A woman receives a booster dose of the Moderna coronavirus disease (COVID-19) vaccine at a vaccination center in Antwerp, Belgium, February 1, 2022.
Johanna Geron | Reuters
On Thursday, the U.S. Food and Drug Administration’s Independent Advisory Panel recommended who updated Covid plans for fall and winter target one of the XBB variants, which are now the dominant strains of the virus nationwide.
The committee voted unanimously that the updated jabs should be monovalent – meaning they are designed to protect against a variant of Covid.
Those XBB Strains are descendants of the omicron variant, which spiked cases to record highs early last year. They are among the most immuno-evasive strains to date.
But some advisers have expressed concern about the idea of periodically updating shots to target XBB variants after this fall, noting that it is unclear whether the composition of the vaccine will require a seasonal update.
“I don’t know yet if it’s a seasonal virus,” said Henry Bernstein, a pediatrician at Cohen Children’s Medical Center. “I agree that it seems like all the stars are aligning for a monovalent vaccine rather than a bivalent product. It’s not clear to me, from a public health perspective, how much the complexity will be mitigated as we try to move forward with this.”
The FDA generally follows the advice of its advisory committees, but is not required to do so. It’s unclear when the agency will make a final decision on strain selection.
There is also uncertainty about the age groups that the FDA and CDC advise to receive the updated pictures this fall.
But the panel’s recommendation is already a victory for vaccine makers Pfizer, Moderna and Novavax – all of which evaluated and developed versions of their respective vaccines targeting XBB.1.5 and other variants in circulation before the meeting.
These companies will likely deliver their updated vaccines in time for the fall, when the United States is expected to transfer vaccine distribution to the private sector. This means that vaccine makers will start selling their new Covid vaccines directly to healthcare providers and compete for commercial market share.
The panel’s recommendation coincides with a broader shift in how the pandemic is affecting the country and the world at large.
But Dr Peter Marks, head of the FDA’s vaccines division, said the agency was concerned the United States could have another wave of Covid “at a time when the virus was still evolving, immunity population has declined further and we are moving inland for the winter.”
Updated Covid vaccines that are periodically updated to target a high-circulation variant will restore protective immunity against the virus, said Dr. David Kaslow, senior official in the FDA’s vaccines division.
This is a similar approach to how strains are selected for annual flu vaccine. Researchers are evaluating the circulating strains of the virus and estimating which will be most prevalent during the coming fall and winter.
But it’s unclear how many Americans will roll up their sleeves to snap the updated snaps later this year.
Just about 17% of the US population – about 56 million people – have received the reminders from Pfizer and Moderna since their approval in September, according to the Centers for Disease Control and Prevention.
More than 40% of adults aged 65 and over were boosted by these injections, while the rate in young adults and children ranges between 18% and 20%.
These boosters were bivalent, meaning they targeted the original Covid strain and the omicron BA.4 and BA.5 subvariants.
Pfizer, Moderna and Novavax firing data
During the meeting, Pfizer, Moderna, and Novavax presented preliminary data on updated versions of their plans designed to target XBB variants.
Moderna evaluated shots targeting XBB.1.5 and XBB.1.16 – another transmissible omicron descendant – according to Rituparna Das, the company’s vice president of Covid vaccines.
Data from preclinical trials in mice suggests that a monovalent vaccine targeting XBB.1.5 produces a more robust immune response against currently circulating XBB variants than the licensed bivalent vaccine targeting BA.4 and BA.5, according to Das.
She added that clinical trial data on more than 100 people similarly demonstrates that the monovalent XBB.1.5 vaccine produces protective antibodies against all XBB variants. All trial participants had already received four doses of the Covid vaccine.
Das said complete protection against XBB strains is likely due to at least single mutations between the variants, meaning they are similar in composition.
There are only three unique mutations between the XBB.1.5 and XBB.1.16 variants, according to Darin Edwards, manager of Moderna’s Covid vaccine program. In comparison, there are 28 mutations between omicron BA.4 and BA.5.
That means the immune response an updated shot produces against XBB variants will likely be similar regardless of the specific variant it targets, Edwards said.
Pfizer also presented the first trial data indicating that a monovalent vaccine targeting an XBB variant provides enhanced immune responses against the XBB family.
The company provided specific timelines for delivery of an updated vaccine, depending on the strain selected by the FDA.
Pfizer will be able to deliver a monovalent shot targeting XBB.1.5 by July and a jab targeting XBB.1.16 by August, according to Kena Swanson, the company’s principal principal scientist.
Pfizer won’t be able to distribute a new vaccine until October if the FDA chooses a completely different strain, Swanson said.
Novavax did not provide a specific timeline for delivery of a shot targeting XBB.1.5, but noted that an XBB.1.16 shot would take eight more weeks.
Novavax unveiled preclinical trial data indicating that monovalent vaccines targeting XBB.1.5 and XBB.1.16 elicit higher immune responses against XBB subvariants than bivalent vaccines.
The data also demonstrates that an injection of XBB.1.5 produces antibodies that prevent XBB.2.3 from binding to and infecting human cells, according to Dr. Filip Dubovsky, Chief Medical Officer of Novavax.
Dubovsky said that the test results support the use of a single-purpose XBB.1.5 shot in the fall.
The vaccine works differently from messenger RNA vaccines from Pfizer and Moderna, but achieves the same result: teaching your body to fight Covid.