COVID-19 Boosters Are Being Updated To Target Omicron Subvariants—Here's Why

A new round of COVID-19 boosters is on the way that have been specially formulated to target and fight the extremely contagious omicron subvariants BA.4 and BA.5.

In late June, the US Food and Drugs Administration (FDA) announced that it was advising vaccine manufacturers to create reformulated vaccines.

"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, MD, PhD, director of the FDA's Center for Biologics Evaluation and Research, said in an FDA press release issued at the time.

The boosters will be available as early as fall and are expected to provide protection against a surge of coronavirus cases that's likely to occur through fall and winter. Here's a closer look at everything you need to know about the new booster shots.

What Spurred the FDA's decision?

The FDA's decision to alter the formulation of upcoming boosters is based on the high level of infectiousness of BA.4 and BA.5 and their resistance to neutralizing antibodies. Both the BA.4 and BA.5 subvariants can infect and reinfect anyone, regardless of prior immunity. Antibodies gained after recovering from Omicron don't seem protect against the new subvariants.

As of July, Omicron BA.4 and BA.5 are the dominant subvariants in the United States. Both made up just 1% of coronavirus infections at the beginning of May, but new data from the Centers for Disease Control and Prevention (CDC) shows that combined, the pair now accounts for well more than 70% of recent cases as of July.

Research suggests the BA.4 and BA.5 subvariants are also more resistant to antibodies from people who were triple-vaccinated with either the AstraZeneca or Pfizer-BioNTech vaccines. Both subvariants share a specific mutation in the spike protein that allows them to evade detection from different classes of antibodies.

"The problem we have with Omicron variants is that it's a smarter virus. The antibodies that you made for Omicron way back in December don't function very well to protect you," Sharon Nachman, MD, the division chief of pediatric infectious disease at Stony Brook Medicine, told Health

Adding components from two different ‌Omicron subvariants, as the FDA has directed, creates what's known as a bivalent booster. Adding more Omicron strains should ideally increase a person's immunity against a potentially deadly infection.

"The FDA directive regarding a bivalent booster is a nod to the fact that we are seeing Omicron become more antibody evasive," explained Susan Hassig, DrPH, MPH, an associate professor and director of epidemiology at Tulane University. "If Omicron continues to mutate and generate additional strains, then inserting a BA.4 and BA.5 antigen for the fall boosters would provide a little more training to the immune system that might provide a more effective antibody response for individuals that subsequently become exposed."

While antibodies from vaccines also provide limited protection, they may provide better protection than the antibodies produced by your body after infection. This is because vaccines produce more antibodies that are longer lasting.

"It's not a perfect match, because of the new spike protein that Omicron BA.5 variants have, but it will work reasonably well as opposed to antibodies you made back in December that were made in small amounts," explained Dr. Nachman.

What Happens Next?

The FDA panel voted to redesign the next round of COVID-19 booster shots to include the Omicron BA.4 and BA.5 spike protein into the vaccine ingredient list. The booster would create antibodies that target and detect Omicron BA.4 and BA.5.

Several vaccine manufacturers were already testing boosters targeting the BA.1 Omicron strain. However, these boosters and the associated test data is already out of date as BA.4 and BA.5 have taken over as dominant viral strains.

Once manufacturers adjust their vaccines to include components of BA.4 and BA.5, they will need to redo their clinical trials to test the modified vaccine's safety and effectiveness against coronavirus infections.

The FDA's vote is focused solely on changes to the upcoming boosters scheduled to be available in the fall. It does not affect the vaccines currently being used for primary immunization.

How Long Will Reformulated Boosters Be Effective?

Over the course of two years, the virus has mutated rapidly, making it hard to predict which strains will become highly infectious and or most severe. With that said, experts are concerned that by the time vaccine manufacturers make and distribute the new bivalent vaccines, we could be dealing with yet another new SARS-CoV-2 variant that may—or may not—be Omicron.

"One of the challenges of creating COVID-19 boosters is that it takes only 8 to 10 weeks for a new mutation to emerge," said Dr. Hassig. "There's no manufacturing process that can keep up with that."

Updating and reformulating boosters and vaccines is one approach to addressing the mutations. But a more effective and long-lasting solution might include developing a universal coronavirus vaccine that targets regions of the virus that do not mutate as much.

"The holy grail would be to make an agnostic vaccine that doesn't care about multiple variants. We would develop a vaccine that makes antibodies to the nonvariable region, but it's still protective against people getting that virus attached to their cells," Dr. Nachman said.

Pfizer and BioNTech are taking steps in that direction including testing a universal coronavirus vaccine. But until a universal coronavirus vaccine become available, the best bet for protection is the upcoming bivalent boosters.

"The bivalent booster will expand the array of immune protection that people get from vaccines and that's good because the virus keeps changing," said Dr. Hassig.