Experts advise against waiting for Omicron-specific vaccines

Dr. Bogoch on rising subvariant cases Infectious disease specialist Dr. Isaac Bogoch discusses the rise of Omicron subvariants and if there will be another COVID-19 wave soon.

Following the emergence of the Omicron COVID-19 variant, several pharmaceutical companies have announced that they will be manufacturing COVID-19 vaccines that specifically target the latest variant of concern.

In January, pharmaceutical giant Pfizer Inc. and its partner, BioNTech, announced that studies were being done to compare its original COVID-19 vaccine with doses designed to match Omicron. At the beginning of the year, Pfizer CEO Albert Bourla said the redesigned vaccine could be ready to launch as soon as March.

Moderna Inc. made a similar announcement, revealing that the company has begun testing its own Omicron-specific vaccine and that clinical data should be available by March as well. Both companies have since reported delays in delivery of either several weeks or months in order to gather more data.

With companies anticipating relatively short turnaround times for developing these variant-specific vaccines, some Canadians may be contemplating whether to wait before getting their booster shot, for example, in favour of one that targets the predominant COVID-19 variant in Canada.

Even with the prospect of an Omicron-specific vaccine, those who have yet to be boosted should get their third dose as soon as possible, said Dr. Lisa Barrett, an infectious disease specialist and professor at Dalhousie University in Halifax.

“People who are eligible for third doses…particularly those who are vulnerable, who work and reside in high-risk settings, [and] those who are around vulnerable people, I would not recommend waiting,” she told CTVNews.ca in a phone interview on Wednesday. “It does still have benefits for that person and their immediate circle.”

The reason for this lies in high levels of COVID-19 transmission that persist in different parts of the country, Barrett said. Additionally, studies show that current vaccines still offer solid protection against the Omicron variant, she said, particularly in preventing hospitalization and death. As a result, Barrett advises Canadians who have yet to get their third jab to schedule an appointment. The same goes for those who have yet to receive any COVID-19 vaccine doses.

“There's a lot of virus around in our communities right now… a lot more virus than these case numbers suggest,” she said. “So it still makes sense to me to go and get the extra dose of the vaccine.”

With a number of provinces now lifting COVID-19 public health restrictions, protection against the virus from vaccines becomes especially important, said Dr. Earl Brown, a University of Ottawa infectious disease specialist and virologist. Reduced regulations around capacity limits, physical distancing, and masking, for example, are likely to result in greater transmission of Omicron and therefore, more infections, he said. For those who are eligible but have yet to receive their primary vaccine course or booster shot, it’s crucial that they consider getting vaccinated as soon as possible, Brown said.

“Omicron is the virus du jour – that’s what we’re facing and we’re facing it now,” he told CTVNews.ca on Wednesday in a phone interview. “A bird in the hand is worth two in the bush. Get something that will give you protection now rather than have the chance of maybe getting something better in the future.”

Additionally, getting a booster shot now does not mean that a person won’t be able to get an Omicron-specific booster shot later if one does become available, said Barrett, pointing to annual flu vaccines as an example. However, experts continue to wait for more clinical data to support the need for a fourth dose among the general population, said Dr. Gerald Evans, chair of Queen's University's infectious diseases division in Kingston, Ont. As for how long people should wait before getting their Omicron-specific vaccine if it becomes available, data is still needed to determine this as well, he said.

“There's a lot of stuff here that really requires us to wait for the evidence and right now, the weight of everything says stick to the standard vaccine,” Evans told CTVNews.ca in a phone interview on Wednesday.

For Evans, it’s a matter of making decisions based on what is known about current vaccines versus what is not known yet, he said. Although not perfect, they still offer a good amount of ongoing protection against Omicron at a population level, said Evans, particularly when three doses are administered.

“There's not a lot of assurance that [an Omicron-specific vaccine] is necessarily going to give you better immunity,” said Evans. “What I know now is that a third dose of the current standard vaccine…continues to provide very good protective immunity if you were to get infected with COVID [and] in protecting you from going to the hospital.”

IS AN OMICRON-SPECIFIC VACCINE NECESSARY?

According to Evans, there’s uncertainty at the moment around whether a vaccine that specifically targets the Omicron variant is necessary for the general population.

“The jury's out on whether we need an Omicron-specific variant vaccine,” he said.

