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 subvariants that make up about 95 percent of US cases.
A briefing paper outlines that Pfizer, Moderna and Novaxa should prioritize vaccine formulation tinkering to target specific XBB sublines 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 meet Thursday to determine which strain will be targeted by the next generation of Covid vaccines, similar to the method used to determine which flu strain will receive the annual will get the flu shot. goal in the coming 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 last September.
But health officials from the FDA and World Health Organization believe the next generation of Covid injections should be monovalent, targeting a specific subline like XBB that currently dominates the spread in the US.
The recommendation for a monovalent vaccine targeting specific XBB-omicron subvariants comes nearly a year after a bivalent vaccine targeting more than one variant debuted and met with moderate public enthusiasm
The FDA’s recommendation comes nearly a month after a World Health Organization advisory group said the current crop of shots should be updated to target the currently dominant strains of XBB.
Matching the vaccine to the circulating variety is crucial to provide the best possible protection against serious disease, but not necessarily to prevent infection in the first place.
Once the new strain is selected, vaccine manufacturers including Pfizer-BioNTech, Moderna and Novavax will need to update the formulations of their injections.
Those companies have already begun reformulating their vaccines to better target the XBB.1.5 omicron subvariant, given its ominous nickname of “Kraken,” as in the multi-tentacled sea monster of Scandinavian lore.
The next iteration of Covid shots will be monovalent, meaning they only target one species, such as XBB.1.5 or another omicron subtype.
The divalent booster shot unveiled last year targeted the Omicron BA.4/5 strain and original virus variants, but suggested a subsequent study that the protection afforded by the omicron-specific booster provided only slightly better neutralizing antibody protection against the XBB and XBB.1 variant than three doses of the original vaccine.
Enthusiasm for last year’s bivalent boost was lukewarm at best, with only about 17 percent of Americans hands-on for one.
One of the biggest benefits of going through a three-year viral pandemic was that a pathogen can mutate dramatically over time, become more transmissible or evade vaccines.
This was confirmed during the arrival of the devastating Omicron variant when it became clear that it was the original iteration of the vaccine offered less protection against symptomatic disease.
The FDA officials said: ‘[The coronavirus] evolution is complex and remains unpredictable. There is no evidence that the evolution of SARS-CoV-2 is slowing, although immunity seems to mitigate serious clinical outcomes.
“Intrinsic viral factors, including mutation rate and recombination potential, generate opportunities for increased transmissibility and host adaptation. At the same time, the host’s immune responses and other factors contribute to the selection of variants.’
The XBB.1.5 strain, a descendant of the XBB-omicron subvariant (itself a combination of two lines descended from the BA.2 subvariant) was described earlier this year as the most transmissible to date.
The XBB.1.5 strain was even unofficially nicknamed “Kraken,” as in the huge 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 about 1.6, meaning that each person infected by this subvariant will, on average, about 1.6 other people.
Virologists have also said they use the headline-grabbing names of mythical creatures as a way for laymen to differentiate between the flurry of new variants that would otherwise have to be identified using a confusing array of letters and numbers.