Virologist explains the science of immune protection against ‘stealth omicron’

Cases of COVID-19 are steadily trending down in King County (the public health department reports 3,574 daily average cases as of Jan. 24, down from a peak of 6,442 on Jan. 10). And last week, Gov. Jay Inslee — along with University of Washington Medicine — nodded at the possibility of the pandemic reaching a stage of endemicity, or the point at which COVID’s spread is predictable and manageable.

That said, vaccines will continue to be the most important tool to mitigate future COVID outbreaks, says Dr. Angela Rasmussen, virologist with the Vaccine and Infectious Disease Organization.

“A lot of people have been saying ‘fully vaccinated people can get omicron, so what’s the point?’” Rasmussen told KIRO Newsradio’s Gee Scott and Ursula Reutin Show.

“Well, the point is that, first of all, boosting for other vaccines, as well as for COVID vaccines, really does help lock in that long-term immune protection,” she said. “There’s increasingly a lot of data that shows that while a booster shot can’t completely protect you against getting infected with omicron, it does significantly reduce the likelihood that you will be infected at all.”

Rasmussen contextualized that idea of long=term protection within the concern that most COVID vaccines are designed to target an aspect of the virus that has mutated with BA.1 (omicron) and BA.2 —  the latter of which has been dubbed “stealth omicron,” a term that refers to PCR tests’ difficulty in differentiating among mutated iterations of coronavirus.

“The issue with omicron is that omicron’s spike protein, which is what the vaccines are targeting, is pretty different,” Rasmussen continued. “It’s different biochemically. It’s actually a different chemical shape, if you will, that the antibodies the vaccine elicited might not recognize, so they might not appreciate that omicron is in fact SARS-CoV-2, because of those mutations in the spike protein.”

The virologist addressed why, despite that difficulty of recognition, COVID vaccines and booster doses are useful in preventing infection, severe infection, hospitalization, and transmission.

“Those antibodies aren’t going to be as effective at preventing an infection altogether,” Rasmussen noted. “But there is quite a lot of data now, and this has been consistent throughout the pandemic with all of the variants, that the vaccines, and actually prior infection as well, induce a pretty robust cross protective T cell response.”

Rasmussen differentiated antibody B cells from T cells in that the latter are responsible for the immune system’s coordinated response against active infection.

“Even if you do get a breakthrough infection, if you’ve been vaccinated, you have T cells that are essentially ready to go, killing the infected cells. That means those infected cells can’t make new virus, what we call progeny virus,” she explained. “That means that if you are vaccinated, you will not be shedding as much virus. That means you’re much less likely to transmit it to somebody else.”

“It also means that your infection will be cleared more quickly, which means that likely you’ll be less sick than you would have been if you weren’t protected with vaccination.”

Rasmussen clarified why vaccines are useful even for those who have already contracted COVID.

“Some people do mount immune responses that are relatively equivalent to the immune responses that are elicited by the vaccine after infection. But not everybody does,” she said. “Some people also have immune responses that really aren’t protective at all, or that don’t last very long after infection — it’s just much more variable. We know that getting a vaccine on top of a prior infection really does give you the best immunity.”

Dr. Rasmussen is a virologist and has a PhD in microbiology and immunology from Columbia University that she got in 2009. She did her postdoc at the University of Washington. Now, Rasmussen studies emerging viruses, including SARS-CoV-2, and is an associate professor at the University of Saskatchewan, working at the Vaccine and Infectious Disease Organization, which is a research institute that focuses on developing vaccines for pandemic viruses.

Listen to the Gee Scott and Ursula Reutin Show weekday mornings from 9 a.m. – 12 p.m. on KIRO Newsradio, 97.3 FM. Subscribe to the podcast here.