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July 1, 2022

Next Round of COVID Boosters Will Target Omicron

Next Round of COVID Boosters Will Target Omicron

Some Americans may be rolling up their sleeves for updated COVID booster shots this fall. Health officials monitoring the rise of new Omicron subvariants are attempting to do something they’ve not been able to achieve since the pandemic began: Stay one step ahead of the virus.

The U.S. Food and Drug Administration (FDA) has asked Pfizer and Moderna to tweak their Omicron-adapted COVID vaccines for the newest subvariants on the rise in the United States and other parts of the world. The move could help bolster protection ahead of an anticipated new wave of infections in the coming months. The FDA’s decision follows the 19-2 vote by its Vaccines and Related Biological Products Advisory Committee in favor of Omicron-specific boosters.

“As we move into the fall and winter, it is critical that we have safe and effective vaccine boosters that can provide protection against circulating and emerging variants to prevent the most severe consequences of COVID-19,” Peter Marks, M.D., Ph.D., director of the FDA’s Center for Biologics Evaluation and Research in a June 30 statement.

Why an updated booster is needed
Omicron has spawned two more subvariants, known as BA.4 and BA.5, that have been detected in dozens of countries around the world. Together, they are already responsible for nearly half of all new U.S. infections. Experts contend new cases may surge as summer gives way to fall—when temperatures drop, protection against COVID wanes, and more people head back indoors.

“That combination of waning immunity, combined with the potential emergence of novel variants during a time this winter when we will move inside as a population, increases our risk of a major COVID-19 outbreak and for that reason we have to give serious consideration to a booster campaign this fall to help protect us during this period from another COVID-19 surge,” Dr. Marks said during the FDA vaccine advisory committee meeting.

Omicron and its close cousins are less severe but more contagious than previous variants. They’re also more likely to successfully evade existing vaccines and treatments. Complicating matters, nearly three years of data shows that COVID immunity—from vaccination, infection, or both—wanes over time.

A February 2022 CDC study showed that vaccine effectiveness against COVID-related emergency room visits and hospitalizations was improved by a third dose but that protection fell over time. After four months, during the first Omicron wave, efficacy against urgent care visits fell from 87 percent to 66 percent and effectiveness against hospitalizations dropped from 91 percent to 78 percent.

Research suggests protection also wanes among those who have recovered from COVID. Another May 2022 CDC study found that vaccine protection against hospitalization among those who are re-infected fell to 68 percent after three doses. Efficacy against hospitalization fell to 35 percent among those who only received two doses of the vaccine.

So, while getting an initial booster improves protection against hospitalization, the original vaccines were designed to protect against the original COVID strain, which is no longer in circulation.

During the latest trials, the Omicron-specific boosters made by Pfizer and Moderna targeted both the original COVID strain as well as the first Omicron variant, known as BA.1. Data from both drug companies suggest their combination, or bivalent, vaccines trigger a stronger immune response against BA.1. Researchers noted the response was even greater than just another dose of the original vaccine.

Since the modified vaccines were formulated to target an older Omicron relative, they did not perform as well against BA.4 and BA.5—the Omicron variants that have since emerged. Still, the modified vaccines triggered a stronger immune response against these newer variants than the initial vaccine.

What happens next
Based on this data, the FDA advised both companies to update their modified vaccines so that they target BA.4 and BA.5—not BA.1. The hope is that by acting now, an updated booster may be ready by mid-fall.

“None of us has a crystal ball, and we are trying to use every last ounce of what we can from predictive modeling and from the data we have that’s emerging to try to get ahead of a virus that has been very crafty,” Marks said.

Regulatory officials have also asked Pfizer and Moderna to continue trials, including their updated BA.4 and BA.5 boosters. This trial data will be reviewed by the FDA before any possible authorization for emergency use in the United States.

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