The U.S. is urging that everyone 12 and older get a COVID-19 booster as soon as they're eligible, to help fight back the hugely contagious omicron mutant that's ripping through the country.

Boosters already were encouraged for all Americans 16 and older, but Wednesday the Centers for Disease Control and Prevention endorsed an extra Pfizer shot for younger teens — those 12 to 15 — and strengthened its recommendation that 16- and 17-year-olds get it, too.

"It is critical that we protect our children and teens from COVID-19 infection and the complications of severe disease," Dr. Rochelle Walensky, the CDC's director, said in a statement Wednesday night.

"This booster dose will provide optimized protection against COVID-19 and the Omicron variant. I encourage all parents to keep their children up to date with CDC's COVID-19 vaccine recommendations," she said.

Vaccines still offer strong protection against serious illness from any type of COVID-19, including omicron — what experts say is their most important benefit. But the newest mutant can slip past a layer of the vaccines' protection to cause milder infections. Studies show a booster dose at least temporarily revs up virus-fighting antibodies to levels that offer the best chance at avoiding symptomatic infection, even from omicron.

Earlier Wednesday, the CDC's independent scientific advisers wrestled with whether a booster should be an option for younger teens, who tend not to get as sick from COVID-19 as adults, or more strongly recommended.

Giving teens a booster for a temporary jump in protection against infections is like playing whack-a-mole, cautioned CDC adviser Dr. Sarah Long of Drexel University. But she said the extra shot was worth it to help push back the omicron mutant and shield kids from the missed school and other problems that come with even a very mild case of COVID-19.

More important, if a child with a mild infection spreads it to a more vulnerable parent or grandparent who then dies, the impact "is absolutely crushing," said panelist Dr. Camille Kotton of Massachusetts General Hospital.

"Let's whack this one down," agreed Dr. Jamie Loehr of Cayuga Family Medicine in Ithaca, New York.

The vaccine made by Pfizer and its partner BioNTech is the only option for American children of any age. The CDC says about 13.5 million children ages 12 to 17 — slightly more than half of that age group — have received two Pfizer shots. Boosters were opened to the 16- and 17-year-olds last month.

Wednesday's decision means about 5 million of the younger teens who had their last shot in the spring are eligible for a booster right away. New U.S. guidelines say anyone who received two Pfizer vaccinations and is eligible for a booster can get it five months after their last shot, rather than the six months previously recommended.

But one committee member, Dr. Helen Keipp Talbot of Vanderbilt University, worried that such a strong recommendation for teen boosters would distract from getting shots into the arms of kids who have not been vaccinated at all.

The advisers saw U.S. data making clear that symptomatic COVID-19 cases and hospitalizations are between seven and 11 times higher in unvaccinated adolescents than vaccinated ones.

While children do tend to suffer less serious illness from COVID-19 than adults, child hospitalizations are rising during the omicron wave — the vast majority of them unvaccinated.

During the public comment part of Wednesday's meeting, Dr. Julie Boom of Texas Children's Hospital said a booster recommendation for younger teens "cannot come soon enough."

The chief safety question for adolescents is a rare side effect called myocarditis, a type of heart inflammation seen mostly in younger men and teen boys who get either the Pfizer or Moderna vaccines. The vast majority of cases are mild — far milder than the heart inflammation COVID-19 can cause — and they seem to peak in older teens, those 16 and 17.

The FDA decided a booster dose was as safe for the younger teens as the older ones based largely on data from 6,300 12- to 15-year-olds in Israel who got a Pfizer booster five months after their second dose. Israeli officials said Wednesday that they've seen two cases of mild myocarditis in this age group after giving more boosters, 40,000.

Earlier this week, FDA vaccine chief Dr. Peter Marks said the side effect occurs in about 1 in 10,000 men and boys ages 16 to 30 after their second shot. But he said a third dose appears less risky, by about a third, probably because more time has passed before the booster than between the first two shots.

