This photo provided by Pfizer shows vials of the company's...

This photo provided by Pfizer shows vials of the company's updated COVID-19 vaccine during production in Kalamazoo, Michigan.  Credit: AP

As the nation prepares for another potential wave of COVID-19 infections this fall and winter, the Food and Drug Administration on Wednesday approved booster vaccines that target the most prevalent omicron virus strains.

The FDA's approval of the Pfizer and Moderna "bivalent" shots — combination doses that contain half the original vaccine recipe and half protection against the BA.4 and BA.5 subvariants — is the first significant modification to the COVID-19 mRNA vaccine.

The highly contagious subvariants are the source of nearly all new infections and are expected to spread rapidly in the coming months as more Americans move activities indoors during the colder weather.

"The prior mRNA vaccines were targeted against the original strains of the COVID-19 virus, and, as we've seen, have had diminishing impact in the era of the omicron variants," said Matthew Harris, medical director of the Northwell Health vaccination program. "So this is really an exciting moment to move forward. And I think it's going to be an important part of the next few months in the ongoing fight against the pandemic."

WHAT TO KNOW

  • The Food and Drug Administration Wednesday approved a modified “bivalent” booster shot that combines the half the original vaccine strain and half specific protection against the highly contagious BA. 4 and BA. 5 omicron strains.
  • Doses by Pfizer are for anyone 12 and older while Moderna is for those 18 and older. Individuals must have received their original vaccination series and be at least two months from their last primary vaccination or booster.
  • The final approval step could come Thursday when a Centers for Disease Control and Prevention panel meets to decide who should get the shot and if high-risk individuals should be at the front of the line.

The hope, Harris said, is for the new booster to not only protect patients with COVID-19 from severe illness and hospitalization but to also reduce the number of breakthrough infections among those who are vaccinated and boosted. 

As a single dose, Moderna’s bivalent vaccine is authorized for those 18 and older while Pfizer’s two-dose regimen is for those ages 12 and above.

The updated boosters can be taken at least two months after an individual has received their last primary vaccination or booster, the FDA said. Individuals must have received their primary vaccinations, using the original vaccines, to be eligible for the bivalent booster. The original booster formulation will no longer be authorized, officials said.

"As we head into fall and begin to spend more time indoors, we strongly encourage anyone who is eligible to consider receiving a booster dose with a bivalent COVID-19 vaccine to provide better protection against currently circulating variants," FDA Commissioner Dr. Robert Califf said in a statement.

But first, the Centers for Disease Control and Prevention must formally recommend who should get the additional shot. A CDC advisory panel will debate the evidence on Thursday, including whether Americans at high risk from COVID-19 should be first in line. If approved by the CDC, distribution of the shots could begin in the coming days.

The United States has purchased more than 170 million doses from the two companies, officials said. Pfizer said it could ship up to 15 million of those doses by the end of next week.

Approval of the booster comes as students return to classrooms on Long Island this week, where infections remain stubbornly around 8%, even during the warm weather months.

The looming question, experts said, is whether vaccine-weary New Yorkers will roll up their sleeves again. Roughly half of vaccinated Americans received the first recommended booster dose, and only a third of those 50 and older who were urged to get a second booster followed that recommendation, data shows.

Dr. Aaron Glatt, chairman of medicine and chief of infectious diseases at Mount Sinai South Nassau Hospital in Oceanside, said recommendations on the new booster should be based on the individual.

For example, Glatt said he would recommend the booster for an obese 95-year-old man with only one previous booster. But a healthy 27-year-old who had his second booster two months ago and had COVID-19 a few months earlier may not be the best candidate, he said.

"This is where we have the luxury of not being in a crisis situation," Glatt said "When we first came out with these vaccines, there was a crisis and you really wanted to get everybody vaccinated as fast as possible. With these boosters, we want to vaccinate as fast as possible those people that would benefit from it the most."

The process for FDA approval of the new boosters was a departure from the previous vaccines, which relied on lengthy clinical human trials.

Instead, this authorization relies largely on trial data collected from testing the safety and immune response triggered by the new shots in animals, as well as data from other formulations previously studied by the vaccine makers — an approach that resembles approval of the annual influenza vaccine. Nonetheless, the two vaccine makers are still planning to complete human clinical trials of the new shots.

 “We have worked closely with the vaccine manufacturers to ensure the development of these updated boosters was done safely and efficiently," said FDA vaccine chief Dr. Peter Marks. "The FDA has extensive experience with strain changes for annual influenza vaccines. … The public can be assured that a great deal of care has been taken by the FDA to ensure that these bivalent COVID-19 vaccines meet our rigorous safety, effectiveness and manufacturing quality standards for emergency use authorization."

With AP 

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