Moderna announced preliminary findings on an updated coronavirus vaccine targeting the Omicron variant on Wednesday, calling it “our lead candidate” for a fall booster shot in the United States.
The researchers at the company tested a booster dose that combined the original vaccine with one that was specifically targeted against Omicron, the variant that became dominant last winter. They discovered that the combination produced 1.75 times the level of neutralizing antibodies against Omicron as the existing Moderna vaccine did alone in people with no history of coronavirus infection.
While those findings appear to be encouraging on the surface, many experts are concerned that the virus is evolving so quickly that it is outpacing vaccine development — at least as long as the United States relies on human clinical trials.
The updated vaccine produced a significantly stronger immune response against Omicron than the existing vaccine a month after the booster shot, according to Moderna’s new findings from a clinical trial involving 814 volunteers. The booster shots came after three doses of Moderna’s vaccine.
However, Omicron has been producing subvariants for months, and some vaccine experts believe that what matters now is how well a new booster formulation protects against the most recent subvariants, BA.4 and BA.5, rather than Omicron itself. These two subvariants, which were discovered in South Africa earlier this year, now account for 13% of new cases in the United States and are rapidly spreading. According to some estimates, they could outcompete the two other Omicron subvariants, BA.2 and BA.2.12.1, within a month.
However, he stated that a very small sample size, combined with isolated other studies, suggested that the levels of neutralizing antibodies elicited by the updated vaccine were two to threefold lower against the BA.4 and BA.5 subvariants when compared to Omicron.
The newest subvariants appear to spread faster than previous versions of Omicron and may be better at evading immune system defenses. It is unknown if they cause more severe disease. Dr. Anthony S. Fauci, the White House’s chief medical adviser, said in an interview Tuesday that South Africa had “seen a slight uptick in hospitalizations, but I.C.U. utilization and deaths are really staying stably low.”
In any case, given how quickly the virus mutates, some vaccine experts believe it makes more sense to target the virus’s most recent versions rather than forms of the virus that have already been surpassed or will be soon.
The problem is that Moderna and Pfizer, the makers of the other major coronavirus vaccine in the United States, do not have enough time to conduct additional human clinical trials while also manufacturing shots before the fall, when the Biden administration hopes to offer an updated vaccine to counter what public health experts predict will be a winter surge.
Moderna’s vaccine trial against Omicron began in late February. The participants’ average age was 57. All volunteers had received three doses of Moderna’s existing vaccine — two shots, followed by an eight-month booster dose.
Three and a half months after the first booster, 377 volunteers received a second booster with the existing vaccine, while 437 received the Omicron-specific booster. Both those who had previously been infected with the virus and those who had not had a stronger immune response to the updated booster.
According to Moderna data, those who received the updated booster had a 59 percent higher level of neutralizing antibodies than those who received the existing booster. Antibodies are the body’s first line of defense against coronavirus infection. Other immune responses that protect against Covid-19 disease were not measured because they are far more complex and time-consuming to perform.
Moderna released preliminary findings on a vaccine retooled to combat the Beta variant, which was discovered in late 2020. The company claimed at the time that the combination provided a stronger defense not only against Beta, but also against Delta and Omicron variants. However, officials predicted that an Omicron-specific vaccine would be a better candidate.