LOS ANGELES -- Amid persistent concerns that the protection offered by covid-19 vaccines may be waning, a report released Friday by the Centers for Disease Control and Prevention found that America's workhorse shot is significantly less effective at preventing severe cases of disease over the long term than many experts had realized.
Data collected from 18 states between March and August suggest the Pfizer-BioNTech vaccine reduces the risk of being hospitalized with covid-19 by 91% in the first four months after receiving the second dose. Beyond 120 days, however, that vaccine efficacy drops to 77%.
Meanwhile, Moderna's vaccine was 93% effective at reducing the short-term risk of covid-19 hospitalization and remained 92% effective after 120 days.
Overall, 54% of fully vaccinated Americans have been immunized with the Pfizer shot.
The surprising findings came as a Food and Drug Administration advisory panel recommended against offering booster doses of the Pfizer vaccine to all Americans ages 16 and older. In the panel's decision, 16 of 18 experts told the agency that Pfizer had not mustered enough data to make a third shot the norm.
In lengthy briefings to the panel, representatives from Pfizer pointed to clinical trial results involving 306 mostly healthy participants to argue that a booster "restores" the 95% vaccine effectiveness rate seen earlier in the pandemic.
Company officials also touted evidence from Israel, which rolled out boosters after seeing a rise in hospitalizations among people who were fully vaccinated. Those hospitalizations dropped dramatically after third doses were given, Israeli scientists have said.
But panel members made clear that despite Pfizer's aggressive stance, it had not gathered enough evidence that a third shot was safe for young people and for those at lesser risk of becoming severely ill with covid-19.
"We need age-specific data" on the safety and protective benefits of a booster, said Dr. Ofer Levy, a panel member who directs the Precision Vaccines program at Boston Children's Hospital.
FDA clearance for booster shots for everyone 16 and older would be seen as something "close to a mandate," said Dr. Eric Rubin, a panel member and infectious-disease expert at the Harvard T.H. Chan School of Public Health. Rubin worried that such a move could redefine what it takes to be considered fully vaccinated against covid-19.
"None of us are there yet," he said.
But others apparently are. Dr. Anthony Fauci, President Joe Biden's top adviser on vaccines, has come out strongly in favor of booster shots, saying before Friday's vote that a failure to endorse the shots "would be a mistake."
And in mid-August, Biden said his administration would begin making booster shots available starting Monday to those vaccinated for at least eight months.
Biden cautioned at the time that his plan was contingent on FDA approval. But his announcement stoked concerns of political meddling in a matter that required the unhindered evaluation of scientists.
"This should demonstrate to the public that the members of this committee are independent of the FDA," Dr. Archana Chatterjee, dean of the Chicago Medical School, said after the vote. "In fact, we do bring our voices to the table when we are asked to serve on this committee."
The panel unanimously agreed that a third shot of the Pfizer vaccine should be offered to select groups: individuals 65 and older; people at risk of developing severe disease; and those, including health care workers, whose occupations put them at high risk of infection.
Dr. Peter Marks, who leads the FDA's evaluation of drugs and vaccines, told panel members that the agency could give its blessing to booster shots with an emergency-use authorization -- a regulatory step that falls short of the full approval Pfizer had sought.
The company issued no statement Friday in response to the panel's vote.
U.S. researchers have been warning for months that the immunity afforded by covid-19 vaccines might be waning. The CDC reported that in late July, close to three-quarters of the 469 people swept up in a Massachusetts outbreak were fully vaccinated. And the agency has launched several studies aimed at detecting changes in vaccine effectiveness in health care workers and others who were vaccinated early.
But virtually all of those infections appeared to be mild. And health officials eager to induce vaccine skeptics to step up for their shots -- including Fauci and CDC Director Dr. Rochelle Walensky -- have repeatedly praised the vaccines for keeping most fully vaccinated people out of hospitals.
The new report on waning vaccine efficacy challenges that expectation.
Researchers from around the country found striking differences between two mRNA vaccines previously thought to be interchangeable.
Once the Moderna and Pfizer vaccines were rolled out to the public, their records of preventing covid-19 hospitalizations in the first four months were neck and neck -- 93% and 91% effective, respectively. But the degree of protection diverged after that.
When they focused specifically on the period 120 days beyond the second dose, the study authors found that the Moderna vaccine remained 92% effective at preventing covid-19 hospitalizations. But the equivalent figure for the Pfizer vaccine was 77%.
The results were published in the CDC's Morbidity and Mortality Weekly Report.
Both the Pfizer and Moderna vaccines are based on mRNA technology, which delivers temporary instructions to the body's muscle cells that help it learn to recognize the spike protein, a key part of the coronavirus's structure. But "they're actually not necessarily interchangeable," said Dr. Timothy Brewer, a professor of medicine and epidemiology at UCLA.
Each vaccine is formulated and administered differently, Brewer said, and those differences could affect the strength and duration of the two vaccines' protection.
Moderna's shot contains 100 micrograms of vaccine, more than three times the 30 micrograms in the Pfizer shot. And Pfizer's two doses are given three weeks apart, while Moderna's two-shot regimen is administered with a four-week gap.
