(CNN)As the Covid-19 vaccine rollout continues in the United States, with people ages 12 and older receiving their shots, vaccine makers are now preparing for a next possible phase: booster doses.

Covid-19 booster shot will likely be needed within a year of vaccination, Fauci says
Covid-19 booster shot will likely be needed within a year of vaccination, Fauci says
Currently three coronavirus vaccines are authorized for emergency use in the United States -- the two-dose Pfizer/BioNTech vaccine for ages 12 and older, the two-dose Moderna vaccine for ages 18 and older and the single-dose Johnson & Johnson vaccines for ages 18 and older.

Researchers and health officials suspect that the immunity against Covid-19 these vaccines elicit in the body might wane over long periods of time -- say, possibly, after a year or more -- and might not protect as well against coronavirus variants that could emerge and evolve.

Therefore, a vaccinated person might need a booster dose of vaccine to stay protected against the original coronavirus strain and newly emerging variants -- somewhat similar to how a tetanus booster is recommended every 10 years or different flu vaccines are recommended each year.

Will booster doses or new vaccines be needed?
"Many people may be familiar with tetanus-toxoid vaccines that are recommended every 10 years -- that's a booster dose. It's reminding our immune system so that if we ever got exposed to that toxin, our immune system would remember it and respond very quickly," Dr. William Moss, professor and executive director of the International Vaccine Access Center at Johns Hopkins Bloomberg School of Public Health, told CNN on Friday.

In the case of Covid-19 vaccines it remains unknown for how long immune protection lasts, but vaccine developers and health officials know it may not be forever -- and that emerging variants could escape immunity.
"There is a little nuance with Covid-19 vaccines," Moss said.

While typical booster doses use same vaccine someone previously received to remind the immune system about immunity to a pathogen, any future boosters for the Covid-19 shot could use different vaccines altogether.

Covid vaccines can take on new coronavirus variants, studies show
Covid vaccines can take on new coronavirus variants, studies show
Currently, "the need for and timing for COVID-19 booster doses have not been established. No additional doses are recommended at this time," the US Centers for Disease Control and Prevention notes on its website.

But Americans should prepare to have a Covid-19 vaccine booster shot within a year, US Surgeon General Dr. Vivek Murthy told CNN's Wolf Blitzer on Thursday.

"We have to see how long the protection lasts. We know it lasts at least six months, but we'll have to see," Murthy said. "It's very possible, though, and people should be prepared for the fact that we may need a booster within a year."

How often will you need a Covid-19 booster?
Despite such predictions, Dr. Anthony Fauci, director of the National Institute of Allergy and Infectious Diseases, told CNN the bottom line is "we don't know."

"We're preparing for the eventuality that we might need boosters, but I think we've got to be careful not to let the people know that inevitably, x number of months from now, everyone's going to need a booster. That's just not the case," Fauci, chief medical adviser to President Joe Biden, said at a Washington Post Live event. "We may not need it for quite a while."

Scientists at a number of companies that make Covid-19 vaccines have also predicted the need for boosters within a year -- but the scientific community is not in widespread agreement on this.

"We're making extrapolations" from incomplete data, Fauci told The Washington Post on Thursday.

So far, studies have shown that mRNA vaccines -- those made by Pfizer and Moderna -- maintain more than 90% efficacy six months after getting vaccinated. And scientists say it's likely much longer.

Other studies have looked at antibodies in the lab. While a decline is expected over time, Fauci told the Post "the steepness of that slope is unclear right now."

Experts say it is also unclear how these antibody levels correlate with real-world immunity, and to what extent other parts of the immune system -- such as T cells -- could factor into protection.