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A key Centers for Disease Control and Prevention panel is meeting Wednesday and will likely take a vote on whether to issue emergency approval for COVID-19 vaccine booster shots for adolescents as young as 12.

The CDC's Advisory Committee on Immunization Practices meeting will likely end in a vote on whether to issue an approval for Pfizer's booster for use among people aged 12 to 15 years old.

The Food and Drug Administration issued its own approval for the booster shots earlier this week. Should the ACIP vote to approve the boosters, CDC Director Dr. Rochelle Walensky will need to issue a formal recommendation to make the shots available for adolescents.

Pfizer's COVID-19 vaccine was approved for use in adolescents in May, and the CDC has recommended adults seek a booster shot five months after their final dose. That means that many teens will immediately be eligible for additional shots as soon as they are available.

The move comes as the U.S. deals with a surge in COVID-19 cases caused by the highly contagious omicron variant. While the new strain has shown to be slightly more resistant to vaccines, health officials say vaccines and booster shots offer significant protection against severe disease and death.

The Food and Drug Administration will likely authorize Pfizer's COVID-19 booster shot for adolescents aged 12 to 15 by next week, The Washington Post and The New York Times reported on Thursday.

The Pfizer vaccine would be the first booster shot to receive emergency authorization for young teens and pre-teens.

Pfizer's COVID-19 vaccine was approved for use in adolescents in May, and the CDC has recommended adults seek a booster shot six months after their final dose. Should that recommendation carry over to adolescents, many would be eligible for a booster immediately upon approval.

The impending decision comes as the U.S. deals with a surge in COVID-19 cases caused by the highly contagious omicron variant. While the new strain has shown to be slightly more resistant to vaccines, health officials say vaccines and booster shots offer significant protection against severe disease and death.

Dr. Rochelle Walensky, director of the Centers for Disease Control, signed off on a recommendation to expand eligibility for the Moderna and Pfizer COVID-19 booster shots.

Walensky's decision came after the vote of approval from a key CDC advisory panel.

"Booster shots have demonstrated the ability to safely increase people’s protection against infection and severe outcomes and are an important public health tool to strengthen our defenses against the virus as we enter the winter holidays. Based on the compelling evidence, all adults over 18 should now have equitable access to a COVID-19 booster dose," Walensky said.

Earlier in the day, the FDA approved Moderna's and Pfizer's boosters for all U.S. adults who completed their first series of vaccines six months prior.

Previously, the FDA and the CDC approved booster shots of the Pfizer, Moderna and Johnson & Johnson vaccines for people aged 65 and up, people who have underlying health conditions that make them susceptible to the virus and those who are at an increased risk of contracting the virus because of their job or living situation. At the same time, regulators approved the mixing and matching of vaccine brands when it comes to booster shots.

The CDC reports that more than 32 million Americans have already gotten a COVID-19 vaccine booster shot. However, the agency says 47 million Americans are still not vaccinated.

Johnson & Johnson said Wednesday that new data from early trials of a booster shot of its COVID-19 vaccine provides a "rapid and robust increase in spike-binding antibodies" that fight off the virus.

In a press release, the company noted that the antibody response provided by the single-shot vaccine was "strong and stable" eight months later. However, eyes are turning to booster shots as widespread vaccine use nears the one-year mark.

In its press release, Johnson & Johnson noted that a person who gets a booster shot saw a nine-fold increase in antibodies when compared to antibody response 28 days after an initial dose.

"With these new data, we also see that a booster dose of the Johnson & Johnson COVID-19 vaccine further increases antibody responses among study participants who had previously received our vaccine," said Dr. Mathai Mammen, the global head of Janssen Research & Development, Johnson & Johnson. "We look forward to discussing with public health officials a potential strategy for our Johnson & Johnson COVID-19 vaccine, boosting eight months or longer after the primary single-dose vaccination."

Earlier this month, top federal health officials recommended that Americans seek out a COVID-19 booster shot eight months after full vaccination. The booster shot program is slated to begin Sept. 20, pending approval from the Food & Drug Administration and the Centers for Disease Control and Prevention.