Brewer also pointed to evidence that the Moderna vaccine seemed to elicit higher levels of a key antibody than the Pfizer vaccine.
"We know from other studies the neutralizing antibody levels will decay over time, so starting at a higher level will mean that you have farther to go before you decay to a point where efficacy drops off," he said.
Dr. Robert Murphy, who directs Northwestern University's Institute for Global Health, said the Pfizer vaccine's reduced protection against severe disease may bolster the case for boosters for all who got the vaccine, not just the specific groups identified by the FDA advisory panel.
"Based on the data I have seen, persons who received the Pfizer vaccine would benefit from a booster dose at this time," he said. "I don't see why we have to wait until the younger people get sick and become hospitalized."
But Dr. Arnold Monto, who chairs the FDA advisory panel, applauded the agency's willingness to withhold a call for boosters until a stronger case can be made. And he suggested that as more evidence accumulates, boosters for all might still get the nod.
"That's the beauty of the emergency-use authorization," said Monto, an epidemiologist at the University of Michigan. "It can be changed based on changing data."
Many vaccine-resistant Americans are turning to monoclonal antibodies -- a year-old, laboratory-created drug no less experimental than the vaccine -- with a zeal that has, at times, mystified their doctors, chasing down lengthy infusions after rejecting vaccines that cost one-hundredth as much.
Orders have exploded so quickly this summer -- to 168,000 doses per week in late August, up from 27,000 in July -- that the Biden administration warned states last week of a dwindling national supply.
The federal government, which was already covering the cost of the treatment -- currently about $2,100 per dose -- has now taken over its distribution as well. For the coming weeks, the government has told states to expect scaled-back shipments because of the looming shortages.
With seven Southern states accounting for 70% of orders, the new process has unsettled some of their governors, who have made the antibody treatment central to their strategy for enduring a wave of the delta variant.
More supplies are on the way. The federal government bought 1.8 million more doses last week, expected to arrive in the fall and winter. But for now, some hospitals are uncertain of supplies, state health officials said, even as patients keep searching for doses.
"We have providers struggling to get the necessary product," said Kody Kinsley, who leads operations for North Carolina's covid-19 response.
"I think what has happened is a classic logistics issue, where all of a sudden there's much more demand."
Lanson Jones did not think that the coronavirus would be a problem for him. An avid tennis player in Houston who had not caught so much as a cold during the pandemic, he had refused a vaccine because he worried that it would spoil his streak of good health.
But contracting covid-19 shattered his faith in his body's defenses -- so much so that Jones, nose clogged and appetite vanished, began hunting for anything to spare himself a nightmarish illness.
He found the monoclonal antibodies treatment, and in a glass-walled enclosure at Houston Methodist Hospital this month, Jones, 65, became one of more than 1 million patients, including former President Donald Trump, to receive an antibody infusion.
Amid a din of anti-vaccine falsehoods, monoclonal antibodies have become the rare coronavirus medicine to achieve near-universal acceptance. Championed by mainstream doctors and conservative radio hosts alike, the infusions have kept the country's death toll -- 2,000 per day and climbing -- from soaring even higher.
The government-supplied monoclonal antibodies, made by Regeneron and Eli Lilly, have been shown to significantly shorten patients' symptoms and reduce their risk of being hospitalized -- by 70%, in the case of Regeneron's antibody cocktail. The treatment, given in a single sitting, uses lab-made copies of the antibodies that people generate naturally when fighting an infection.
The treatment has won the affection of vaccine refusers who said that the terrors and uncertainties of actually getting covid-19 had made them desperate for an antidote.
"The people you love, you trust, nobody said anything negative about it," Jones said of the antibody treatment. "And I've heard nothing but negative things about the side effects of the vaccine and how quickly it was developed."
After Jones recovered, his doctor was pushing for Jones' vaccination, he said. But the antibodies had worked so well that he was tempted to simply return for another infusion if he caught covid-19 again.
"If I can go get an infusion and feel as good as I do right now, man, I'd rather not take a vaccine that has just been developed," he said. "That makes me nervous, still."
Some Republican governors have set up antibody clinics while opposing vaccine mandates, frustrating even some of the drugs' strongest proponents. Raising vaccination rates, scientists said, would obviate the need for many of the costly antibody treatments in the first place. The infusions take about an hour and a half, including monitoring afterward, and require constant attention from nurses whom hard-hit states often cannot spare.
Doctors have warned that antibody treatments alone cannot keep pace with ballooning outbreaks. Whereas any one vaccination protects untold others from exposure, a single infusion only helps a single patient. Infusions must be given within 10 days of symptoms; they are unhelpful to most hospitalized patients. And receiving the antibodies once does not keep people from becoming seriously ill if they catch the virus again later.
"It's clogging up resources, it's hard to give, and a vaccine is $20 and could prevent almost all of that," said Dr. Christian Ramers, an infectious disease specialist and the chief of population health at Family Health Centers of San Diego, a community-based provider. Pushing antibodies while playing down vaccines, he said, was "like investing in car insurance without investing in brakes."
Information for this article was contributed by Melissa Healy and Amina Khan of the Los Angeles Times (TNS) and by Benjamin Mueller of The New York Times.