Tuesday, October 19, 2021

Big gap between Pfizer, Moderna jabs for preventing hospitalisations

  • Sep 18, 2021
  • Author: QT-Online
  • Number of views: 12800
  • Health/Medicine
Los Angeles
Amid persistent concerns that the protection offered by COVID-19 vaccines may be waning, a report released on Friday by the Centers for Disease Control and Prevention finds that America's workhorse shot is significantly less effective at preventing severe cases of disease over the long term than many experts had realised.
Data collected from 18 states between March and August suggest the Pfizer-BioNTech vaccine reduces the risk of being hospitalised with COVID-19 by 91 percent in the first four months after receiving the second dose. Beyond 120 days, however, that vaccine efficacy drops to 77  percent.
Meanwhile, Moderna's vaccine was 93  percent effective at reducing the short-term risk of COVID-19 hospitalisation and remained 92  percent effective after 120 days.
Overall, 54  percent of fully vaccinated Americans have been immunised 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 a striking rebuke, 16 of 18 experts told the agency it 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  percent 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 hospitalisations 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 further booster, said Dr Ofer Levy, a panel member who directs the Precision Vaccines programme 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 favour of booster shots, saying before Friday's vote that a failure to endorse the shots "would be a mistake." And in mid-August, Biden himself said his administration would begin making booster shots available the week of September 20 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 vaccine now sold under the brand name Comirnaty 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 on Friday in response to the panel's vote.
Researchers in the United States 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 healthcare 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 shot - including Fauci and Dr. Rochelle Walensky, director of the Centers for Disease Control and Prevention - 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 long thought to be interchangeable.
When the Moderna vaccine received emergency use authorisation in December, the company reported that 30 people in its clinical trial developed severe cases of COVID-19, including nine who required hospitalization. All 30 patients were in the placebo group, resulting in a vaccine efficacy against severe disease of 100  percent.
Ten people in Pfizer's initial clinical trial developed severe cases of COVID-19. Nine of them was in the placebo group, including seven who were hospitalized, resulting in a vaccine efficacy against severe disease of 88.9  percent.
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  percent and 91  percent 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  percent effective at preventing COVID-19 hospitalizations. But the equivalent figure for the Pfizer vaccine was 77  percent.
The results were published in the CDC's Morbidity and Mortality Weekly Report.