Roll up your sleeves: FDA urges Pfizer and other vaccine makers to update Covid jabs by fall to target XBB variants
Federal regulators said this week that new iterations of the Covid vaccine this fall and winter should target highly contagious omicron sub-variants that makeup about 95 percent of US cases.
A briefing document outlines that Pfizer, Moderna and Novaxa must prioritize tinkering with vaccine formulations to target specific XBB sublineages of omicron, either the XBB.1.5, XBB.1.16 or XBB.2.3.
The Food and Drug Administration’s (FDA) expert panel of virologists and vaccine scientists will convene on Thursday to determine which strain will be targeted in the next generation of Covid vaccines, similar to the method used to determine what strain of influenza the annual flu shot will target in the upcoming season.
Covid vaccines have only been reformulated once when a bivalent version based on the original ‘wild type’ strain and the BA.5 Omicron variant was introduced in September of last year.
But health officials at the FDA and the World Health Organization believe that the next generation of Covid shots should be monovalent, which targets one specific sublineage like XBB currently dominating the spread in the US.
The recommendation for a monovalent vaccine that targets specific XBB omicron subvariants comes almost a year after a bivalent vaccine targeting more than one variant was debuted and met with lackluster enthusiasm from the public
The FDA’s recommendation comes nearly a month after an advisory group for the World Health Organization said the current crop of shots should be updated to target the currently dominant XBB strains.
Matching the vaccine to the circulating variant is crucial to providing the best possible protection against severe illness, though not necessarily preventing infection in the first place.
Once the new strain is selected, vaccine manufacturers, including Pfizer-BioNTech, Moderna, and Novavax will have to update the formulations of their shots.
Those companies have already begun reformulating their vaccines to target better the XBB.1.5 omicron subvariant, given the foreboding nickname ‘Kraken’, as in the multi-tentacled sea monster of Scandinavian lore.
The next iteration of Covid shots will be monovalent, meaning they target only one strain, such as XBB.1.5 or another omicron subtype.
The bivalent booster shot unveiled last year targeted the Omicron BA.4/5 strain and original virus variants, but a subsequent study suggested that the protection afforded by the omicron-specific booster produced only slightly better neutralizing antibody protection against the XBB and XBB.1 variant than three doses of the original vaccine.
Enthusiasm for the bivalent boost last year was tepid at best, with only about 17 percent of Americans rolling up their sleeves for one.
One of the biggest takeaways from enduring a three-year viral pandemic was that a pathogen can mutate drastically over time, becoming more transmissible or able to sidestep vaccines.
This was borne out during the advent of the devastating omicron variant when it became clear that the original iteration of the vaccine provided less protection against symptomatic disease.
The FDA officials said: ‘[The coronavirus] evolution is complex and remains unpredictable. There is no indication that SARS-CoV-2 evolution is slowing down, though immunity appears to mitigate severe clinical outcomes.
‘Intrinsic viral factors, including mutation rate and recombination potential, generate possibilities for increased transmissibility and adaptation to the host. At the same time, host immune responses and other factors contribute to the selection of variants.’
The XBB.1.5 strain, a descendant of the XBB omicron sub-variant (itself a combination of two lineages descended from the subvariant BA.2) was described earlier this year as the most transmissible to date.
The XBB.1.5 strain even earned the unofficial nickname ‘Kraken’, as in the enormous mythical multi-tentacled sea monster, citing its rapid spread and ability to evade vaccine protection.
According to researchers at the Fred Hutchinson Cancer Center in Seattle, XBB.1.5 has a reproduction number of around 1.6, meaning that every person infected by this subvariant will go on to infect an average of about 1.6 other people.
Virologists have also said that they use headline-grabbing mythical creatures’ names as a way for laypeople to distinguish between the flurry of new variants that would otherwise have to be identified using a confusing string of letters and numbers.