What happens if you skip the booster?
Whether booster coronavirus vaccine doses are modified or not, missing a booster dose -- if one is recommended in the future -- could leave someone less protected against Covid-19.
"A person who skipped a booster is placing themselves at higher risk of getting infected, and getting disease from the SARS-Coronavirus-2, but I would also expect that they're going to have some partial immunity and so they may be protected against more severe disease," Moss said. SARS-CoV-2 is the virus that causes Covid-19.
"It's just a function of how much their immunity has waned or how different a variant is," he said. "They're just at higher risk of infection and disease than someone who got the booster, but they have more immunity than someone who was never vaccinated."
Scientists are also currently investigating whether it makes a difference if someone gets the same type of vaccine as a booster as the original dose administered.
"This question of mixing and matching certainly is relevant to booster doses," Moss said. "It's also relevant to any two-dose vaccine schedule, and it's also an area of active research."
Mixing Covid-19 vaccines tied to more side effects, early UK data suggests
Mixing Covid-19 vaccines tied to more side effects, early UK data suggests
Researchers in the United Kingdom reported last week that people who got mixed doses of coronavirus vaccines -- receiving a different vaccine type as a second dose than the first dose -- appear to be more likely to experience mild side effects such as fever, chills, fatigue or headache.
But the side effects following mix-and-match vaccinations were short-lived and there were no other safety concerns, the researchers reported in the Lancet medical journal.
As for booster doses in the future, "I can very much envision a situation in which people might get a very different type of vaccine for that booster dose than they had originally," Moss said. "The big question I have, I guess, is how much underlying scientific evidence are we going to have to support that to actually make it a recommendation? That I don't know yet, but it's certainly likely to happen by default, just because perhaps the original vaccine is not available."
Currently, the CDC says, "Covid-19 vaccines are not interchangeable" and there has been no decision either in the US or globally on the need for booster doses yet, let alone which vaccine might be appropriate for any booster.
Who is making booster shots?
All three companies that currently have authorized coronavirus vaccines in the United States -- Pfizer, Moderna and Johnson & Johnson -- are investigating the potential use of boosters.
"We are right now in the middle of these trials and the data are coming as we speak," Pfizer CEO Albert Bourla told Axios during a virtual event on Wednesday.
"The data that I see coming, they are supporting the notion that likely there will be a need for a booster somewhere between eight and 12 months," Bourla said. " But that remains to be seen and I believe in one, two months we will have enough data to speak about it with much higher scientific certainty."
The first dose of Pfizer's coronavirus vaccine in the United States was administered on December 14, 2020 -- five months ago. As time goes on, if people received their second dose of vaccine eight months ago, "they may need a third one," Bourla said. "This could be coming sooner than later, I believe from September, October. But this is something, again, that the data need to confirm."
Moderna, Pfizer test vaccine strategies against new variants
Moderna, Pfizer test vaccine strategies against new variants
Moderna is currently conducting booster shot trials too.
The fight against the coronavirus pandemic is expected to continue through next year due to the emergence of variants, Dr. Stephen Hoge, president of Moderna, said during an earnings call earlier this month.
"We think this is just the beginning," Hoge said. "Therefore, we're committed as a company to make as many updates to the vaccine, to add as many variants as we think are necessary, to ensure that when people receive a booster, it provides the broadest immune protection against the widest range of variants."
Johnson & Johnson is also looking into the potential for boosters.
"We have ongoing and planned trials that will aid our assessment of the need for, and timing of, booster doses of our vaccine," according to an emailed statement Johnson & Johnson sent to CNN on Thursday.
Johnson & Johnson's coronavirus vaccine, along with Pfizer's, Moderna's, and four others, are being tested as seasonal boosters in a study called Cov-Boost being conducted by the UK's National Institute for Health Research and the University of Southhampton.
Novavax to seek US authorization of its Covid-19 vaccine in third quarter, CEO says
Novavax to seek US authorization of its Covid-19 vaccine in third quarter, CEO says
The biotechnology company Novavax has developed a coronavirus vaccine that its chief executive officer Stanley Erck believes could be used as a booster shot for people who have already been vaccinated. The company plans to apply for emergency use authorization of its vaccine in the United States in the third quarter of 2021.
"In the US, I think it will be the booster for everyone, particularly if we get it out late in the third quarter," Erck told CNN last week. "It's going to be time to start boosting -- whether it's six months or at a year point."
Who has to OK the Covid-19 booster shots?
The decision to use Covid-19 boosters is expected to involve two agencies -- the US Food and Drug Administration and the CDC -- and the regulatory process to get the shots into arms could vary depending on whether the booster is the same vaccine that was originally used or is a modified version.
"So, if it's the same vaccine, my understanding is that what would have to happen is that the CDC would have to recommend an additional dose with details around when that should occur," Moss said.
If it's a modified vaccine, "this is where things get interesting and I don't think we quite know," he said, but added that the regulatory process could be similar to what happens with flu vaccines each year.
"Technically, whenever a vaccine like that is modified, it's often considered a new vaccine and has to go through the whole process again. But there is a precedent, obviously, with influenza virus vaccines, not to do that," Moss said. "So, the influenza vaccine each year doesn't have to go through a large Phase 3 trial."
That's because the vaccine technology stays the same, and the only change is the flu virus itself that the vaccine targets to elicit immunity to a specific flu virus strain that's circulating.
Moss said that's what he expects could happen with modified coronavirus vaccines.
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"At this time, available information suggests that the FDA-authorized vaccines remain effective in protecting the American public against currently circulating strains of SARS-CoV-2. However, if there is an emergence of SARS-CoV-2 variant(s) in the U.S. that are moderately or fully resistant to the antibody response elicited by the current generation of COVID-19 vaccines, it may be necessary to tailor the vaccines to the variant(s)," an FDA spokesperson told CNN on Thursday.
The FDA updated its guidance for vaccine developers in February, noting that manufacturers should "generate the data to support authorization" of a modified vaccine.
"Further discussions will be necessary to decide whether in the future, modified COVID-19 vaccines may be authorized without the need for clinical studies," according to the guidance. But overall, vaccine developers are "encouraged" to perform exploratory studies on modified vaccines to boost immune responses.

