As researchers learn more about the Omicron variant of COVID-19, some say that booster shots are looking like an increasingly good idea to help fight the pandemic.
“If there was no Omicron in the picture, I think that two doses would have been sufficient for us,” said Sabina Vohra-Miller, founder of Unambiguous Science, a health information organization, although health authorities “strongly” recommend Canadians 50 and older receive the booster to protect against Delta.
“Now that Omicron is in the picture, making sure that Canadians are protected against this variant is going to be important.”
The tipping point is a set of new studies that seem to show that the Omicron variant is better able to evade the protection provided by two doses than previous COVID-19 variants.
On Wednesday, in the first official statement from vaccine manufacturers on the likely efficacy of their shot against Omicron, BioNTech and Pfizer said that two vaccine doses resulted in significantly lower neutralizing antibodies but that a third dose of their vaccine increased the neutralizing antibodies by a factor of 25.
Blood obtained from people that had their third booster shot a month ago neutralized the Omicron variant about as effectively as blood after two doses fought off the original virus first identified in China, the companies said.
Meanwhile, a preliminary study published by researchers at the Africa Health Research Institute in South Africa on Tuesday also said Omicron could partially evade protection from two doses of the Pfizer/BioNTech vaccine and suggested a third shot might help fend off infection. The study has not been peer-reviewed.
There is no significant data yet on how vaccines from Moderna, Johnson & Johnson and other drugmakers hold up against the new variant but they are expected to release their own data within weeks.
Canada’s National Advisory Committee on Immunization (NACI) said last week that all adults may be offered a booster shot of vaccine, citing evidence that suggests that protection from SARS-CoV-2 infection decreases over time following two doses of the vaccine.
Does Omicron strengthen the case for boosters?
Adding new variants to the mix strengthens the argument for boosters, said Jason Kindrachuk, an assistant professor and Canada Research Chair in emerging viruses at the University of Manitoba.
“Not only are we seeing what happens normally for us in regards to antibodies waning, but we also have to appreciate that the virus has changed,” he said.
“I think what you’re seeing is certainly more of a call to arms saying we need to get third doses out. This is important for us to be able to deal with a potential onslaught of Omicron and certainly be in the ready if we are going to potentially see that.”
New real-world data from Denmark suggests that many people who have already received two doses of vaccine are being infected with Omicron, and the country has reimposed some restrictions to deal with a renewed outbreak of COVID-19. South African scientists have also reported an apparent drop in immunity with Omicron.
Vohra-Miller noted that the studies on the Pfizer vaccine contain some good news for people who have two doses. While neutralizing antibodies do seem to be affected by Omicron, she said, that’s not the whole picture of immunity.
“The studies also show — and this is the good news part — that T-cells are largely unimpacted, which means that even with two doses of Pfizer, we will still see protection from severe illness. So that is fantastic news,” she said.
This is helpful, Kindrachuk said, but it still means that people could get infected and pass the virus along to others.
“That’s a concern for us because we’re in this period of time where certainly we do not have 100 per cent immunity within our populations,” he said, meaning that unvaccinated people or people with weakened immune systems could still be at risk of severe infection.
More data needed
Omar Khan, a professor of biomedical engineering and immunology at the University of Toronto, said we need more information before deciding whether third doses are really needed.
“Part of the information that’s driving the conversation around meeting a third dose is whether or not our current level of vaccination protects us against severe disease, and we still have to understand this a bit more,” he said.
Speaking at a press conference Wednesday, Dr. Soumya Swaminathan, chief scientist for the World Health Organization, said that it was “premature” to conclude that third doses would be required to deal with the Omicron variant, particularly based on these small studies.
“There’s still a lot of work to be done and then of course, it’s only looking at one element, just the neutralizing antibodies, and we really haven’t got information on the effectiveness,” she said.
It’s also possible that we may just want to update the vaccine rather than give a booster dose with the same formulation, Khan said. Pfizer said Wednesday that they can do this by March 2022 if needed.
Booster doses might be helpful to fight the pandemic, said Dr. Kate O’Brien, director of immunization, vaccines and biologicals with the WHO, but they aren’t the biggest element.
“No matter which way you look at it, primary doses always outperform booster doses for people who are at risk,” she said.
“The primary attention here has to be on assuring that everybody who has not yet had a primary series of vaccination has access to that vaccine and gets vaccinated.”
— with files from Global News’ Jamie Mauracher and Reuters