The U.S. hasn't yet managed to get 70% of Americans vaccinated with at least one shot against COVID-19 — a Biden administration goal — but the federal government and drug makers are already planning ahead for a possible booster shot later this year.
Other countries, like Israel, started this week to administer a third vaccine dose to bolster the immunity of those vulnerable to SARS-CoV-2, the virus that causes COVID-19.
Pfizer and Moderna are looking at new potential vaccine formulas tweaked to target mutationsfirst spotted in India. However, so far, the data show that full vaccination is sufficient to protect against Delta and other variants. Early results also suggest a third shot of the vaccine, virtually identical to the first two doses, might provide a boost in protection.
Some other countries are mulling boosters by proven drugmakers, over concerns that people who were vaccinated early on with less effective doses — like Thai medical workers who were given Chinese-made Sinovac-CoronaVac shots — may need extra protection.
Here's what to know about COVID-19 booster shots:
Do I need a booster shot right now?
But Biden administration officials and vaccine makers say booster shots will "probably" be needed eventually for Americans with declining immunity.
For now, researchers have detected only modest reductions in antibodies in people's blood months after they were first vaccinated.
And health officials have noted that in the United Kingdom and Israel, the Pfizer and Moderna vaccines remain highly effective at preventing severe illness and death, even amid surging Delta variant cases there, though a greater share of vaccinated people are contracting the disease and have shown mild symptoms. Johnson & Johnson has also released data from a small study suggesting its vaccine also had "strong, persistent activity" in laboratory tests against the Delta variant.
The Food and Drug Administration, which regulates vaccines, and the Centers for Disease Control and Prevention, which decides on how authorized shots will be deployed in the U.S., are still gathering data on boosters.
"We are prepared for booster doses if and when the science demonstrates that they are needed," the CDC and FDA said in a statement.
When will we know if we need a booster shot?
As early as this fall, U.S. regulators could decide whether some people should get booster shots.
Vaccine manufacturers and the federal government have launched trials examining the value of an additional vaccine dose. Pfizer representatives met this week with Biden administration officials to discuss their most recent data.
Pfizer announced it saw "encouraging data" in its booster shot trial, suggesting the extra shot was effective at raising immunity without serious side effects. A spokesperson for the company told CBS News the company plans to publish more detailed results from its trial by August and then seek emergency use authorization from the FDA for a third dose.
"You're talking about a process that's probably at least a couple of months long," Dr. Scott Gottlieb, a Pfizer board member and former FDA commissioner, told "Face the Nation".
Early results from Moderna's booster shot trials are expected by September, along with research into "breakthrough" infections among fully vaccinated people.
By then, FDA officials say they also hope to have more real-world data on the people who received the vaccine in the earliest phase of the rollout — health care workers and older Americans in long-term care facilities.
"We need to look at how their immunity is waning and are they starting to get infected at some point, or is their immunity dropping down to a level where they might not be able to fight against the virus," acting FDA Commissioner Dr. Janet Woodcock said in May.
Who might need a booster shot?
A small share of fully vaccinated people, ranging from those vaccinated earliest to older Americans and the immunocompromised, could be among those who need boosters first.
- Immunocompromised: Those with weakened immune systems, like people undergoing treatment for cancer or those who received an organ transplant, likely received less protection from the vaccination. But there may be good news for these patients — a recent study of organ transplant recipients who appeared not to respond to their first two doses of the Pfizer vaccine in France found close to half saw improved antibody responses after a third dose. U.S. recommendations for booster shots for immunocompromised Americans could come soon, at a July 22 meeting of the CDC's independent panel of vaccine advisers.
- Older Americans: In the U.K., health authorities are already planning to offer booster shots in September to all adults 70 and older, as well as other high-risk groups like frontline health care workers.
- Maybe not children: Children may be able to go longer without booster shots. Vaccines are not yet authorized for children under 12, but could be later this year. "Because children make such good immune responses they may not need to be revaccinated if boosters are necessary. They may not need to be revaccinated quite as soon as adults," Dr. Peter Marks, a top FDA vaccine official, said in May.
Who will make the booster shots?
Moderna has announced plans to make booster doses for the U.S.
The company said last month that the Biden administration had purchased 200 million more doses through early 2022, which could serve either to vaccinate children or as a booster shot "if that becomes necessary."
Pfizer has not announced specific plans to manufacture booster shots, but the U.S. has millions of doses available for future needs.
Will I have to get a booster shot from the same manufacturer as my first dose?
Scientists are researching whether it would be safe and effective to "mix and match" booster shots from one manufacturer with earlier doses from another.
The NIH expects the initial results of a study mixing Moderna with Pfizer and with Johnson & Johnson as a booster by later this summer.
Early research by countries using AstraZeneca's vaccine suggests mixing its first doses with second doses of Pfizer's shots may have boosted immunity, though health officials warn mixing booster shots could risk worse side effects.
"It's a little bit of a dangerous trend here where people are in a data-free, evidence-free zone as far as mix-and-match. There's limited data on mix-and-match," Dr. Soumya Swaminathan, the World Health Organization's chief scientist, told reporters on Monday.
Will I have to pay for a booster shot?
No. The Biden administration says the next round of booster shots will be free, same as the current batch of doses.