Preliminary data released by the company on Wednesday showed that its omicron-targeting coronavirus booster candidate produced 1.75 times as many neutralizing antibodies against the version of omicron that circulated over the winter, known as BA.1, compared with its existing vaccine.
But the omicron variant has mutated so quickly that several new subvariants have emerged that are even better at evading the immune system’s defenses. Two of those, known as BA.4 and BA.5, are now responsible for 13 percent of new coronavirus cases in the United States, the Centers for Disease Control and Prevention said in new estimates. It is unclear whether BA.4 and BA.5 will become dominant in the coming months or whether existing immunity in the population from infections and vaccinations will curb their spread.
Biden administration officials have said they are preparing for a fall and winter wave that could see 100 million coronavirus infections and a potentially significant number of deaths, driven by omicron subvariants. That makes it even more critical that more effective vaccines are available, particularly to protect the elderly and most vulnerable.
Moderna executives said on a call Wednesday that they are confident the updated vaccine would still provide additional protection against newer omicron subvariants, even though researchers tested its booster dose against BA.1. Even if the updated booster provides less protection against later omicron subvariants than against BA.1, it will probably still be more effective against them than the company’s existing booster, Moderna President Stephen Hoge said.
“We’re pretty confident this vaccine is going to provide a benefit even against the family of omicron subvariants,” Hoge said on a briefing call with reporters.
Soon after the omicron variant was identified in South Africa late last year, Modern said it was developing shots specifically designed to fight the variant. Pfizer and BioNTech announced the same plan, although they have not yet released data on their updated vaccine.
Data from the recent clinical trial, which involved 437 participants, showed that Moderna’s omicron-targeting booster would probably provide longer-lasting protection against variants a month later, compared with earlier versions of its coronavirus vaccine, Moderna said.
The booster “was generally well-tolerated,” with side effects comparable to those from earlier boosters, the company said.
The White House for several months has pressed Congress for more than $20 billion for the coronavirus response. Lawmakers have yet to approve new funding.
The official count of new daily coronavirus infections is slowly climbing in the United States, although the actual numbers are believed to be far higher because so many people are testing themselves at home. The country recorded a 38 percent uptick in new cases during the past week, according to figures compiled by The Washington Post, as protection from booster shots and previous infections wanes and more people go about their lives without masks.
Globally, new coronavirus cases are still declining after the omicron variant triggered tens of millions of new cases worldwide, driving up infections during the winter.