With the arrival of spring, the United States is easing out of respiratory virus season, a familiar pattern that has been challenged by Covid-19 for the past four years.
The addition of a novel germ has complicated and expanded respiratory virus season, which was already notoriously difficult to predict. This season had its own unique set of circumstances as public health balanced a significant transition out of the public health emergency with efforts to find a sustainable way forward.
Experts say that focused planning and forecasting efforts helped avoid some of the worst-case scenarios. But there was still a significant number of severe outcomes, and there are still key areas of improvement – especially around vaccination.
“I am grateful that we’re not still in the height of the pandemic, but we saw some really strong, severe respiratory disease season increases, and some groups were incredibly impacted by it,” said Janet Hamilton, executive director of the Council of State and Territorial Epidemiologists.
Significant burden persists
There have been at least 29 million illnesses, 320,000 hospitalizations and 20,000 deaths from flu this season, according to US Centers for Disease Control and Prevention estimates. And the burden from Covid-19 has been about twice as large.
At least 42,000 people have died from Covid-19 since the beginning of September, according to provisional data from the CDC, reaching a peak of more than 2,500 deaths during the week ending January 13. Covid-19 hospitalizations also peaked in early January, with more than 35,000 new admissions during the week ending January 6 and more than 570,000 total hospitalizations since September.
With flu, respiratory syncytial virus (RSV) and “with the addition of a third virus (COVID-19) that can cause severe disease, even an average respiratory season can place significant strain on our healthcare system,” the CDC’s Center for Forecasting Analytics wrote when it released its first outlook for the season in September. It predicted that this respiratory disease season would be similar to the year before — which saw hospitals more full than at any other point in the pandemic — and worse than pre-pandemic years once again.
In developing the seasonal outlook, the Center for Forecasting Analytics identified a number of key variables could have shifted the season’s outlook for the worse, including a new coronavirus variant, a more severe flu season or overlapping peaks for multiple viruses.
The forecasts have held relatively steady throughout the season, in large part because the viruses spared us from these more severe scenarios. But the US still lagged on one key factor that was fully within human control: vaccination rates.
A variable within our control
Only about 23% of US adults and 14% of children have gotten the latest Covid-19 vaccine, according to data from the CDC. And just about half of the population got their flu shot this year, a tick down from recent years.
“The Covid vaccine is a really safe and effective vaccine that’s kind of a miraculous scientific advancement. It’s discouraging to me that so many people seem to be ambivalent or unwilling to get it, and we really need to work on that,” said Dr. Marcus Plescia, chief medical officer for the Association of State and Territorial Health Officials. “This should be a real asset for our society, and people should be taking better advantage of it.”
A complicated set of reasons may have contributed to low vaccination rates this year, experts say – especially for the Covid-19 and RSV vaccines.
The timing for the Covid-19 vaccine was a bit off this season, Plescia said. The latest shot was approved by the US Food and Drug Administration in mid-September, when Covid-19 hospitalizations had already been on the rise for months.
“One of the problems with the Covid vaccine is that it came out kind of late in the process,” he said. “If we had the vaccine approved and available earlier — maybe in the summer — that gives people a little bit longer to become familiar with and take advantage of the recommendations. That might make a difference.”
Shifting perceptions on where people can get vaccinated — and emphasizing the important role that physicians can play in promoting vaccination at doctor’s visits, in particular — could also really lift vaccination rates, Plescia said.
“It’s great that pharmacies are such an easy and efficient and convenient way for people to get vaccinated, but that only works for people who specifically want and seek the vaccine,” he said. “Early in the pandemic, everybody wanted to get vaccinated, so we really leaned heavily on pharmacies. But I think that’s where we’ve lost some ground.”
But there were challenges in accessing vaccines this season, especially at pediatrician offices. People also had trouble finding vaccines at pharmacies early on, running into roadblocks that didn’t exist before the government commercialized the Covid-19 vaccines last year.
“I think we need to shift back to really work with the medical care community on addressing whatever the issues are that may be making it difficult for them to stock the vaccines,” Plescia said. “We need to really make sure that when people are going to see their doctors, particularly people who are vulnerable, that they’re getting these recommendations, they’re having the chance to talk through it with their clinician and work through any concerns or issues.”
