The data is encouraging because it shows that the bivalent booster shots, which were updated to match the BA.4 and BA.5 versions of the omicron variant and began to roll out in September, are providing protection against newer coronavirus variants ahead of a possible winter surge of cases.
Moderna also said a preliminary analysis with a small number of subjects showed that the antibodies generated by the bivalent booster lost some potency against the challenging and rapidly growing BQ.1.1 subvariant — but could still block it. BQ.1.1 makes up about a quarter of the cases in the United States, according to the Centers for Disease Control and Prevention.
“Evolution is a dangerous thing to bet against. The virus keeps surprising us, and we need to be ready to update the vaccine,” said Stephen Hoge, Moderna’s president. But he added that he was encouraged by the high antibody levels induced by the booster shot as the country heads into winter.
“I think we’re optimistic this BA.4/BA.5-containing bivalent is going to be sufficient to get us through,” Hoge said.
Moderna’s announcement will intrigue scientists thinking about future booster strategies because the makers of both messenger RNA coronavirus vaccines have now presented convergent results showing their bivalent shots trigger a stronger response than their original formulations.
But the news is somewhat of an artificial comparison to the general public because those original boosters are no longer available. The decision to switch was made over the summer to ensure enough supply to vaccinate people with the updated shots ahead of a potential winter surge of cases.
It is also unclear whether the data will help ignite public interest in the boosters. Only about 10 percent of people 5 and older in the United States have gotten a bivalent booster, according to CDC data.
To measure the effect of the additional shot, scientists compared the virus-blocking antibodies in the blood of 511 people, before and after the bivalent booster or the original one. What these kinds of laboratory experiments cannot predict is how well or how long the higher antibody levels will protect people against infections or severe illness. Most scientists expect the boosters will help shore up protection against the worst outcomes but will not provide as robust protection against infections.
Moderna reported that its bivalent booster created five to six times the level of antibodies compared with the older booster. That is a stronger advantage than the effects of a previous bivalent booster tuned to fight the BA.1 variant. But some scientists have questioned whether differences between the two groups of people that received each type of shot could be partially responsible for some of the advantage.
By contrast, Novavax, a latecomer in the vaccine race, presented data last week suggesting that a bivalent booster of its shot that included the omicron BA.1 subvariant did not offer an advantage over its original booster.
The company did not present data on a BA.4/BA.5-containing bivalent vaccine, but argued that its original shot could continue to offer protection, instead of updating the formula. It is unclear why there are divergent results. Novavax’s chief medical officer, Filip Dubovsky, said last week that the company’s shot may induce a broader response to the variants, which is then strengthened by repeated boosts of the older formulation. Unlike the widely used messenger RNA vaccines from Pfizer-BioNTech and Moderna, the Novavax shot is a protein-based vaccine with an added substance called an adjuvant that’s designed to rev the immune system.
Novavax has said it could update its shot if required by regulatory agencies.
“We’re kind of ready to respond to whatever is required,” Dubovsky said. “But we actually think we have a case that sticking with what we have now, and appears to be working now, is the way to go into the future.”