A medical worker prepares a booster dose of Pfizer’s coronavirus disease (COVID-19) vaccine at a vaccination center in Brussels, Belgium, January 5, 2022.
Yves Herman | Reuters
The Food and Drug Administration on Wednesday approved Covid booster shots targeting the omicron BA.5 subvariant as the US braces for a further spike in infections this fall and winter.
It is the first time since the original vaccines were introduced in December 2020 that the FDA has approved an updated vaccine formula. Pharmacies are expected to begin dispensing the new boosters after Labor Day weekend.
So far, the US has secured 171 million doses of the updated Pfizer and Moderna vaccines, according to the Department of Health.
Pfizer’s new booster vaccine is approved for people 12 and older, while Moderna’s new vaccines are approved for adults 18 and older. The eligible age groups can receive the boosters two months after the completion of their primary series or their last booster with the old vaccinations.
The US will stop using the original vaccines as booster doses for people 12 and older after the updated vaccines are approved by the FDA, according to the FDA.
The Centers for Disease Control and Prevention must approve the boosters before pharmacies can distribute them to patients. The CDC’s independent advisory committee is scheduled to meet Thursday and Friday to review the data and issue its recommendations for health care providers.
Public health officials believe the redesigned boosters will offer longer-lasting protection against the virus and reduce hospitalizations this fall and winter. The new boosters target both the original strain, which emerged in China more than two years ago and which scientists call “wild type,” and omicron BA.4 and BA.5, which are now the dominant variants in the US
Vaccines that target two different strains are called bivalent vaccines.
Vaccine manufacturers developed the original vaccines against the Covid strain that first emerged in Wuhan, China in 2019. But the virus has changed dramatically since then. Omicron and its subvariants have strayed so far from the original Covid strain that the virus can slip past the protective antibodies induced by the vaccines.
As a result, the effectiveness of vaccinations in preventing infections and minor illnesses has decreased significantly as the virus has evolved. Although vaccines still generally prevent serious illnesses, the protection they offer from hospitalization has also diminished over time.
“Efficacy against hospitalization and serious illness is declining. The problem has been persuading the American people to strengthen themselves regularly,” said Dr. Peter Hotez, an infectious disease expert at Baylor College of Medicine in Texas. Hotez led a team that developed a protein-based Covid vaccine that is approved in India.
Original vaccines are losing effectiveness
About 76% of people ages 12 and older in the US have had their first two doses of the vaccine, according to CDC data. About 50% of these people have received their first booster shot.
In adults 18 years and older, three doses of original Pfizer or Moderna vaccines were 55% effective four months after the third dose in preventing hospitalization for the omicron BA.2 subvariant, according to CDC data.
According to CDC data from August 2021 to May 2022, three injections prevented infection by omicron by 19% five months after the third injection. The fast-spreading BA.4 and BA.5 subvariants have since phased out omicron BA.2.
dr Peter Marks, head of the FDA’s office responsible for reviewing vaccines, said the hope is that the updated boosters will restore the high level of protection against disease that vaccines showed when they were first approved in December 2020.
“We don’t yet know exactly if we’ll reach the same level, but that’s the goal here. And we think the evidence we’ve seen suggests that,” Marks told reporters during a post-approval news conference Wednesday.
The Biden administration moved quickly over the summer to prepare updated shots for the fall. Public health officials are concerned the US is on the verge of another wave of infections as more transmissible omicron variants spread, immunity to the original vaccines wanes and people go indoors to escape the colder weather.
Pfizer and Moderna originally developed boosters against omicron BA.1, the variant that caused the massive wave of infections last winter. But the FDA in late June urged vaccine makers to shift gears and target BA.4 and BA.5 instead, as those variants were quickly gaining ground. The sudden change in plans left little time for human clinical trials ahead of a fall launch.
As a result, the approval is based on human clinical trials of the BA.1 shots, which the FDA says elicited a better immune response than the original doses. However, it is unclear how the BA.5 boosters will behave in humans since the data are based on BA.1.
Marks said it will likely be at least two more months before clinical data on the BA.5 shots is released to the public.
According to the FDA, the most common side effects from the human trials of BA.1 syringes were pain, redness, swelling at the injection site, fatigue, headache, muscle pain, joint pain, chills, nausea, vomiting, and fever. The Covid vaccines have a well-established safety profile even after being administered to millions of people over the course of the pandemic, the FDA said.
In addition to the human data from the BA.1 shots, the approval was also based on animal testing of the BA.5 boosters, Marks said. In June, Pfizer also submitted data to the FDA’s Independent Vaccine Advisory Committee showing that the Omicron BA.5 bivalent syringes increased antibodies in mice that protect against infection by about 2.6-fold compared to the original vaccine elevated.
Marks said the FDA used the same approval process that it has relied on in the past for switching strains in flu vaccines.
“We’re pretty confident that or what we have is very similar to the situation that we’ve done in the past with influenza mutations where we’re not conducting clinical trials for them in the United States,” Marks said. “We know from how the vaccine works and from the data we have that we can predict how well the vaccine will work.”
However, some infectious disease and vaccine experts say the FDA should have waited for human data from the BA.5 shots before approving them. dr Paul Offit, a member of the FDA’s advisory committee, said data based on mouse studies are insufficient to warrant approval of the new boosters.
“You have to show some evidence in people that the immune response you get with the bivalent vaccine is clearly better, and that data hasn’t been presented,” said Offit, an infectious disease and vaccines expert at Children’s Hospital of Philadelphia.
“You can’t ask millions of people to get this booster dose without some human data showing that you have a dramatic increase in neutralizing antibodies against the BA.4/BA.5 strains compared to the ancestral type booster.” Offit said, referring to the currently approved footage based on the version of Covid that surfaced in China more than two years ago.
Michael Osterholm, a leading epidemiologist and director of the Center for Infectious Disease Research and Policy at the University of Minnesota, also said more data needs to be presented on how the BA.5 vaccines perform in humans.
“It’s not that I don’t think it could work,” Osterholm said. “But I think we need the data first to show that the immune response to this vaccine is equal to or better than what we already have.”
But CDC Director Dr. Rochelle Walensky said in a radio interview that waiting longer for human data from the BA.5 recordings could mean that by the time a new variant emerges, the boosters will be out of date. Walensky said the vaccine formula change is small and should not affect safety.
“It’s always about too slow versus too fast,” Walensky said in a radio interview with Conversations on Health Care. “One of the challenges is waiting for that data to show up in human data […] we will use a vaccine that I would consider potentially outdated.”
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