Flu Vaccines

FILE - In this Thursday, Jan. 23, 2020, file photo, a patient receives an influenza vaccine in Mesquite, Texas. Amid all the focus on COVID-19 vaccinations, U.S. health experts have another plea: Don’t skip your flu shot. With U.S. schools and businesses reopened, international travel resuming and far less masking this fall, flu is likely to make a comeback.

Colorado had an unprecedentedly mild flu season last year, thanks in large part to the benefit brought by COVID-19 efforts, changes in classrooms and a push to bolster flu vaccinations.

Though it's impossible to predict what this year will bring, health officials said, it's unlikely to be that quiet again.

"There were 34 hospitalizations last year, compared to, I think, 3,500 the year before," said Eric France, the state's chief medical officer. "It's going to be something more like that."

The COVID-19 pandemic has not ended, and there remain patches of Colorado where the measures used to blunt it remain in effect. Many school districts still require masks and social distancing, France said, which will help slow the spread of all respiratory illnesses, from COVID-19 to influenza and RSV.

But unlike late last winter, students are consistently in school, and there's already been unprecedented spikes in RSV hospitalizations, pediatric health officials have said.

The flu season typically begins in October, peaks between late December and February, and begins to peter out in the spring. At this time last year, state health officials were pushing flu vaccinations hard. That was primarily to blunt those 3,500 hospitalizations, which would've come as the state was weathering a COVID-19 surge that landed roughly 2,000 Coloradans in the hospital at once.

Though the flu season will likely not be the same, the push to vaccinate will be similar, France said. That'll include pharmacists' involvement and outreach at food banks, shelters and other, less traditional sites, health officials said.

"I think there will be a lot of messaging to communities not to forget your flu shot," he said. "We all need reminders, and it needs to be in our face. I went to the optometrist last week, and they happened to be giving flu shots there. I got it at the same time."

Judy Shlay of Denver Health said a key difference this year is that the flu and COVID-19 vaccinations can be co-administered, meaning it'll be easier for providers — particularly those in primary care offices, which the state has increasingly leaned upon for inoculations this year — to double-cover patients. 

But there are other, less encouraging key differences, she and France said. For one, children are in school. That's often the setting in which flu is spread: first among students, then back to adults and families, who can then spread it at work or while socializing. What's more, the behavioral changes of 2020 — masking, social distancing, hand washing, less socializing — are not observed as much now as then, Shlay said.

"What we're seeing now and are worried about is the delta variant, it's more infectious, and we're starting boosters for certain classes of people," she said. "People aren't masking as much, you have people socializing more, people not masking as much, and we've seen breakthrough cases with the COVID vaccine." 

Denver Health is pushing flu vaccines in a variety of settings, she continued, but staff "are stretched" between dealing with the COVID-19 pandemic and the ongoing stress associated with it.

What's further unclear is whether the flu season will mirror what the state's already seen with RSV cases. RSV is another respiratory illness that primarily affects — and often hospitalizes — children. It, like the flu and many respiratory diseases, is a winter illness. But Children's Hospital Colorado said in August that it had seen an unprecedented spike in cases and hospitalizations in late summer.

It's not fully clear why, but pediatric officials said it was likely because 2020 was so mild: Children's immunity may have dipped, meaning they were more susceptible this year. That may happen with flu, though predictions — especially with a disease like flu, where the vaccine's efficacy can vary from year to year depending on the dominant strain — are impossible to make.

"There is a concern there," Shlay said. "The Southern Hemisphere" — which health officials monitor as a predictor for how the flu season will appear here — "didn't have a big flu season. That's good, that's how it was last year. If that translates to how things will be, that will be fantastic. But we have to be planning for — people were not exposed last year, people didn't get the flu. This year, if they get exposed, they could have a harder time."