: Scientists continue to say there isn’t enough evidence to support giving COVID-19 boosters to all Americans

But the plan has been criticized by medical experts, who say there isn’t enough clinical data demonstrating all Americans vaccinated with the mRNA shots need a booster because they now face a higher risk of severe disease if they do get sick.

“Is it necessary at this point? Does the data justify a mass rollout to 150 million [or] 200 million Americans who are younger and in good health?” asked John Moore, a professor of microbiology and immunology at Weill Cornell Medical College. “What we have got to get away from is this idea that the vaccines are failing, because they’re just not.”

Everyone agrees that giving an extra dose of the vaccines to people who are immunocompromised is a scientifically sound idea; however, the logic for broad administration of COVID-19 booster shots is murky, at best, and scientists and medical experts continue to push back against the lack of evidence.

A group of scientists, including two senior FDA officials who are reportedly retiring later this year, wrote in an opinion piece published Monday in the influential medical journal The Lancet that the “currently available evidence does not show the need for widespread use of booster vaccination” among people who have already been vaccinated.

That assessment came out days before a group of independent advisers is scheduled to meet Friday to discuss whether the FDA should approve BioNTech and Pfizer’s booster shot. The FDA published its own view of the companies’ application for a booster dose on Wednesday, saying that all COVID-19 vaccines in the U.S. continue to provide strong protection against severe disease.

Pfizer’s document, also published Wednesday, argues that everyone who is at least 16 years old who received its vaccine should get a booster. The drug maker’s position is that even though the vaccine continues to protect against hospitalization and severe disease in the U.S., that could change, based on what Pfizer is saying is happening right now in Israel.

Policy makers should consider boosters as a way “to help control heightened transmission of B.1.617.2 (delta) as we enter the upcoming fall/winter viral respiratory season,” Pfizer said.

(Moderna has also filed an application for authorization of a third dose of its COVID-19 vaccine as its vaccine is not yet fully approved by the FDA. Johnson & Johnson
JNJ,
-0.59%
has not filed for authorization of a booster shot at this time.) 

Here’s why the debate about COVID-19 boosters is so complicated

The public-health goal in the pandemic has always been to prevent severe disease, and right now the majority of severe cases, including those that end in hospitalization and death, are occurring in the unvaccinated.

So, even though the number of breakthrough cases among the vaccinated is increasing, it doesn’t change the goal to include preventing infection.

Further, we don’t know if the increase in COVID-19 cases among the vaccinated has more to do with waning immunity or the spread of the more transmissible delta variant. (Pfizer attributes the breakthrough cases to waning immunity.) It’s also unclear what role the relaxation of mitigation measures like wearing masks and social distancing played in the summer surge in cases, which is an issue raised in the Lancet piece.

“Even without any changes in vaccine efficacy, increasing success in delivering vaccines to large populations will inevitably lead to increasing numbers of breakthrough cases, especially if vaccination leads to behavioral changes in vaccinees,” the scientists wrote.

Here’s what we do know COVID-19 boosters will do

The data provided by drug makers indicates that booster shots raise neutralizing antibody titer levels. This is an important metric when assessing protection levels, but it’s not the only one. Scientists also evaluate T-cell response.

Beyond people who are immunocompromised, experts say boosters are more likely to provide additional protection to people who are already at high risk for severe disease, including the elderly and those with serious health conditions. 

SVB Leerink analyst Geoffrey Porges told investors on Thursday that he expects the U.S. will end up rolling out boosters over the next few weeks but only to people who are at least 65 years old at first.

“The recent arguments from outgoing FDA staffers mainly point to issues of international equity and vaccine access, as well as the lack of clinical evidence of need for boosting,” he wrote. “While these are thoughtful arguments in principle, the obligation of the White House, FDA and CDC is to protect American lives, first and foremost.”

The U.S. has been criticized for planning to offer 100 million extra doses to Americans when much of the world has not been vaccinated. But beyond the ethics of a booster program, a limited rollout of extra shots may be frustrating for Americans, particularly the worried-well types, who now assume they will be able to get a booster shot.

“They’ve now created an expectation in the public, at least the public that cares about vaccines. They now expect to get their boosters,” said Weill Cornell’s Moore. “So once you’ve offered the public cake, you can’t take away their cake and say, we’re not going to give you any cake anymore.”

Here’s what you should expect this week

• The FDA’s advisory committee on vaccines is set to meet Friday to vote whether the regulator should authorize BioNTech and Pfizer’s COVID-19 booster shot. This is a public meeting that will be webcast. The FDA is not required to follow the recommendation of the committee but it often does. Moore predicts an “interesting” discussion at the meeting, saying he doesn’t believe that there will be solid agreement among the committee members. “I don’t know which way the majority is going to go,” he said. “But it will not be an unanimous decision.”

• The CDC’s Advisory Committee on Immunization Practices traditionally meets next to make a recommendation about how a vaccine should be administered in the U.S. That vote is then signed off on by CDC director Rochelle Walensky. (This is the same process that was followed for emergency authorization of each COVID-19 vaccine in the U.S.) An ACIP meeting focused on this topic has not yet been scheduled. 

Read more MarketWatch stories about COVID-19 booster shots:

COVID-19 vaccine booster shots are more complicated than they appear. Here’s why.

Doctors question the optics and the scientific rationale behind the plan for COVID-19 booster shots in the U.S.

Pfizer is making the case for COVID-19 booster shots, but Fauci says we don’t need a third dose yet