In issuing a recommendation for booster shots, officials said that while all COVID-19 vaccines remain extremely effective in preventing instances of severe infection or death from the virus, there has been some data to show that those vaccinated are more susceptible to mild cases of the virus eight months after vaccination. They've also seen evidence that those vaccinated are more susceptible to unknowingly spreading the virus as time goes on.

The Johnson & Johnson vaccine was granted emergency use authorization in late February, meaning booster shots for those who received the J&J vaccine would be available in late October if the FDA and the CDC ultimately approve them.

The Johnson & Johnson vaccine still only has emergency use approval from the FDA. Earlier this week, the agency granted full approval to the Pfizer vaccine — the first COVID-19 vaccine to receive such a designation.

U.S. health officials Wednesday recommended all Americans get COVID-19 booster shots to shore up their protection amid the surging delta variant and evidence that the vaccines' effectiveness is falling.

The plan, as outlined by the director of the Centers for Disease Control and Prevention and other top authorities, calls for an extra dose eight months after people get their second shot of the Pfizer or Moderna vaccine. The doses could begin the week of Sept. 20.

Health officials said people who received the single-dose Johnson & Johnson vaccine will also probably need extra shots. But they said they are awaiting more data and have yet to work out a plan.

The plan is still awaiting a Food and Drug Administration evaluation of the safety and effectiveness of a third dose, the officials said.

In a statement, health officials said it is "very clear" that the vaccines' protection against infection wanes over time, and now, with the highly contagious delta variant spreading rapidly, "we are starting to see evidence of reduced protection against mild and moderate disease."

"Based on our latest assessment, the current protection against severe disease, hospitalization and death could diminish in the months ahead," they said.

This is a developing story. Check back for updates.

SAN DIEGO, Calif. — Some doctors think there will be a need for a third COVID-19 vaccine "booster" shot.

"At some point, I think it's very likely," said UC San Diego Chief of Infectious Diseases Dr. Davey Smith. "When that point is, I don't know."

A lot is unknown about the need for a booster shot, as the vaccines have only been around for six months. That's barely given researchers time to determine how long they provide complete protection against COVID-19.

Dr. Smith says it's a process that can take years.

"We follow a whole bunch of people who got a vaccine, we measure their immune responses, and then we look and see how often people are getting infected over time," he explains.

"Once we start seeing more infections below a certain level (of antibodies), then we're like, okay, so if somebody has this level of antibody and it dips below that, then perhaps we need a booster at that point," said Dr. Smith.

But measuring antibodies may not be the only indicator of the need for a booster. As the pandemic continues, doctors discover new mutations and variants of COVID-19. There is a strong possibility one of those variants could be resistant to the vaccine, requiring a booster.

"Some of the mutations might be able to evade the immune protection," said Sharp Chula Vista Infectious Disease Specialist Dr. Hai Shao. "As a result, our neutralizing antibodies needs to be tweaked, to be made specifically against the new variants of viruses so that the level of protection can be modified and sustained."

Dr. Shao compares it to the flu, where the yearly vaccine includes several variants. He believes there may be a need for that type of vaccine for COVID-19.

"The likelihood is high," Dr. Shao said. "The question is when do we need the first booster, and how often do we need it after that."

In separate interviews last month, the heads of both Pfizer and Moderna said their vaccines would probably need booster shots. They did not specify when.

Current studies show the vaccines offer protection for at least six months and are effective against all known variants.

Research beyond that is ongoing.

In the meantime, Dr. Shao and Dr. Smith say everyone must get their initial doses of the vaccine to help achieve herd immunity.

"It is important for us to focus our attention and make sure that people who have not gotten the vaccine yet get it in time," said Dr. Shao.

"When you get a vaccine, you're protecting your community," said Dr. Smith. "I really want to get that message out."

This story was originally published by Jared Aarons at KGTV.