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If you were confused by the latest announcement about second booster shots in British Columbia, you aren’t alone.

Public health officials said July 8 that most adults under 70 won’t be eligible for a fourth shot until the fall.

That’s when a new vaccine offering greater protection against the Omicron COVID variants is expected to be approved and available in B.C.

Right now, B.C. is only officially recommending second boosters for older and extremely vulnerable people.

But Health Minister Adrian Dix said that those over 18 wishing to receive a second booster before then could call Immunize BC to book a shot, provided it’s been six months since their first booster shot.

These people would then likely need to wait six months before receiving the new bivalent Omicron booster when it is available, Dix said.

“Things are not simple with COVID-19. The recommendation hasn’t changed, but we wanted to be flexible,” Dr. Martin Lavoie, acting provincial health officer, told The Tyee in an interview Friday.

Other provinces such as Ontario, Quebec and Alberta have already opened up eligibility to people 18 and over, with intervals as low as four months since the first booster.

This follows current national guidance, which also suggests a second booster can be given as soon as three months after the first if there is “high epidemiological risk.”

In the week since the announcement, questions about when, why and how to get a second booster have flooded in as a rise in hospitalizations signals the seventh pandemic wave is here.

And while official guidance asks people to wait until the fall for the new vaccine variety, two experts agreed getting fourth shots as soon as you’re able is the best way to avoid a serious illness from new subvariants.

“As soon as you’re eligible, I would say they should do it,” said Dr. Brian Conway, medical director at the Vancouver Infectious Diseases Centre.

“If you got your third shot more than four months ago, we should be looking at giving you your fourth shot now.”

Here’s what Conway and retired emergency physician Dr. Lyne Filiatrault say you should know before you decide.

Boosters renew protection against serious outcomes

Boosters are essential to prevent serious outcomes from the Omicron family of variants in particular.

A third shot provides about 76.5-per-cent protection against hospitalization with Omicron compared to about 40 per cent with just two doses.

“People who don’t have the entire recommended series are really underprotected right now,” Lavoie said.

Only about 59 per cent of British Columbians have received their first booster shots. About 64 per cent of people eligible for their second booster have taken it, only about five per cent of the population.

And while fourth doses provide more marginal boosts in protection, they will be important for keeping people out of the hospital.

In a study of long-term residents in Ontario, second boosters provided 86-per-cent protection against serious outcomes from Omicron, compared to 77-per-cent protection from a third shot more than three months ago.

Serious outcomes like hospitalization, ICU admission or death should be the focus of a fourth dose campaign, Filiatrault said. “The health-care system is burdened as it is.”

Protection from vaccines and infections wanes

The vaccines available in Canada provide excellent protection against serious outcomes from COVID-19, but that does lessen over time.

Protection from hospitalization after three doses is about 91 per cent in the first two months and drops to about 78 per cent three to four months after the booster.

That means people boosted in the winter and spring are already at higher risk, especially without widespread protective measures like indoor masking.

And with Omicron, their protection from mild to moderate infection drops much more quickly than it did with previous variants.

Protection doesn’t drop off a cliff at any point, Lavoie noted. “For someone who is vaccinated, it never drops to zero.”

A recent study suggests protection from hospitalization and death with two doses, boosters or previous infection remains over 70 per cent after six months.

But a recent study suggests the BA4 and BA5 COVID variants driving the current infection wave are much more easily able to evade vaccine protection, reinfecting people as soon as 23 days after their initial infection.

And new evidence that each subsequent infection damages the immune response and does not lead to durable protection is cause for concern, even if someone had an Omicron infection earlier this year.

“Omicron really changed everything,” Filiatrault said.

New vaccines are coming, but timelines could change

Lavoie and Dix encouraged British Columbians to wait for new vaccines that are more targeted towards the Omicron family of variants, which they expect to be available this fall.

These boosters, known as bivalent vaccines, include half mRNA targeted at the original strain of the coronavirus and half mRNA targeted towards the Omicron family.

Clinical trial data submitted by Pfizer and Moderna show they provide stronger protection against severe infection and outcomes compared to original, “monovalent” booster shots, but this data was based on BA1 and BA2 which are receding as BA5 dominates.

Moderna has submitted its bivalent vaccine to Health Canada for approval, which could take several weeks.

Lavoie said public health is hoping for an August approval allowing B.C. to aim at providing the new vaccines in September.

But supply is also an issue. If there are delays, as Canada saw in spring 2021, it could be months until the vaccine is available to younger, otherwise healthy adults, time during which their previous protection will continue to wane.

Filiatrault said there are too many unknowns about when and how well the bivalent boosters will work to wait for them.

With a seventh wave potentially sending 60 people in B.C. to hospital per day at its peak next month, imperfect protection now is much more valuable than waiting for better protection in the future, she said.

“Now is time to protect against severe outcomes for people that have been waiting more than six months from their booster,” said Filiatrault.

Future variants and waves are impossible to predict

Lavoie and Dix said their recommended fall campaign will coincide with respiratory illness season, when airborne pathogens like COVID-19, the cold and flu tend to circulate more due to temperature, humidity and people gathering more closely indoors.

But COVID-19 waves have not been solely seasonal because the virus is not yet endemic, Lavoie acknowledged. “We’re not there yet.”

Filiatrault said it’s impossible to anticipate what new variants will come and how they will be affected by current vaccines. More universal vaccines, aimed at parts of the virus which tend not to mutate as much, are still being developed.

But we do know how protection against severe illness and death wanes and vaccination schedules can be based on that, she said.

And with the virus mutating constantly as transmission remains high, there is no guarantee Omicron BA4 or BA5 will still be dominant when bivalent vaccines become available in the fall.

There could be a new sibling or an entirely new variant, Filitrault said. “It’s a moving target.”

Lavoie noted that the bivalent vaccines would be effective against future Omicron siblings, but that a whole new variant could present a new challenge. “There is a lot we don’t know.”

Conway said he expects the province to evolve its strategy, as it has in previous waves, as the virus changes.

He doesn’t think people who receive a fourth shot now will necessarily have to wait six more months for the bivalent vaccine as new evidence and variants arise.

“I could absolutely see that window shrinking,” Conway said. Lavoie agreed it was possible.

In the absence of broader public health measures, Filiatrault and Conway agree that individuals should take every possible step to protect themselves from serious illness.

That means first and foremost getting the entire recommended series of vaccines, which are two doses and a booster for anyone 12 and over.

And “if you have access to a fourth shot right now, please go get your fourth shot of the ancestral vaccine, because this is going to bring you to the next shot you get, which will be bivalent,” said Conway.

As well, Filiatrault wants to see broader protections like masking and better ventilation brought in while pan-coronavirus vaccines are developed to protect against these and future variants.

“We are to blame by removing all protections and relying on only one slice of the pie,” she said. “By not vaccinating poorer countries and allowing it to circulate unencumbered, we are right now pushing the virus to evolve to evade our vaccines."

— This story was originally published by The Tyee.

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