all variants to date, the ability of the virus to evade existing immune protection 鈥, much like it is for the seasonal flu,鈥 said Colin Russell, a professor of applied evolutionary biology at the University of Amsterdam鈥檚 medical center.
While some people who had BA.1 have also gotten BA.2, the initial research suggests that infection with BA. 1 鈥減rovides strong protection against reinfection with BA.2,鈥 the World Health Organization聽.
鈥淭his may explain why our BA.2 surge in the U.S. was not that large as the very large BA.1 surge over the winter,鈥 Gandhi said.
The level of protection can vary depending on how sick you were, with mild cases boosting immunity for perhaps a month or two and recovery from a severe illness granting up to a year.
Q: How do existing covid-19 vaccines stack up against these subvariants?
Although the current vaccines and boosters aren鈥檛 quite as successful in protecting against omicron as they are against earlier variants, they will generally protect people from severe disease if they are infected by one of the new subvariants.聽
鈥淲e鈥檙e steady as she goes with the vaccines we鈥檙e using,鈥 said Dr. William Schaffner, a professor of preventive medicine and health policy at Vanderbilt University. 鈥淚 have not seen a single study from the field that shows a substantial distinction between the vaccine responses to omicron subvariants.鈥
The vaccines聽聽known as 鈥渕emory B cells鈥 and聽聽to recognize聽聽as they emerge, Gandhi said. The vaccines also trigger the production of T cells,聽, she said.聽
鈥淲hile B cells serve as memory banks to produce antibodies when needed, T cells amplify the body鈥檚 response to a virus and help recruit cells to attack the pathogen directly,鈥 Gandhi said.聽
The end result is that a breakthrough infection for a vaccinated individual 鈥渟hould remain mild with the subvariants,鈥 she said.
The wide spread in the U.S. of a relatively mild strain of the virus likely paid dividends by providing many Americans with some immunity, whether or not they had been vaccinated. Research shows that people who had been vaccinated and then were infected had even greater protection than people who had been vaccinated and not gotten covid.
鈥淭his family of omicron could indeed offer a bright side鈥 in the course of the pandemic, Schaffner said.
Looking ahead, vaccine manufacturers are beginning to design vaccines that specifically target omicron, and some would combine a coronavirus vaccine with a seasonal influenza vaccine in one shot. But these vaccines are in their early stages, and Schaffner said he suspects they won鈥檛 be ready and approved by this fall鈥檚 flu vaccination season.
Whether such new vaccines represent the next step in the fight against covid will be up to the FDA and the CDC.
Q: Are any entirely new variants on the horizon?
Experts agreed that the only newcomers in recent weeks have been incremental subvariants 鈥斅燾ertainly nothing that seems as game changing as delta or omicron were when they first appeared.
鈥淭here鈥檚 nothing we know of that鈥檚 lurking yet, and the surveillance is pretty darn aggressive,鈥 Schaffner said.
There are estimates that聽聽has been exposed to omicron and聽over 聽has received at least one dose of the vaccine, Gandhi said, 鈥渟o I am keeping my fingers crossed the development of new variants will slow with this degree of population immunity.鈥
Gandhi acknowledged some surprise at how quiet the horizon is right now, but she sees it as a positive development.聽
鈥淲e have now gone five months since hearing about a new variant, which I hope is reflective of increasing immunity in the world鈥檚 population,鈥 she said.