On Saturday morning, I finally rolled up my sleeve for the vaccine I’d been waiting for all summer: my annual flu shot, a technological marvel that I choose to get every fall.
During non-pandemic times, the flu vaccine is a hot fall product that takes a coveted place in the public health spotlight. Of late, however, the shot has been overshadowed by the fame of its COVID-blocking cousins, fueled by debates over boosters and mandates. It’s also been a while since we’ve dealt directly with the flu. Thanks to the infection prevention measures the world took to fight SARS-CoV-2 when the pandemic began, many other respiratory viruses disappeared. Last winter, we essentially had “no flu season at all,” said Florian Krammer, a virologist at the Icahn School of Medicine at Mount Sinai. The human attention span is short; the short sabbatical from the flu could have removed it from our minds at an inopportune time.
An absent virus is not necessarily an extinct virus, and the return of the flu would always be a matter of when, not if. And as the weather cools, experts fear that skipping a sick season could come at a cost if we don’t increase our flu shields again. Immune system can rust and crumble; flu viruses can return to find a host of hosts more vulnerable than before, especially now that kids are back in the classroom and mask boredom continues to balloon across the country. “I’m concerned that we’re not paying attention,” Hana El Sahly, an infectious disease physician and vaccine expert at Baylor College of Medicine, told me. Flu shots are therefore very valuable this year-perhaps more than they’ve been in quite some time.
Concern about a re-emergence of the flu is not new. Back in February, when I first wrote about the lull in flu cases, experts warned that the bugs’ truancy could make them more unpredictable. Flu viruses, already a known threat to our immune system, less easy to spread than SARS-CoV-2, making them easier to eradicate with masks, physical distancing, school closures, and international travel bans, even if compliance was spotty. Cases around the world plummeted. But “nobody expected the flu to go away forever,” Mary Krauland, an infectious disease modeler at the University of Pittsburgh, told me.
Now we’re teetering on the brink of the chilly New Year’s Eve as pandemic restrictions wash and wipe. Many experts suspect that we are partially entering a flu season that is worse than the last because the previous one was so mild. The threshold for an outbreak could very well be lower this year. “I’m probably 60-40: 60 we’ll have a season, 40 we won’t,” Richard Webby, a flu expert at St. Jude Children’s Research Hospital, in Tennessee, told me. “My feeling is that when it comes back there will be a little bit more punch.”
The absence of the flu had positives. It saved healthcare workers, hospitals and the general population a second winter wave of illness, on top of an already overwhelming pandemic. Our non-flu season has also starved host viruses to multiply and change shape and persist. Some experts are hopeful that certain genders may have been squeezed out of existence altogether, or at least come close. That could mean that we will have fewer flu flavors and vaccines in the future, although their disappearance is not yet certain.
But last season also left our sometimes forgetful immune cells without an important annual reminder: Flu viruses do exist and can wreak havoc on the body. Reasonable Good the flu vaccine coverage last winter certainly fueled our bodies’ memories. But without the extra alarms generated by actual illness – which strikes during normal times many millions of people in the United States alone – people’s bodies may not be as tuned as they should be. “You really need the seasonal waves to boost immunity at the population level and prevent major outbreaks,” Helen Chu, a physician and immunologist at the University of Washington, told me.
Infants and young children may be especially vulnerable this year because a greater number of them than usual have never had a flu virus. Schools have reopened, many without mask requirements, adding risks to both children and those who interact with them. “When it comes to the flu,” El Sahly said, “children are the engine of transmission in the community.” A taste of this pattern has already unfolded in the spring and summer with respiratory syncytial virus, another airway-loving pathogen that hits children especially hard. Like flu viruses, RSV nearly evaporated last winter, but around early April, when many COVID-19 restrictions eased, it was able to make its way back into the U.S. population.
Two recent models by Krauland and her colleagues at the University of Pittsburgh, posted in preprint papers last month, point to the toll of missing our annual immune boost. Flu cases and hospitalizations, the studies found, could both experience a bump this year, possibly more than typical seasons — an added burden that the pandemic-ravaged health care system can afford little. That’s especially likely if COVID precautions are getting less and less, or if we’re struck by a particularly contagious strain of flu that our bodies don’t recognize well. Worryingly, other experts pointed out that flu viruses and SARS-CoV-2 can invade even some of the same individuals at once, leading to very serious illnesses in the vulnerable.
These are not obvious conclusions, Kyueun Lee, who led one of the studies, told me. Our social behavior is still not at pre-pandemic levels; even intermittent masking, distancing and the like could put a damper on the upcoming flu campaign. In Australia, a country that countries in the north of the world commonly look at as an epidemic bellwether, flu levels have remained quite low, which could bode well for the United States, Ibukun Kalu, a pediatric infectious disease doctor at Duke, told University, me (although she added that the US approach to COVID containment was “very different” from the Australian one). The number of cases could end between last year’s surprising low and the pre-pandemic norm.
We also have an extraordinarily powerful but underutilized tool in our arsenal: an immunity-boosting vaccine. The flu shot usually only reaches about half of the US population, but Lee thinks it’s essential to increase that percentage this year, as it could help close some of the cracks that COVID restrictions have left in our anti-flu armour. “Getting a flu vaccine this season could be especially important,” Lynnette Brammer, who leads the CDC’s domestic flu surveillance team, wrote in an email. But there is one more catch. Normally, surveillance centers located around the world can many thousands of viral genome sequences to get a good idea of which versions of flu viruses are doing the rounds — which ones may see a resurgence if given the chance. Scientists are mining this wealth of data when selecting species for annual recording. But last winter, that genetic resource dried up. “It’s hard to choose if you don’t have a clear picture of what’s out there,” Krammer told me.
But there were enough data to make an informed decision, experts reassured me. “The match is always a gamble,” said El Sahly, who… member of the committee who advised on the FDA’s final vaccine formulation. “Even if you have a high transmission beforehand, that doesn’t guarantee that the strain selection will be perfect.” In general, the effectiveness of a flu shot against illness is best when: about 60 percent. But like most other immunizations, the vaccine is great at curbing the seriousness from symptoms and keeping people away from the hospital; even a slightly mismatched vaccine could have a huge dent in the viruses’ impact. “Whatever happens will at least protect you a little,” Chu said.
Flu shots are also good at hedging bets. The standard “quadrivalentformulation contains safe, inactivated representatives of four branches on the flu tree: H1N1 and H3N2, subtypes belonging to the influenza A family, and B/Victoria and B/Yamagata, genera in the influenza B family. Flu A viruses generally change shape faster than their B-list cousins, so those ingredients change more often. The recording I got this weekend contained two updates, compared to last year’s recipe, that will hopefully prepare me better for the flu strains du jour. (Kalu pointed out another perk: We’re still waiting for the official green light for the COVID-19 vaccines for the under-12s, but the flu shot is now available for children from six months old.)
Regardless of how the flu hits us this winter, my recent vaccine is an insurance policy: Either way, I’m better protected than I was. Taking the picture was easy too. I was able to make an appointment on my first attempt; the injection itself, which was free and painless, only took a second at my local CVS. (Flu and COVID-19 shots can also be administered at the the same time.) It was clearly the awakening my body needed: within hours my arm was a little swollen; eventually the lymph nodes next door did, probably as they filled with hordes of grumpy, flu-prone immune cells, some of which probably emerged from a two-year sleep. I felt a little sore, a little tired. I felt so much better than before.