Do you need a spring COVID-19 vaccine? Research backs extra round for high-risk groups

New guidelines suggest certain high-risk groups could benefit from having another dose of a COVID-19 vaccine this spring - and more frequent shots in general - while the broader population could be enter‐ ing once-a-year territory, much like an annual flu shot.

Medical experts told CBC News that falling behind on the latest shots can come with health risks, particularly for individuals who are older or immunocompromised.

"Even when the risk of in‐ fection starts to increase, the vaccines still do a really good job at decreasing risk of se‐ vere disease," said McMaster University researcher and im‐ munologist Matthew Miller.

Who needs another COVID shot?

Back in January, Canada's na‐ tional vaccine advisory body set the stage for another round of spring vaccinations. In a statement, the National Advisory Committee on Im‐ munization (NACI) stated that starting in spring 2024, indi‐ viduals at an increased risk of severe COVID may get an ex‐ tra dose of the latest XBB.1.5based vaccines, which better protect against circulating virus variants.

That means:

Adults aged 65 and up. Adult residents of longterm care homes and other congregate living settings for seniors. Anyone six months of age or older who is mod‐ erately to severely im‐ munocompromised.

The various spring recom‐ mendations don't focus on pregnancy, despite research showing clear links between a COVID infection while preg‐ nant, and increased health risks. However, federal guid‐ ance does note that getting vaccinated during pregnancy can protect against serious outcomes.

"Vaccinated people can al‐ so pass antibodies to their baby through the placenta and through breastmilk," that guidance states.

What do the provinces now recommend?

Multiple provinces have started rolling out their own regional guidance based on those early recommenda‐ tions - with a focus on allow‐ ing similar high-risk groups to get another round of vac‐ cinations.

B.C. is set to announce guidance on spring COVID vaccines in early April, offi‐ cials told CBC News, and those recommendations are expected to align with NACI's guidance.

In Manitoba, high-risk in‐ dividuals are already eligible for another dose, provided it's been at least three mon‐ ths since their latest COVID vaccine.

Meanwhile Ontario's latest guidance, released on March 21, stresses that highrisk individuals may get an extra dose during a vaccine campaign set to run between April and June. Eligibility will involve waiting six months af‐ ter someone's last dose or COVID infection.

Having a spring dose "is particularly important for in‐ dividuals at increased risk of severe illness from COVID-19 who did not receive a dose during the Fall 2023 pro‐ gram," the guidance notes.

And in Nova Scotia, the spring campaign will run from March 25 to May 31, al‐ so allowing high-risk individu‐ als to get another dose.

Specific eligibility criteria vary slightly from provinceto-province, so Canadians should check with their pri‐ mary care provider, pharma‐ cist or local public health team for exact guidelines in each area.

WATCH: Age still best de‐ termines when to get next COVID vaccine dose, re‐ search suggests:

Why do the guidelines focus so much on age?

The rationale behind the latest spring guidelines, Miller said, is that someone's age remains one of the greatest risk factors associ‐ ated with severe COVID out‐ comes, including hospitaliza‐ tion, intensive care admis‐ sion and death.

"So that risk starts to shoot up at about 50, but re‐ ally takes off in individuals over the age of 75," he noted.

Canadian data suggests the overwhelming majority of COVID deaths have been among older adults, with nearly 60 per cent of deaths among those aged 80 or old‐ er, and roughly 20 per cent among those aged 70 to 79.

People with compromised immune systems or serious medical conditions are also more vulnerable, Miller ad‐ ded.

Will people always need regular COVID shots?

While the general population may not require shots as fre‐ quently as higher-risk groups, Miller said it's un‐ likely there will be recom‐ mendations any time soon to have a COVID shot less than once a year, given ongoing uncertainty about COVID's trajectory.

"Going forward, I suspect for pragmatic reasons, [COV‐ ID vaccinations] will dovetail with seasonal flu vaccine campaigns, just because it makes the implementation much more straightforward," Miller said.

"And although we haven't seen really strong seasonal trends with SARS-CoV-2 now, I suspect we'll get to a place where it's more seasonal than it has been."

In the meantime, the guidance around COVID shots remains simple at its core: Whenever you're eligi‐ ble to get another dose whether that's once or twice a year - you might as well do it.

What does research say?

One analysis, published in early March in the medical journal Lancet Infectious Dis‐ eases, studied more than 27,000 U.S. patients who

tested positive for SARS-CoV2, the virus behind COVID, between September and De‐ cember 2023.

The team found individu‐ als who had an updated vac‐ cine reduced their risk of se‐ vere illness by close to a third - and the difference was more noticeable in older and immunocompromised indi‐ viduals.

Another American re‐ search team from Stanford University recently shared the results from a modelling simulation looking at the ideal frequency for COVID vaccines.

The study in Nature Com‐ munications suggests that for individuals aged 75 and up, having an annual COVID shot could reduce severe in‐ fections from an estimated 1,400 cases per 100,000 peo‐ ple to around 1,200 cases while bumping to twice a year could cut those cases even further, down to 1,000.

For younger, healthier populations, however, the benefit of regular shots against severe illness was more modest.

The outcome wasn't a sur‐ prise to Stanford researcher Dr. Nathan Lo, an infectious diseases specialist, since old age has consistently been a risk factor for severe COVID.

"It's almost the same pat‐ tern that's been present the entire pandemic," he said. "And I think that's quite strik‐ ing."

More frequent vaccination won't prevent all serious in‐ fections, he added, or per‐ haps even a majority of those infections, which highlights the need for ongoing mitiga‐ tion efforts.