Since bursting onto the world stage in 2020, COVID-19 has attacked the immune systems of hundreds of millions of people. Thanks to its constant mutations, the virus has been able to infect millions more, years after the start of the pandemic. 

The alpha, beta and delta variants of coronavirus were each responsible for case surges in 2021, until omicron took over as the dominant variant. Now, a subvariant of omicron nicknamed “nimbus” may lead to a summer spike in cases due to its increased transmissibility, said Chief Campus Health Officer Dr. Sarah Van Orman in a briefing with campus media Monday.   

At the start of May, the nimbus variant made up only about 5% of all cases in the United States. By early June, the Centers for Disease Control and Prevention estimated that number had climbed to 43%. So far in 2025, more than 12,600 people in the U.S. have died from COVID-19.

The nimbus variant appears to be causing more throat symptoms compared to other variants and media outlets, including the Los Angeles Times, have dubbed it the “razor blade throat” variant. Despite that nickname, Van Orman said nimbus does not seem to be causing an uptick in hospitalizations or deaths.

While the CDC guidelines state that individuals who’ve contracted COVID-19 may resume daily activities once they have been fever-free for 24 hours, Van Orman recommends waiting 24 hours after “feeling better,” instead. 

Van Orman said people who test positive for COVID-19 should wear a mask for five days when around others, and these recommendations remain the same for everyone, regardless of vaccination status.  

The exact herd immunity threshold — when enough of a population is immune to a disease that its ability to spread is seriously hindered — varies based on each virus and how effective vaccines are. 

While the exact percentage of the population needed to achieve durable immunity against COVID-19 is still not definitively known, according to Rochester Regional Health, the fact that the coronavirus mutates so rapidly makes achieving herd immunity challenging. 

“[Coronavirus] is a remarkably nimble virus that keeps evolving,” Van Orman said. “The more something changes, the more people become susceptible. … It’s quite a little slippery virus.”

In a video posted to social media on May 27, U.S. Health and Human Services Secretary Robert F. Kennedy Jr. announced that the CDC is no longer recommending COVID-19 annual booster shots for healthy children and pregnant women.

“Last year, the Biden administration urged healthy children to get yet another COVID shot, despite the lack of any clinical data to support the repeat booster strategy in children,” Kennedy said in the video. 

The CDC’s child and adolescent immunization schedule now reads “see notes” for the COVID-19 vaccine, linking to a paragraph that emphasizes “shared clinical decision-making” between the healthcare provider, the patient and the parent or guardian” for ages six months to 17-years-old.

Van Orman said the COVID-19 vaccines remain safe and effective at preventing severe illness and hospitalizations. She said it is especially important for those at high risk — including people who are older, pregnant or have underlying conditions — to get the vaccine. 

“There’s no reason why anyone should not receive the vaccine unless they’re one of a rare handful of people who might have had an allergic reaction to the vaccine,” Van Orman said. “I’m not sure what [the Department of Health and Human Services is] using to make those decisions, but based on my understanding of the virus, my understanding of the literature, that’s what I would recommend.”

To stay protected, Van Orman recommended washing hands frequently, wearing a mask in crowded areas and getting a COVID-19 booster approved by the Food and Drug Administration this fall once it becomes available.