How severe is omicron? Your COVID-19 questions answered

The new omicron variant of COVID-19 has only been on the world’s radar for about a month, and much remains unknown about it — though what scientists have learned is less than reassuring.

Omicron is significantly more contagious than the delta variant, which is still causing the majority of COVID-19 cases in Colorado. Dr. Tom Frieden, former head of the Centers for Disease Control and Prevention, compared it to measles, which is one of the most contagious viruses humans have had the misfortune to encounter.

It’s also harder for the immune system to recognize and stop, meaning people who’ve been vaccinated are more likely to have a breakthrough case and those who’ve been infected by a previous version of the virus face a higher risk of reinfection. And it’s rapidly replacing delta, driving a spike in cases across the country.

Omicron accounted for only about one in 10 COVID-19 infections in Colorado as of the week of Dec. 12 — the last week with full data — but state officials have started preparing for what looks like its inevitable takeover. Gov. Jared Polis announced Tuesday that the state would redirect treatments with a better chance of working against omicron to counties where the variant is more widespread, and would open more mass sites for COVID-19 testing and vaccination.

The Denver Post put together this guide to what we do and don’t know about omicron.

Is it less severe?

This is the biggest unanswered question.

In South Africa, patients were less likely to be hospitalized with omicron, and those who were hospitalized tended to recover faster. It’s not clear if that will be the situation everywhere, though, because the people who were infected in South Africa were generally young, and scientists believe that almost all of the country’s residents were exposed to a previous version of the virus, based on sky-high deaths there.

When the immune system has gotten a preview of the virus’ spike, whether through vaccination or prior infection, it has a head start at fighting back against the virus, reducing the odds of serious illness. (Unlike an infection, the vaccine introduces only the spike, which primes the immune system but can’t cause disease.) That means you’d expect fewer severe illnesses in South Africa now, regardless of omicron’s characteristics.

We’ll have to wait for a definitive answer on this one.

Will the vaccines still work?

So far, they’re holding up in terms of preventing severe illnesses and deaths, reducing the odds by about 70% compared to unvaccinated people. But protection against mild illness is down considerably.

Early data from the United Kingdom suggests having two doses of the Pfizer vaccine or a prior infection also won’t offer much protection, with either reducing the risk of a new infection by about 20%. People who’d had a booster dose had more protection, with estimates ranging from 55% to 80%.

The Moderna and Johnson & Johnson shots weren’t used in the United Kingdom, so there’s little evidence on how they’re performing. Generally, the Moderna and Pfizer shots have posted similar results, with the Johnson & Johnson shot showing slightly lower effectiveness.

The problem is that antibodies to previous versions of the virus have a harder time “sticking” to omicron’s mutated spike and stopping it from entering cells, Dr. Celine Gounder, an infectious disease specialist at New York University, said on a webinar for journalists. Increasing the number of antibodies by getting a third shot helps, but even people who’ve had a booster should expect more breakthrough cases, she said.

Cases among vaccinated people should be milder, though, because the immune system has other lines of defense, Gounder said. It takes a few days for the body to muster those, allowing the virus to establish a foothold, but probably not enough to make you seriously sick, she said.

“It’s not going to be possible to prevent all infections with vaccines,” she said. “I think the outcome of interest should be severe illness, hospitalization and death.”

What about our other tools?

Other than vaccines, the most important layer of protection for people at high risk of severe disease is access to monoclonal antibody treatment if they get infected.

Monoclonal antibodies are lab-created versions of the substances the immune system produces to disable the virus and prevent it from entering cells. Unfortunately, two of the three monoclonal antibody options don’t work well against omicron, and there isn’t enough of the third to treat all of the high-risk people expected to become sick in the next few weeks.

Pfizer’s new antiviral pill, Paxlovid, is expected to work against omicron, but it’s not yet available.

How bad could it get?

It’s always difficult to forecast what COVID-19 is going to do next. That said, scientists are worried. Dr. Anthony Fauci, the nation’s top infectious disease specialist, warned on Sunday that cases could reach record highs in January.

Even if omicron is milder and the risk to any individual is lower, the health care system could be in trouble, Gounder said. If a massive number of people are infected and a small percentage of them become seriously ill, that still could mean more patients than hospitals can handle, she said.

It’s a good idea for everyone to take multiple steps to protect themselves, like wearing masks and moving their gatherings outdoors, but it’s vital for unvaccinated people, older people and those who have medical conditions that put them at high risk, Gounder said.

“We anticipate an increase in hospitalizations and an increase in deaths in the next few weeks,” she said.

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