A fourth vaccine dose doesn't seem to fully stop omicron, study finds

Omicron's vaccine-resistant properties have prompted Pfizer to start work on an omicron-specific vaccine

By Matthew Rozsa

Published January 18, 2022 3:00PM (EST)

A medical assistant prepares syringes with the Pfizer/BioNTech vaccine against Covid-19 at the Humboldt Forum museum during the Omicron wave of the coronavirus pandemic on January 18, 2022 in Berlin, Germany. (Sean Gallup/Getty Images)
A medical assistant prepares syringes with the Pfizer/BioNTech vaccine against Covid-19 at the Humboldt Forum museum during the Omicron wave of the coronavirus pandemic on January 18, 2022 in Berlin, Germany. (Sean Gallup/Getty Images)

Besides being incredibly contagious, COVID-19's omicron variant is frightening for its vaccine-resistant properties. The novel strain has more mutations around a crucial group of proteins that were used to create the original mRNA vaccines. Because of this, said vaccines are not as adept at protecting against the omicron strain, meaning breakthrough infections are common.

But as far as public health officials and immunologists are concerned, no infection at all would be preferable to even a mild breakthrough case — as such cases mean the virus can and will continue to spread. 

Hence, two weeks ago, a group of Israeli scientists studied whether the existing Pfizer-BioNTech vaccine can protect against omicron infections if patients are given four doses of vaccine, meaning a two-shot vaccine and two boosters. 

Now, they have an early answer: The booster shot helps somewhat, but not enough to prevent infections. The findings speak to the unique and squirrelly nature of the omicron variant. 

Preliminary data from the clinical trial, which included 154 medical personnel at Tel Aviv's Sheba Medical Center, revealed that those who received four doses of the vaccine had higher antibody levels than those who did not. While this regimen partially defended patients against omicron, the same vaccines that were effective against other mutant SARS-CoV-2 viruses proved weaker when confronted with omicron.

The good news was that the fully vaccinated patients infected with omicron reported either mild symptoms or none at all. This is consistent with previous studies which have found that omicron is not as deadly as other strains and that fully vaccinated people are still much safer from COVID-19 — both in terms of getting the disease and in terms of developing severe symptoms — than those who are not.

This is not the end of the Israeli research. Sheba researchers are also currently testing the efficacy of a fourth dose of the Moderna vaccine, which like the Pfizer-BioNTech inoculation utilizes mRNA technology. In addition, the Israeli government has already made fourth doses of vaccines available to people who are elderly or immunocompromised.

RELATED: Omicron's lower mortality rate may be explained by how the variant spreads through the body

It is unclear whether the United States will also start offering fourth doses. Some public health experts, including those at the European Union, have warned that receiving too many COVID-19 vaccines could weaken a patient's immune system. In addition, policymakers have to consider our limited resources.

"You have to then ask yourself, 'What is the goal?'" L.J Tan, chief strategy officer for the Immunization Action Coalition, told Salon in December. Tan observed that policymakers should try to get initial booster shots to everyone if their goal is to "reduce hospitalizations, reduce the surge on the systems, and reduce the number of people getting severely ill." At the same time, he added that "if the goal is to stop transmission and stop people from passing omicron from one person to another, then perhaps a fourth dose is necessary."


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Albert Bourla, the CEO of Pfizer, told CNBC's "Squawk Box" last week that his company is already working on a vaccine specific to the omicron variant and it hopes to release it within the coming months.

"This vaccine will be ready in March," Bourla explained. "We [are] already starting manufacturing some of these quantities at risk."

He added that the vaccine will also try to target other mutant variants, as it is unclear whether an omicron vaccine is necessary at this point. At the same time, Bourla said that Pfizer will have some doses ready for those countries that say they want them as soon as possible.

"The hope is that we will achieve something that will have way, way better protection particularly against infections, because the protection against the hospitalizations and the severe disease — it is reasonable right now, with the current vaccines as long as you are having let's say the third dose," Bourla told CNBC.

It may not be realistic for pharmaceutical companies to produce inoculations for all of the COVID-19 variants that arise. Because it takes four to six months from the moment a company learns of a variant to when it could have batches of bespoke vaccines ready for distribution, business leaders are wary of creating a vaccine for a bug that may no longer be a problem by the time the shots are ready. This is what happened with the beta variant, which peaked and subsided in two months, although the omicron variant presents unique challenges of its own.

While other SARS-CoV-2 viruses can be traced back to the ancestral virus that originated in Wuhan, China, omicron has mysterious origins. All of the existing vaccines were designed to protect against the original version of the virus.

Read more on omicron's rise:


Matthew Rozsa

Matthew Rozsa is a staff writer for Salon. He holds an MA in History from Rutgers University-Newark and is ABD in his PhD program in History at Lehigh University. His work has appeared in Mic, Quartz and MSNBC.

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