Omicron May Require Fourth Vaccine Dose, Pfizer Says

Carolyn Crist

December 09, 2021

Editor's note: Find the latest COVID-19 news and guidance in Medscape's Coronavirus Resource Center.

The new Omicron variant could make it more likely that people will need a fourth coronavirus vaccine earlier than expected, Pfizer officials said on Wednesday.

The standard two doses may be less effective against the variant, the company announced earlier in the day, and a booster dose increases neutralizing antibodies.

But the timeline might need to be moved up for a fourth dose. Previously, Pfizer CEO Albert Bourla, PhD, said another dose might be needed about a year after a third shot. Now the company's scientists believe that a fourth shot, which targets the Omicron variant, could be required sooner.

"With Omicron, we need to wait and see because we have very little information. We may need it faster," Bourla said on CNBC's Squawk Box.

"But for right now, the most important thing is that we have winter in front of us," he said. "From a healthcare perspective, it is important to understand that we need to be well-protected to go through the winter."

A third dose should provide protection throughout the winter, Bourla said. That may buy time until the early spring to develop new shots that target Omicron, which Pfizer could have ready by March, according to  Bloomberg News.

As of Wednesday afternoon, 43 people in 19 states had tested positive for the Omicron variant, according to The Associated Press. More than 75% had been vaccinated, and a third had had booster shots. About a third had traveled internationally.

Nearly all of them have had mild symptoms so far, the AP reported, with the most common symptoms being a cough, congestion, and fatigue. One person has been hospitalized, but no deaths have been reported so far.

The CDC is still trying to determine how the Omicron variant may affect the course of the pandemic and whether the strain is more contagious or causes more severe disease.

"What we generally know is the more mutations a variant has, the higher level you need your immunity to be," Rochelle Walensky, MD, director of the CDC, told the AP.

"We want to make sure we bolster everybody's immunity," she said. "And that's really what motivated the decision to expand our guidance [on boosters for all adults]."

The Omicron variant has been reported in 57 countries so far, World Health Organization officials reported on Wednesday, and they expect that number to continue growing.

"Certain features of Omicron, including its global spread and large number of mutations, suggest it could have a major impact on the course of the pandemic. Exactly what that impact will be is still difficult to know," Tedros Adhanom Ghebreyesus, PhD, the World Health Organization's director-general, said during a media briefing.

Several studies suggest that Omicron leads to a rapid increase in transmission, he said, though scientists are still trying to understand whether it can "outcompete Delta." Data from South Africa also suggests a higher risk of reinfection with Omicron, though it appears to cause milder disease than Delta, he noted.

"Even though we still need answers to some crucial questions, we are not defenseless against Omicron or Delta," he said. "The steps countries take today, and in the coming days and weeks, will determine how Omicron unfolds."

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