Drugmakers are crafting Covid-19 vaccines that would target more than one strain of the virus, hoping to strengthen the immunization campaign against the pathogen as it evolves.

Researchers at Moderna Inc., Novavax Inc. and the University of Oxford are designing the shots, known as multivalent vaccines, to protect not only against the form of the virus commonly circulating globally but also potentially contagious strains that have emerged or might in the future.

The work belongs to a range of efforts vaccine makers and drug researchers are undertaking to get ahead of variants like the one identified in the United Kingdom, South Africa and Brazil.

Research indicates some vaccines currently in use generate weaker immune responses against the strain found in South Africa in particular, though there isn’t evidence indicating that current vaccines don’t protect against variants.

To be safe, companies are exploring strengthening the protection conferred by existing shots by adding doses, updating the shots or crafting a booster. A multivalent shot is another approach in the works.

Testing multivalent vaccine candidates in people hasn’t started yet. Some companies hope to begin in the spring so that shots can be available for use as early as the summer.

Health experts say the broad-acting shots could make a difference in the pandemic fight by stymieing mutations to the coronavirus that could help it evade existing vaccines before widespread herd immunity is achieved.

“If there are two or three predominant world-wide strains, and infection or immunity to one doesn’t protect against the others, then we may need multivalent vaccines,” said Buddy Creech, director of Vanderbilt University’s vaccine research program.

Multivalent vaccines are a widely used weapon against other viruses, such as measles, mumps and rubella. Some pneumonia vaccines target as many as 23 strains, while most flu shots target four different influenza strains.

To defeat a variety of variants, the vaccines essentially blend together a number of different shots. So long as researchers pick the right combinations, the vaccines should work, though not if the mixture spreads protection too thin, vaccine experts say.

Multivalent vaccines would be especially useful against Covid-19, virologists and vaccine experts say, if scientists are able to predict which mutations might spread, as is done with influenza each year.

“The real question is what’s the virus going to evolve to, and if we knew the answer to that, then we could stop it,” said Dr. Sean Whelan, a virologist at Washington University in St. Louis whose lab is trying to predict important mutations.

Companies began pursuing multivalent Covid-19 vaccines in recent months as research suggested emerging variants could escape protection from the vaccines currently available.

The companies may prefer to make multivalent Covid-19 vaccines, rather than tailoring shots to various regions of the world with different variants.

Yet multivalent vaccines are more complex to research and manufacture, which can increase company costs and the time it takes to make them, vaccine experts say.

The world-wide market for Covid-19 vaccines would be worth more than $15 billion if annual shots are needed to address waning protection over time and multivalent vaccines are required to head off variants, Bernstein Research estimates.

Moderna, which is developing a vaccine targeting the strain identified in South Africa specifically, is also pursuing a candidate that would combine the variant-focused shot with the company’s vaccine currently in use.

The combination “might ultimately be the best approach,” Moderna President Stephen Hoge said during an earnings call last month. Moderna hasn’t specified when a study would begin for the multivalent candidate.

Novavax, which has a Covid-19 vaccine targeting the original version of the virus in late-stage U.S. testing, plans midyear to begin testing a bivalent vaccine that targets the original version of the virus as well as the variant first identified in South Africa, Dr. Gregory Glenn, the company’s R&D chief, said on a conference call this month.

It settled on this approach after analyzing data from its clinical testing in the U.K., indicating targeting the South African variant would offer protection against other strains, a Novavax spokeswoman said.

University of Oxford researchers are pursuing a multivalent approach that includes targeting strains first identified in Brazil and South Africa, according to AstraZeneca PLC, which licensed the shot to distribute.

Trials could begin this spring with the shot available in the summer, Dr. Mene Pangalos, an AstraZeneca R&D executive, said on a conference call with analysts last month.

Drew Weissman, an immunologist at the University of Pennsylvania whose research contributed to the mRNA technology used by BioNTech SE and Moderna, said his team is working on a multivalent vaccine to cover all current and future variants.

“Nobody wants to be in a position where a variant is suddenly infecting everybody all over again, so people want to have their vaccines ready to go. We haven’t hit that point. So we’ve got time to do this right,” he said in an interview.

Johnson & Johnson has said it is preparing an antigen—the substance that a vaccine relies upon to generate an immune response—that would target the variant that spread in South Africa.

The company, which has a newly authorized Covid-19 vaccine, hasn’t committed to a multivalent shot, but would develop one if a variant escaped protection from the vaccine.

Pfizer Inc., which developed with partner BioNTech the first Covid-19 vaccine authorized in the U.S., is only working on a vaccine targeting the South African variant. Pfizer believes it is sufficient to target just the one strain because it is crowding out other variants, so a multivalent vaccine attacking multiple strains isn’t necessary, said Phil Dormitzer, the drugmaker’s chief scientific officer of viral vaccines.

Yet Dr. Ofer Levy, director of the vaccine program at Boston Children’s Hospital, said multiple variants may circulate simultaneously until one becomes the dominant strain.

This story has been published from a wire agency feed without modifications to the text.

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