While Pfizer and Moderna have both said they are currently testing their own vaccines meant specifically for Omicron, results have yet to be released. Because of this, it’s not known yet what the add-on benefit from the vaccines will be and for whom, Barrett said. It’s possible that an Omicron-specific vaccine would be beneficial to those who are more vulnerable to severe disease, for example, such as older groups and those who are immunocompromised. But data from clinical trials is still needed to be sure, she said.

“Is the added benefit of changing the spike protein to an Omicron-specific one going to provide enough additional protection to warrant it?” said Barrett. “We don't know that yet. It should, but we don't know for sure.

“Who it's approved for, how it's approved, and what the add-on benefit is will be very, very important to look at as we go forward.”

For vaccine manufacturers, creating a variant-specific vaccine involves substituting the existing spike protein for one that matches that particular COVID-19 variant, Evans said. Targeting this part of the virus helps prevent it from entering cells and causing infection through the production of neutralizing antibodies.

“It's basically the same vaccine we've had, it's just that the mRNA sequence has been changed to match what exists for the Omicron spike protein versus the original variant,” Evans said.

The virus’ spike protein, however, has continued to mutate throughout the pandemic, said Dr. Jason Kindrachuk, a virologist and assistant professor at the University of Manitoba. According to Kindrachuk, chances are the COVID-19 virus will continue to evolve and the world will see yet another variant.

“When we look across what has happened with other variants so far…and ongoing transmission in various areas of the world, in particular those that have received low vaccine coverage, the likelihood is we are going to see another variant that will emerge,” he told CTVNews.ca on Wednesday in a phone interview. “The likelihood that this is the last [COVID-19] variant is quite low.”

As a result, it’s possible that in the time it takes pharmaceutical companies to manufacture an Omicron-specific vaccine, perform preliminary studies, receive approval and distribute doses, a new variant could emerge that would render these efforts useless, Barrett said. It could take companies several months to roll out these vaccines before they get into the arms of Canadians, Evans said.

By targeting one variant in particular, there’s also the risk that a new vaccine won’t be able to provide the same broad, protective benefits against death and hospitalization as current vaccines do, Kindrachuk said.

“If we go down the lines of moving towards very specific vaccines, that may come at the cost of another variant potentially emerging in that timeframe,” he said. “We don't necessarily know whether an Omicron-specific variant vaccine would give us the same type of effect against a new variant. All of this is difficult to predict.”

Both the added benefit of a targeted vaccine in providing durable protection and the likelihood of the Omicron variant sticking around long enough for a targeted vaccine to be useful must be taken into consideration when determining whether an Omicron-specific vaccine is necessary, said Barrett. These factors, however, remain difficult to assess, she said.

“It's not quite clear yet whether rolling out broad-scale, huge, population-based Omicron-specific vaccines is useful right now,” she said. “Only time will tell.”

KEEPING AN OPEN MIND

Ultimately, vaccines will need to continue to evolve moving forward and likely go beyond just targeting a single variant, said Barrett, given that the COVID-19 virus itself has continued to change throughout the course of the pandemic.

“While having an Omicron-specific vaccine can be potentially helpful, it may not be the sole and only answer,” she said. “Because the virus is still changing quite a bit, it's not clear how long or how well that's going to work in the long run.”

This is especially the case considering the recent emergence of the Omicron subvariant BA.2, said Barrett. While BA.2 does not appear to cause more severe disease after accounting for common risk factors such as old age, it does seem more transmissible. The subtle differences in its genetic structure, specifically among spike protein mutations, may also have an impact on the effectiveness of variant-specific vaccines being developed, Barrett said.

“It’s likely there's a teeny bit of difference in how well the vaccines will work [but] we don't know that for sure yet,” said Barrett.

It’s key that policy makers and the general public keep an open mind and remain fluid in their responses to the pandemic as it progresses, said Kindrachuk.

“[Viruses] evolve in often unanticipated manners and we have to be able to meet that flexibility of the virus, and that's not easy when you're dealing with random mutations,” he said.

This involves a close observation of data in order to determine what provides the highest level of protective benefits, he said.

“We need to continue to explore every avenue possible, but appreciate that the vaccines we have now may also end up being the vaccines that provide us with the best protection,” said Kindrachuk. “So let's keep our minds open to that prospect.”

With files from The Associated Press and Reuters.