The sense of urgency around vaccination also faded as attention on respiratory viruses waned, said Kathleen Hall Jamieson, a professor of communication and director of the University of Pennsylvania’s Annenberg Public Policy Center. Her work has focused on health and science communication, including research on vaccine confidence.
“When people become attentive, they become pretty good at seeking out knowledge, and they’re pretty effective at aligning their behaviors with that knowledge,” she said. “The problem is that most of the time, we’re inattentive to most of these things, and as a result, it takes a lot more effort to get the attention that is required to get the messaging in place and the messaging tied to a behavior.”
Habits have built up around flu vaccination for much of the population in a way that hasn’t developed for Covid-19 vaccines, she said, which is probably why Covid-19 vaccination rates fell so much further.
“Flu vaccination is a habitual behavior. We don’t have that same kind of habitual behavior associated with the Covid vaccine. And when you stop hearing on a regular basis that Covid is a severe problem, it fades to the background in a way that flu does not,” Jamieson said.
“It’s not vaccination hesitancy that you’re measuring. It’s whether or not you incentivize people or prime people by making the risk of the virus season salient enough for them decide if they need a vaccine.”
Minimizing unpredictability, maximizing preparedness
For vaccines and otherwise, focused and effective communication is at the heart of a successful public health response, experts say, especially in a time as unique as this.
“In all the chatter that was going on about the season, we really focused on what mattered the most and what would change the risk profile the most,” said Dylan George, director of the CDC’s Center for Forecasting and Outbreak Analytics.
Ongoing and “vigilant” tracking of these factors helped the forecasts stay “spot-on in terms of helping people know what level of hospitalizations to expect from the big three: Covid, RSV and influenza,” George said.
They “gave more specificity to what it meant to be ready,” which served as a helpful communication tool with state epidemiologists, state health officials and health care systems, he said.
Although flu is known to be seasonal, there’s a lot of variation in the timing and severity each year. And Covid-19 is still revealing its patterns, too.
The CDC launched the Center for Forecasting Analytics about two years ago, and the group’s respiratory virus season outlooks mark a “subtle but powerful shift” in the ways public health can think about the respiratory virus season, George said.
“For infectious diseases that are changing very quickly, we need to be more prospective,” he said. The outlook “was a good addition to help the institution of public health and CDC start looking more forward in how we’re trying to anticipate risks as they are coming at us instead of just getting hit with something and then trying to understand what we’re hit with.”
Coordination and collaboration
Despite elevated levels of disease, hospitals generally avoided large-scale spikes in admissions from respiratory viruses this season.
Even before the pandemic, hospitals would plan for respiratory virus season and the variability that comes with it, and Covid-19 added a few more factors to that equation, said Akin Demehin, senior director of quality and safety policy with the American Hospital Association.
“There’s an ongoing process of assessment, reassessment, planning, flexing up or down depending on what the needs are on the ground,” he said. “Going into this season, I think hospitals and health systems knew there would be some unknowns around the amount of strain that Covid-19 was going to put on the health care system, and certainly rates of vaccination are one of those contributing factors to that uncertainty.”
Still, better vaccination rates could have eased some of that unpredictability and helped keep hospital capacity levels even more stable this season, experts say.
“I think what the Covid-19 pandemic really underscored for everybody in the health care system is just how much the situation on the ground can change and how rapidly it can change,” Demehin said. “We know that [vaccines] are incredibly effective tools in keeping people healthy, keeping them out of the hospital and, ultimately, on taking some pressure off of the health care delivery system when we do experience these annual spikes in respiratory viruses.”
Data collection ramped up significantly during the Covid-19 pandemic, much of which has scaled back since the public health emergency ended about a year ago, in May 2023. The federal government still requires hospitals to report various data points related to Covid-19, but that will end next month.
Experts emphasize that this is just the fourth data point we have to understand the new trajectory of respiratory virus seasons in the US.
“We are one step closer to understanding more about what respiratory season is going to be looking like, generally, but we’re not there yet,” Hamilton said.