Covid-19: Is an ‘Omicron-specific’ vaccine needed? Scientists say it might come too late

As the world stands vexed over whether an Omicron-specific vaccine for the coronavirus disease (Covid-19) is needed, several public health professionals and infectious diseases experts interviewed by Nature magazine have presented different ideas on the matter.

According to medicos and researchers who the journal talked to, it is still unclear if the scientific community even needs to invest a significant amount of its time and efforts behind a vaccine specifically made to counter the highly transmissible Omicron strain of the SARS-CoV-2 coronavirus, given that cases may flatline before the shot is authorised in most places around the world or that the next strain could be radically different from the current one, requiring once again a different vaccine makeup.

The debate: Why is an Omicron-specific vaccine in the works?

The very first of the Covid-19 vaccines were based on the initial SARS-CoV-2 strain first detected in China’s Wuhan. But the coronavirus has undergone multiple mutations since then; the Omicron strain, capable of undergoing frequent transmissions, contains more than 30 mutations in key regions of its genome, thus making it radically different from the initial strain.

Given the change in Omicron’s biology from the original virus’, and the fact that the new strain is on its way to becoming the dominant variant in several countries around the world, researchers put the idea of an updated vaccine makeup on the table.

Moreover, the protection provided by the booster shots is not everlasting. While the UK health security agency says a third dose of the vaccine reduces hospitalisation risk by 92 per cent and the US Centers for Disease Control and Prevention (CDC) says it prevents hospitalisation with 90 per cent effectiveness, everyone agrees that this protection provided by a booster shot also wanes quickly. Studies in the UK have shown that just 10 weeks after a third dose, effectiveness against hospitalisations drops from 92 per cent to 83 per cent.

Notably, a system to update pre-existing vaccines already exists for, say, the influenza virus. The World Health Organization (WHO) has an expert team that meets twice a year to recommend the composition of the next season’s vaccine, making it easier for the health regulators of respective countries to follow through. There are also more than 100 laboratories and five WHO collaborating centres across the globe conducting year-round surveillance, testing thousands of virus samples, and predicting how the next strain of the flu virus will be.

Not an easy decision

However, there are some complications in replicating the influenza vaccine model for the coronavirus, especially in light of the Omicron variant.

Scientists say semiannual flu vaccine composition decisions are possible only because the influenza virus has been here long enough for it to settle into a more-or-less predictable pattern, meaning researchers can typically ‘forecast’ the vaccine makeup for the next strain deriving from previous ones.

However, things have not been so straightforward with the SARS-CoV-2 coronavirus. It has undergone key mutations, some of them radically altering the virus’ biology, making it extremely difficult to predict how the next strain will be.

Although Omicron now makes up more than 98 per cent of the Covid-19 cases in the United States, an ‘Omicron-specific’ vaccine might just come too late to actually be of any use, scientists say, considering the possibility that cases might plummet or a new variant with differing biology might emerge.

Such a vaccine might work against the variant that dominates after Omicron — especially if the virus continues on that genetic trajectory. But no one knows how the virus will evolve.

“All of us should be pretty reticent about predicting what is going to be the best-matched vaccine months from now,” the Nature journal quoted Paul Bieniasz, a virologist at Rockefeller University in New York City.

Just a few months ago, many researchers predicted — logically, but incorrectly — that the next dominant variant to follow Delta would be a virus like Delta. We now know, of course, that Omicron turned out to be completely different.

Even Kanta Subbarao, who chairs the Technical Advisory Group on Covid-19 Vaccine Composition for WHO, said that further discussions are needed on whether to update the composition even though “there is a lot of confidence” in the current vaccines.

“There is a lot of fear that if we make a recommendation to update a vaccine, that people might feel that the existing vaccines are no longer useful”, which isn’t true, Subbarao said. “It’s going to be a difficult message to thread.”

What next?

Some countries have already started offering additional booster doses, but a recent study from Israel showed that while a fourth dose of an mRNA vaccine boosted antibodies, the level was not high enough to prevent Omicron infection.

Meanwhile, Pfizer Inc and BioNTech SE said last week that they started a clinical trial to test a new version of their vaccine specifically designed to target the Omicron variant.

Banking on volunteers in the US, the companies plan to test the immune response generated by the Omicron-based vaccine both as a three-shot regimen in unvaccinated people and as a booster shot for people who already received two doses of their original vaccine.

They are also testing a fourth dose of the current vaccine against a fourth dose of the Omicron-based vaccine in people who received a third dose of the Pfizer/BioNTech vaccine three to six months earlier.

Pfizer said that two doses of the original vaccine may not be sufficient to protect against infection from Omicron, and that protection against hospitalizations and deaths may be waning.

However, the European Medicines Agency (EMA) has said that international regulators want data from clinical studies like the one being done by Pfizer and BioNTech before approval of any new vaccine(s).