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  • It could be 2 weeks or longer before we know with confidence how well the COVID-19 vaccines hold up against the Omicron variant.
  • Preliminary results from lab studies by Pfizer and BioNTech suggest that two doses of their vaccine may not be enough to protect against infection with Omicron, but three doses may boost that protection.
  • South African researchers reported that early data suggests the variant has a “substantial ability to evade immunity from prior infection.”
  • Scientists will also look at the spread of the variant in other countries, which have different vaccination rates and public health measures in place.

As the Omicron variant of the coronavirus continues to be transmitted throughout the world, one major question is how well the COVID-19 vaccines will hold up against it.

Results from lab studies that can help us answer this question are already starting to trickle in. Real-world data will follow over the next few weeks.

Preliminary antibody studies from Pfizer and BioNTech suggest that two doses of their vaccine may not be sufficient to protect against infection with the Omicron variant, the companies said December 8 in a news release.

However, they added that two doses may still provide protection against severe disease, because other aspects of the immune system are less affected by the mutations found in Omicron.

In addition, the studies showed that a third dose of the vaccine provided a similar level of neutralizing antibodies against Omicron as two doses did against the original strain of the coronavirus and other variants.

This is just one study and has not yet been peer-reviewed, so it should be viewed with caution.

Other preliminary studies have found a range of ways Omicron might impact the protection offered by COVID-19 vaccines.

As more results are released in the coming weeks — and reviewed by other scientists — we will gain a better picture of how well the vaccines protect against infection, severe disease, hospitalization, and death caused by the Omicron variant.

With Omicron, there are already signs that people who’ve already had COVID-19 may more easily develop reinfection.

South African researchers reported on Wednesday, Dec. 1, that real-world data from the country suggests the variant has a “substantial ability to evade immunity from prior infection.”

This kind of immune escape was not seen with the Beta and Delta variants during the country’s earlier surges.

However, South African researchers did not have information on the vaccination status of people with the Omicron variant, which limits what they can tell about the effectiveness of the vaccines.

“We… therefore cannot make any assessment of whether Omicron also evades vaccine-derived immunity,” study author Juliet Pulliam, PhD, who directs the South African Centre for Excellence in Epidemiological Modelling and Analysis at Stellenbosch University, said on Twitter.

The results were published on the preprint server medRxiv, so the study has not yet been peer-reviewed.

This is just one study, so it may not offer a complete picture of Omicron’s behavior, either.

Scientists will need to look at the spread of the variant in other countries, which have different vaccination rates and public health measures in place.

In addition, they will try to control for other factors that can increase a person’s chances of acquiring or developing severe illness, such as employment, other medical conditions, and living situation.

And they will look at which vaccines people received, whether they were fully vaccinated, if they received a booster, and how long it was since their last dose.

These studies will take time.

It will take even longer to see if there’s an increase in hospitalizations and deaths due to Omicron, as these lag behind cases by several weeks.

While both vaccination and infection can lead to immunity against the coronavirus, infection carries a risk of severe illness.

In the United States, people who are unvaccinated are 14 times more likely to die of COVID-19, compared with people who are fully vaccinated, according to data from the Centers for Disease Control and Prevention (CDC).

Some research also shows that the immune response from coronavirus infection varies greatly among people.

And, like the antibody protection offered by vaccines, infection-acquired immunity wanes over time.

In addition to real-world studies, scientists will test how well antibodies in the blood of people who’ve been vaccinated can fend off Omicron.

These tests are done in a laboratory. In particular, scientists look at the neutralizing activity of the antibodies against the variant.

Neutralizing antibodies can tightly bind to the virus and effectively neutralize it, such as by preventing it from infecting cells.

If the neutralizing activity drops too low in the face of Omicron, this could indicate that the vaccines are less effective against this variant.

The vaccines approved in the United States target the spike protein of the coronavirus. Omicron has dozens of mutations, with as many as 32 in its spike protein.

We already know about some of these mutations because they have been identified in previous variants.

“We have some clues that we may have some reduced efficacy of vaccines [against Omicron]. But we don’t have that information yet,” Maria Van Kerkhove, PhD, World Health Organization technical lead on COVID-19, said Friday, Dec. 3, in a public briefing.

“It will take a week or two — or three — to get that [information]. We need scientists to have a little bit more time before we have that answer,” Kerkhove said.

One challenge with testing the level of neutralizing antibodies is figuring out what it means for the real world. There’s not a clear point at which the antibody level drops from good to bad.

Of course, a bigger drop in neutralizing antibodies is worse.

But how far does the level have to fall for a person’s risk of infection to increase by a certain amount? Or for their risk of severe illness to become worrisome?

Scientists are working to figure out the answers to these questions — not just for Omicron, but also for Delta.

Even if there’s a drop in neutralizing activity against Omicron, the immune system has other ways to protect against the coronavirus.

After vaccination, people also generate other types of antibodies, as well as B cells and T cells. These other layers can kick in even with a drop in neutralizing antibodies.

Scientists will measure the level of T cells and antibody-generating B cells in people who have been vaccinated, looking for ones that target Omicron effectively. These studies, though, are more complicated and can take longer to carry out.

Many experts believe that people who are fully vaccinated will still be well-protected against severe illness caused by Omicron, even if they’re more likely to develop an infection — or reinfection — than with earlier variants.

“A lot of those mutations [found in Omicron] are associated with immune escape. But I think it’s still very possible that the vaccines will hold up against severe disease, even with those mutations,” Dr. Carlos del Rio, a professor of medicine at Emory University School of Medicine, said Dec. 2 in a media briefing of the Infectious Diseases Society of America (IDSA).

“At this point in time, we need to follow the science… and we’ll get more information in the next couple of weeks,” del Rio said.

It’s also too early to know yet if we will need an Omicron-specific vaccine or booster.

Vaccine makers reportedly say they can develop a new vaccine within months, but they may wait to see how much of a problem Omicron becomes before rolling them out.

The Beta variant showed signs that it could overcome some of the protection offered by vaccines, but the variant didn’t spread much beyond South Africa, where it was first detected.

Also, Delta is still the predominant variant in the United States and many other parts of the world, and is driving an increase in cases and hospitalizations in some areas.

“Probably the most important thing for people to do is to make sure that they get their COVID vaccine, because we know that’s protective against Delta,” said Dr. Ashley Lipps, an infectious disease expert at The Ohio State University Wexner Medical Center.

Research also suggests that boosters of the current vaccine should help people better fend off Omicron, even if there’s a drop in the level of neutralizing antibodies.

“There’s every reason to believe, as we talk about boosters, when you get a level [of antibodies] high enough, that you are going to get at least some degree of cross-protection [against Omicron], particularly against severe disease,” Dr. Anthony Fauci, the country’s top infectious disease official, said at a briefing on Nov. 30.

Experts also emphasize that we already have other tools that have worked against all the previous versions of the coronavirus: face masks, better ventilation indoors, physical distancing, testing, and contact tracing.

“We’ve heard these things so many times, but they really do work,” Dr. Julie Vaishampayan, public health officer for Stanislaus County, California, said at the IDSA briefing.