Developing a booster vaccine that offers protection not only against known variants of COVID-19, but also against variants that have yet to emerge, has become the next frontier for the pharmaceutical industry.
This has become the million-dollar question, as Omicron and its growing family of subvariants have dealt a heavy blow to the protection offered by existing vaccines from Pfizer-BioNTech and Moderna.
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Drugmakers, along with outside researchers and government scientists, discussed the topic at a meeting of the World Vaccine Congress in Washington DC on Thursday.
All agree that vaccines need to be updated to ensure they can continue to provide protection against serious diseases, but there is not yet a broad consensus on the best approach to take.
The most popular idea floated was to develop a pan-coronavirus vaccine – a vaccine that could protect against the full spectrum of strains of the virus, known and unknown.
The coronavirus that causes COVID-19 is part of a family of coronaviruses called beta-coronaviruses. The coronaviruses that caused SARS and MERS are also part of this family.
But beta-coronaviruses are just one branch of the larger coronavirus family tree. There are also alpha-coronaviruses, gamma-coronaviruses and delta-coronaviruses.
A pan-coronavirus vaccine would essentially target the trunk of the tree, providing protection against all branches.
Still, a pan-coronavirus could be years away. A similar flu vaccine has yet to be successfully developed.
Such a vaccine could offer “benefits in terms of sustainability and scale,” Kayvon Modjarrad, vaccine expert and director of Walter Reed’s infectious disease branch, said Thursday during a panel discussion on the topic.
Modjarrad, along with his colleagues at Walter Reed, is working on the development of a pan-coronavirus vaccine.
A preclinical study published in December found that the vaccine protected rhesus macaques against disease caused by the original strain of coronavirus and produced antibody responses against variants of concern.
Human trials are currently underway.
The pan-coronavirus vaccine is a different approach than what Pfizer and Moderna are currently pursuing.
Both companies are currently conducting clinical trials testing variant-specific or bivalent vaccines, which would target the dominant circulating strain(s).
Moderna, in particular, said its ideal fall vaccine candidate would be a bivalent vaccine that targets the omicron variant as well as the original strain of coronavirus in one shot.
But with new, often more contagious versions of the coronavirus emerging every couple of months, experts argued at the conference that this approach may not be a sustainable long-term strategy.
Instead, scientists should focus on developing a vaccine that can protect against a wide variety of coronaviruses, regardless of which variant may arise.
While it’s a tantalizing idea, some experts have said the public may still need to temper their expectations of the kinds of protection they want from pan-coronavirus.
Existing mRNA vaccines still provide a high level of protection against serious diseases, for example, but it has become apparent that their protection against infection wanes over time.
Long way to go
We can’t just say “we’re going to develop a pan-coronavirus that protects against infection,” In-Kyu Yoon, acting director of the Coalition for Epidemic Preparedness Innovations, told colleagues. “It’s just too unrealistic right now.”
Protection against infection comes from high levels of antibodies, but these tend to decline after several months. But other parts of the immune system, such as T cells, can persist for years.
Although they don’t act as quickly as antibodies, they appear after an infection to prevent serious illness.
And if and when such a vaccine is developed, the technology behind the new vaccine should still be simple enough for manufacturers to produce at scale.
Pfizer and Moderna’s mRNA injections were hailed by most doctors, researchers and scientists, in part because they could be tested and manufactured in months, compared to traditional vaccines, which can take years.
But the technology behind mRNA vaccines is much newer, meaning many facilities lack the capabilities to produce them. A more traditional vaccine, on the other hand, might be easier to scale.
It won’t work if the shot “can’t be reproducibly made,” said Sriram Sathyanarayanan, chief scientific officer of biotech company Codiak BioSciences. “We have to keep the construction simple enough that we can manufacture.”
And the new vaccine cannot be made without one essential resource: money.
“You always have to have incentives for manufacturers to invest in building ready stock,” Maria Bottazzi, co-director of the Texas Children’s Hospital Center for Vaccine Development at Baylor College of Medicine in Houston.
Bottazzi helped develop another COVID vaccine that has been licensed in India and uses older vaccine technology.
Scientists can “create the big tech but we have to see how it can be funded,” Bottazzi said.
Modjarrad, of Walter Reed, said the vaccine development could mirror Operation Warp Speed, the public-private initiative that helped create the current Covid vaccines from Pfizer and Moderna.
The strategy could prompt drugmakers to develop injections for variants and other threats that “don’t quite exist yet,” he said.