- The United States cleared the first rewording of Covid’s recall shots this week.
- The new doses target the dominant omcron subvariants and the original Covid strain that emerged in China in 2019.
- Top health officials believe the shots will provide more lasting protection ahead of the fall, but they acknowledge that it’s not yet clear how effective they will be.
The United States authorized the first major makeover of Covid-19 vaccines this week in an effort to stem the expected wave of infections and hospitalizations this fall.
But it’s unclear how much protection the new lure shots will provide. The Food and Drug Administration and Centers for Disease Control and Prevention have cleared the shots without any data from clinical trials that are testing reformulated doses in humans.
The new boosters, licensed for people 12 years of age and older, target the highly contagious and immune evasive subvariant omicron BA.5 that caused a wave of breakthrough infections over the summer. The shots also target the original strain of the virus that first emerged in Wuhan, China, in 2019.
The nation’s top health officials took urgent action this summer to ensure the new boosters would be launched in time for the fall. They are concerned that the declining effectiveness of older vaccines is creating an opening for omicron to cause another wave of hospitalizations this winter as people spend more time indoors where the virus spreads more easily.
Deaths and hospitalizations have increased since April among the elderly, the most vaccinated age group in America, as omcron has continued to mutate into increasingly transmissible subvariants that elude the protection of the original vaccines, according to Heather Scobie, a CDC epidemiologist. .
Dr Peter Marks, who heads the FDA’s office that examines vaccines, said the new boosters aim to restore the high levels of protection demonstrated by vaccines in early 2021. But Marks acknowledged that federal government experts they just don’t know yet if the boosters will meet the high bar set by those doses.
“We still don’t know for sure if we’ll reach the same level, but that’s the goal here. And that’s what we believe the evidence we’ve seen helps to indicate,” Marks told reporters at a news conference following the clearance of the FDA Wednesday.
The FDA will conduct surveillance to see if the boosters meet that goal, Marks said. When Pfizer and Moderna’s shots were cleared in December 2020, they provided over 90% protection in preventing Covid.
Marks told reporters that it will likely take at least another couple of months for human data on the BA.5 boosters to be available to the public. But she said the FDA has used pretty much the same process to authorize the new boosters it has relied on for years to change viral strains in flu vaccines.
“We are pretty confident that what we have is very similar to the situation we have done in the past with influenza changes where we don’t do clinical trials for them in the US,” Marks said. “We know from the way the vaccine works and from the data we have, that we can predict how well the vaccine will work.”
The new boosters could prevent 2.4 million infections, 137,000 hospitalizations and 9,700 deaths if a new variant does not emerge, according to a projection by a team of scientists that predicts the trajectory of the pandemic, called the Covid-19 scenario modeling hub.
But that projection is based on optimistic assumptions about booster coverage and effectiveness, according to the scientists. The model assumes that hits will prove 80% effective in preventing disease, and the public will embrace the new boosters broadly. There is no efficacy data on the new hits and it is unclear how strong public demand will be for them.
The CDC estimates that an autumn booster vaccination campaign could save the United States between $ 63 and $ 109 billion in medical costs by preventing hospitalizations and ICU admissions.
Pfizer and Moderna were originally developing new boosters to target omicron’s first version, BA.1, which caused the massive wave of infections and hospitalizations last winter. But keeping up with the rapid evolution of the virus proved challenging.
By the time the nation’s top health leaders got serious in April to make new boosters, the more transmissible sub-variants had already eliminated omicron BA.1 from prevalence. In June, the FDA asked vaccine manufacturers to shift gears and target omicron BA.5 after it rose to dominance.
This decision didn’t leave enough time for Pfizer and Moderna to complete human clinical trials of the new boosters ahead of the fall vaccine launch.
As a result, the FDA and CDC rely on human data from clinical trials of BA.1 shots to understand how BA.5 boosters might work. They also relied on data from studies where BA.5 boosters were tested on mice.
The CDC’s independent advisory board backed the shoot with an overwhelming vote on Thursday.
But several panel members also had reservations about the lack of human data.
“I really struggle with a vaccine that has no clinical data reported for humans, for those who would actually receive the vaccine,” said Dr. Oliver Brooks, board member and medical director of Watts HealthCare Corp. in Los Angeles.
Dr Pablo Sanchez, the only member of the CDC committee who voted against the shooting, called the decision to recommend the new boosters without human data premature.
“There is already a lot of hesitation about the vaccine – we need the human data,” said Sanchez, a professor of pediatrics at Ohio State University.
Dr Doran Fink, deputy head of the FDA’s vaccine review division, told hesitant committee members that the new booster shots use the exact same manufacturing process as the old vaccines and contain the same total amount of mRNA, the code which instructs human cells to produce the proteins that cause an immune response to defend against Covid.
Fink said that the BA.1 and BA.5 hits are similar enough to use the BA.1 human trials data to get a good idea of how the new BA.5 boosters will perform.
Pfizer and Moderna presented data at the CDC meeting that showed BA.1 shots triggered a stronger immune response in humans than older vaccines. Mouse studies from both companies on BA.5 shots also showed a stronger immune response.
Last week, CDC Director Dr Rochelle Walensky said waiting longer for human data from BA.5 hits could mean boosters will become obsolete if a new variant emerges.
“There’s always a question of being too slow or too fast,” Walensky told Conversations on Health Care in a radio interview. “One of the challenges is if we wait for that data to emerge in human data … we will use what I consider to be a potentially obsolete vaccine.”
Moderna completed enrollment in its clinical trials last week and expects results by the end of the year. Pfizer’s clinical trials are ongoing, although the company hasn’t provided a time frame as to when it will have the data.
Brooks wondered why the FDA decided to adopt a BA.5 vaccine when clinical data is available for the BA.1 shots that vaccine manufacturers were originally developing. Canada and the UK have authorized new decoy shots targeting omicron BA.1
Fink said the United States selected BA.5 based on the advice of the FDA’s independent committee, data from South Africa indicating that natural infection from the sub-variant provides broader protection than BA.1 infection and the fact that BA.5 is dominant.
Although committee members hesitated to proceed without human data, they agreed that the new boosters should have a similar safety profile to the old vaccines because they use the same platform. Covid vaccines have been given to millions of people in the United States with mostly mild side effects.
The most common side effects of human trials of BA.1 shots were pain, redness, swelling at the injection site, fatigue, headache, muscle pain, joint pain, chills, nausea, vomiting, and fever, according to the FDA.
Dr. Sara Oliver, a CDC official, told the committee that the risk of myocarditis, inflammation of the heart muscle, after a BA.5 recall is unknown. But health officials predict it will be similar to the risk seen with older vaccines.
Pfizer and Moderna vaccines have been associated with a high risk of myocarditis in young men and adolescent boys mainly after the second dose. But the risk of myocarditis is greater from Covid infection than vaccination, according to the CDC.
Dr Grace Lee, chair of the CDC committee, tried to reassure the public that there is a robust surveillance system to monitor safety and that the panel will meet again if new concerns emerge.
“I just want to make sure audience members are aware that we are continuing to monitor closely,” Lee said. “We have systems and teams that keep monitoring and meeting.”