Scientists have long said that giving people a single course of a Covid-19 vaccine might not be sufficient in the long term, and that booster shots and even annual vaccinations might prove necessary.
In recent days, that proposition has begun to sound less hypothetical.
Vaccine makers are getting a jump-start on possible new rounds of shots, although they sound more certain of the need for boosters than independent scientists have.
Pfizer’s chief executive Albert Bourla said on Thursday that a third dose of the company’s Covid-19 vaccine was “likely” to be needed within a year of the initial two-dose inoculation — followed by annual vaccinations.
Albert Bourla, the Pfizer chief, said in a conversation hosted by CVS Health, that people may need to get Covid vaccine shots annually, like flu shots. Some vaccines are only given once, while others need annual boosters, he said. (An earlier version of this post included a quoted comment in which he misstated the number of vaccine doses required for polio immunity — more than one dose is needed.)
Dr. David Kessler, who runs the Biden administration’s vaccine effort, told a House subcommittee on Thursday that the government was also looking ahead. One factor at play is the spread of coronavirus variants and whether further vaccination could better target mutant strains.
Mr. Bourla said that “a likely scenario” is “a third dose somewhere between six and 12 months, and from there it would be an annual re-vaccination.” Moderna said this week that it was at work on a booster for its vaccine, and Johnson & Johnson has said that its single-shot vaccine will probably need to be given annually.
Dr. Kessler emphasized the “strong efficacy” of the current vaccines, including against the variants, but said that the government was “taking steps to develop next generation of vaccines that are directed against these variants if in fact they can be more effective.”
He was one of a handful of top federal health officials at the House hearing who implored Americans to get vaccinated and sought to reassure the nation that all three federally authorized vaccines are safe. They said little about restarting Johnson & Johnson shots, which came to a halt after the Food and Drug Administration called for paused to examine a rare blood-clotting disorder. It is unclear whether the vaccine was responsible for the clots.
Late Thursday, the Centers for Disease Control and Prevention said it had scheduled a new emergency hearing for April 23. The agency’s independent vaccine advisory panel, known as the Advisory Committee on Immunization Practices, or ACIP, has been scheduled to meet then for a second time since shots were halted, to discuss safety data related to a small number of blood-clotting cases in Johnson & Johnson vaccine recipients.
“We recognize the critical importance of moving quickly. That’s why we will have two unscheduled ACIP meetings in a 10-day period,” Dr. Rochelle P. Walensky, the C.D.C. director, said at a White House news conference Friday.
- On April 13, 2021, U.S. health agencies called for an immediate pause in the use of Johnson & Johnson’s single-dose Covid-19 vaccine after six recipients in the United States developed a rare disorder involving blood clots within one to three weeks of vaccination.
- All 50 states, Washington, D.C. and Puerto Rico temporarily halted or recommended providers pause the use of the vaccine. The U.S. military, federally run vaccination sites and a host of private companies, including CVS, Walgreens, Rite Aid, Walmart and Publix, also paused the injections.
- Fewer than one in a million Johnson & Johnson vaccinations are now under investigation. If there is indeed a risk of blood clots from the vaccine — which has yet to be determined — that risk is extremely low. The risk of getting Covid-19 in the United States is far higher.
- The pause could complicate the nation’s vaccination efforts at a time when many states are confronting a surge in new cases and seeking to address vaccine hesitancy.
- Johnson & Johnson has also decided to delay the rollout of its vaccine in Europe amid concerns over rare blood clots, dealing another blow to Europe’s inoculation push. South Africa, devastated by a more contagious virus variant that emerged there, suspended use of the vaccine as well. Australia announced it would not purchase any doses.
She said that the C.D.C. had contacted over 10,000 providers “to ensure that they know what kinds of cases to look for.”
As of Thursday, more than 125 million people in the country had received at least one dose of a Covid-19 vaccine, including about 78 million who have been fully vaccinated by Johnson & Johnson’s single-dose vaccine or the two-dose series made by Pfizer-BioNTech and Moderna.
In February, Pfizer and its partner, BioNTech, said that they planned to test a third shot and to update their original vaccine. The F.D.A. has said that vaccine developers will not need to conduct lengthy trials for vaccines that have been adapted to protect against variants.
On Tuesday, Moderna said that its vaccine continued to provide strong protection in the United States against Covid-19 six months after it is given, and the company’s chief executive, Stéphane Bancel, told CNBC that he hoped to have booster shots ready by the fall.