CNN's Virginia Langmaid, Michael Nedelman and Jen Christensen contributed to this report.

(CNN) 12세 이상 사람들이 주사를 맞으면서 미국에서 코로나19 백신 출시가 계속됨에 따라 백신 제조사들은 이제 다음 단계인 부스터 선량을 준비하고 있다.

Fauci는 백신 접종 후 1년 이내에 코로나19 촉진제 주사를 맞아야 할 것이라고 말했다.
Fauci는 백신 접종 후 1년 이내에 코로나19 촉진제 주사를 맞아야 할 것이라고 말했다.
현재 미국에서는 3개의 코로나 바이러스 백신이 비상용으로 허가되어 있다. - 2회 복용량의 화이자/바이오.NT테크 백신은 12세 이상, 2회 복용 모데나 백신은 18세 이상, 1회 복용 존슨&존슨 백신은 18세 이상이다.

연구원들과 보건 관계자들은 이러한 백신이 체내에서 유도하는 코로나19에 대한 면역력이, 예를 들어, 1년 이상 지나면, 장기간에 걸쳐 저하될 수 있으며, 출현하거나 진화할 수 있는 코로나바이러스 변종으로부터 보호하지 못할 수도 있다고 의심하고 있다.

따라서 백신을 접종한 사람은 원래 코로나 바이러스 변종과 새롭게 출현하는 변형으로부터 보호받기 위해 부스터 용량 백신이 필요할 수 있다. 이는 10년마다 파상풍 부스터가 권장되는 방식과 다소 유사하거나 매년 다른 독감 백신이 권장된다.

복용량을 증가시키는 것이 필요할까 아니면 새로운 백신이 필요할까?
"많은 사람들은 10년마다 권장되는 파상풍 독소성 백신을 알고 있을 것입니다. 그것은 촉진제입니다. 이것은 우리의 면역 체계를 상기시켜주어 만약 우리가 그 독소에 노출된다면, 우리의 면역체계가 그것을 기억하고 매우 빠르게 반응할 것입니다,"라고 존스 홉킨스 블룸버그 공중보건대학 국제백신접속센터의 윌리엄 모스 박사가 금요일 CNN에 말했습니다.

코로나19 백신의 경우 면역 보호가 얼마나 오래 지속되는지는 알 수 없지만 백신 개발자와 보건 관계자들은 이것이 영원하지 않을 수도 있고 새로운 변종이 면역에서 벗어날 수 있다는 것을 알고 있다.
"코로나19 백신에는 약간의 뉘앙스가 있습니다,"라고 모스는 말했다.

일반적인 부스터 선량은 이전에 받은 것과 동일한 백신을 사용하여 면역체계에 병원체에 대한 면역력에 대해 상기시키지만, Covid-19 주사에 대한 모든 향후 부스터는 모두 다른 백신을 사용할 수 있다.

코로나 바이러스 변종에서 코로나 백신이 나올 수 있다는 연구 결과가 나왔다.
코로나 바이러스 변종에서 코로나 백신이 나올 수 있다는 연구 결과가 나왔다.
현재 "COVID-19 부스터 선량에 대한 필요성과 타이밍은 확립되지 않았다. 현재로서는 추가 선량이 권장되지 않습니다."라고 미국 질병통제예방센터는 웹사이트에 언급하고 있습니다.

하지만 미국인들은 1년 안에 코로나19 백신 부스터 주사를 맞을 준비를 해야 한다고 비벡 머시 미국 외과의사가 목요일 CNN의 울프 블리처에게 말했다.

"우리는 보호가 얼마나 오래 지속되는지 봐야 합니다. 우리는 그것이 최소한 6개월 동안 지속된다는 것을 알지만, 우리는 봐야 할 것입니다,"라고 머시는 말했다. "하지만 이것은 매우 가능성이 있고, 사람들은 우리가 1년 안에 촉진제가 필요할지도 모른다는 사실에 대비해야 합니다."

코로나19 촉진제가 얼마나 자주 필요할까요?
이러한 예측에도 불구하고, 국립 알레르기 및 전염병 연구소의 책임자인 앤서니 파우치 박사는 결론은 "우리는 모른다"라고 CNN에 말했다.

"우리는 부스터가 필요할 수도 있는 만일의 사태에 대비하고 있습니다. 하지만 저는 사람들에게 앞으로 몇 달 후 모든 사람들이 부스터가 필요하다는 것을 알리지 않도록 조심해야 한다고 생각합니다. 조 바이든 대통령의 수석 의학 고문인 파우치는 워싱턴 포스트 라이브 행사에서 이렇게 말했다. "우리는 한동안 그것이 필요하지 않을지도 모릅니다."

코로나19 백신을 만드는 많은 회사의 과학자들 또한 1년 안에 부스팅의 필요성을 예측했지만 과학계는 이에 대해 널리 동의하지 않고 있다.

파우치는 목요일 워싱턴포스트와의 인터뷰에서 불완전한 자료에서 "추측을 하고 있다"고 말했다.

지금까지의 연구에 따르면, 화이자와 모데나가 만든 mRNA 백신은 백신 접종 후 6개월이 지난 후에도 90% 이상의 효능을 유지하고 있다. 그리고 과학자들은 그것이 훨씬 더 길 것이라고 말한다.

다른 연구들은 실험실의 항체를 조사했습니다. 시간이 지남에 따라 감소가 예상되지만, 파우치는 포스트지에 "지금 그 경사의 경사가 불분명하다"고 말했다.

전문가들은 또한 이러한 항체 수치가 실제 면역력과 어떻게 상관관계가 있는지, 그리고 T세포와 같은 면역체계의 다른 부분들이 어느 정도까지 보호될 수 있는지 불분명하다고 말한다.

부스터는 건너뛰면 어떻게 됩니까?
부스터 코로나바이러스 백신 선량이 수정되었는지 여부에 관계없이 부스터 선량이 누락되면 코로나바이러스 백신 선량이 코로나19로부터 덜 보호될 수 있다.
모스는 "보충제를 건너뛴 사람은 사스-코로나바이러스-2에 감염될 위험이 더 높다"며 "그러나 사스-코로나바이러스-2에 감염될 위험이 더 높다"고 말했다. 사스-CoV-2는 코로나19를 일으키는 바이러스이다.