Fight The Flu
Fall is my favorite season. Since I was a kid, I’ve always loved the crisp air, warm colors, and earthy aromas of autumn. Maybe it’s also that my birthday is in October — or that I love the color orange. And candy corn. Who the hell knows.
Autumn beckons us to rake leaves and purchase oversized bags of Halloween candy at CVS.
It also signals the start of flu season.
So many of my patients are inquiring about the flu and how it relates to COVID-19, so today I present you with a Q & A all about the flu.
(If you’re not quite ready for flu fanfare, you can listen here to the COVID Q & A that I recorded last week on Instagram.)
Q: What exactly is the flu?
A: The “flu” is a respiratory illness caused by a virus called Influenza. Every year we get a few new strains in circulation. The influenza virus typically causes symptoms like cough, sore throat, fever, body aches, headache, and fatigue. It can cause pneumonia and other more severe symptoms. Flu can also be fatal.
Q: When does flu season officially start?
A: In the US, the annual flu season generally starts in October and lasts till early spring, with a big uptick in December, depending on geography.
Q: What about last year? Didn’t we see very little flu in the 2020-2021 season?
A: Yes. We saw very little flu last season, largely as a result of mitigation measures we used against COVID-19 (masks, distancing, ventilation) — plus the flu shot. Last year, 10% more adults got vaccinated, and sooner than in previous years.
Q: How many people die from the flu every year?
A: The CDC estimates that, depending on the season, approximately 12,000-60,000 people die from influenza every year in the U.S.
Q: What factors impact flu-related mortality from year to year?
A: Three major things affect how deadly the flu will be each year:
virulence of the dominant strain of the influenza virus
the effectiveness of the vaccine that year
the proportion of the population that actually takes the vaccine
Q: How effective is the flu shot?
A: The effectiveness of the flu vaccine varies from 20-60% depending on the year. But it’s important to know that even when vaccine effectiveness is low, it can have a major impact on morbidity and mortality. For example, despite a mere 29% effectiveness of the flu vaccine in the 2018-2019 flu season, the CDC estimates that the vaccine prevented 3500 deaths.
Q: Is it possible for people to get COVID and the flu together? And if so, how bad will that be?
A: Yes. Cases of co-infection in the US and overseas have been observed. While we don’t have enough data to know exactly if and how much sicker patients will get if infected with both viruses, it stands to reason that infection with flu and coronavirus together would lead to worse clinical outcomes than either alone.
Q: How will doctors be able to tell the difference between COVID-19 and the flu?
A: TESTING. Since both viruses present in similar ways (cough, fever, body aches, etc), diagnostic testing for both viruses is critical. As you know, we have rapid antigen (aka “infectiousness”) tests and PCR tests for COVID. For more discussion on COVID testing, see my recent newsletter here. To test for the flu, we currently only have PCR testing; rapid antigen testing or home testing for flu doesn’t yet exist.
Q: How important is getting a flu vaccine this year?
A: Very. Both coronavirus and flu cause significant morbidity and mortality. And outbreaks of both could quickly overwhelm healthcare systems. The vaccine is our most powerful tool against the flu. Every year our goal should be increased vaccine uptake, but this year it is especially critical to get your flu shot.
Q: Are flu and COVID-19 spread in the same or different ways?
A: Both viruses are predominantly spread person-to-person and in the air. Flu is thought to spread more by droplets (larger air-borne particles) and coronavirus by smaller particles called aerosols. Therefore some of the interventions we’ve employed to decrease the spread of COVID have also decreased the spread of flu.
Q: Does getting the flu in the past protect people from getting it again?
A: Getting sick and surviving the flu once won't necessarily prevent illness with another strain that is different enough from the one you had in the past. There is some cross-reacting protection, though. People who survived the 1918 flu, for example, still have active antibodies to that strain. Natural immunity to flu just isn’t as durable because influenza doesn’t stimulate the immune system (specifically the T cell response) that well—and certainly not as well as COVID itself and the COVID vaccines do to prevent reinfection or breakthroughs. Each flu shot does confer somewhat additive immunity, but because the strains vary year to year, we need to switch up the vaccine to stimulate production of the appropriate antibodies to fight that particular strain in circulation.
Q: Are the same people at highest risk for COVID-19 also at highest risk for flu?
A: Generally yes. Advanced age, underlying conditions like heart, lung, and kidney disease, immune deficiencies, and obesity, for example, put people at higher risk from both viruses. Kids ages 0-5 years old—especially those under 2 years—are at higher risk of developing serious flu-related complications. Respiratory infections in general can be particularly difficult for babies due to small airways.
Q: When should people get the flu shot?
A: The short answer is: whenever you can. The more sophisticated answer is this: ideally two weeks before the virus starts circulating in our communities (which is always a guess but can be as early as October). There is some evidence to suggest an approximate 10% drop in vaccine effectiveness for preventing hospitalizations in our highest-risk groups, so I generally recommend getting the flu shot in mid- to late October.
Q: Should I separate the flu shot from my COVID shot?
A: The CDC and AAP agree that you can get the flu and COVID shots the same day.
Q: Which flu shot should I get?
A: The standard flu shot is “quadrivalent,” meaning that it covers four strains of the flu and can be given to anyone ages 6 months and older.
The high-dose (HD) flu shot is four times the strength of the standard flu shot, is also quadrivalent, and is appropriate for patients age 65 and above, especially those with chronic disease.
Flublok is three times the strength of the regular flu shot, is quadrivalent, and can be given to any patients ages 18 and up who are immunocompromised or need additional protection. It can also be considered for patients 65 and older who had moderate-severe reaction to HD flu.
Q: Should I get two flu shots this year, one in fall and one in early 2022 as a booster?
A: Currently there is no recommendation from the CDC or other expert group on giving two flu vaccines this year, but this can be an individual discussion with your doctor. For now, the main focus should be getting one dose this fall.
Q: Are there medicines available to treat the flu? And is it treated differently than COVID-19?
A: Oseltamivir (aka “Tamiflu”) and the newer Baloxavir (aka “Xofluza”) are prescription antiviral medications that target influenza. They work by halting replication of the virus and work best when started early on in the course of infection. Sadly, these medications have no effect against coronavirus. Targeted oral antiviral medications to prevent non-hospitalized COVID patients with mild to moderate symptoms from getting sicker are happily in the pipeline. (But still the best way to prevent COVID is to get vaccinated!)
Q: Do I still need a flu shot if I a) “never” get sick or b) “only got the flu when I got the flu shot”?
A: Yes! Similar to the COVID vaccines, the flu shot not only protects you; it protects others as well. The flu shot cannot cause the flu; it can cause transient flu-like symptoms (muscle aches, low-grade fever) that signal your body getting ready for the real thing. I promise you: the flu is a whole lot worse than the potential side effects from the flu shot!
Q: But why should I get the vaccine if it’s only 20-60% effective?
A: Because even if not 100% effective, the flu shot will blunt the effects of the virus, reduce your likelihood of infecting others, and save lives.
Q: But, but, but….I don’t like shots. Waaaah!!
A: Other than last flu season, every fall and winter I treat many unvaccinated patients for the flu. Vaccination is important for kids, too: 80% of the children who died of influenza were unvaccinated. I can’t think of a single flu patient who — without my prompting — hasn’t vowed to forever get the flu shot going forward! Flu is a nasty bug and can take you down for a week or two. The vaccine is our best weapon against it. It’s also something we can actually control in these uncertain times.
I will check in next week. Until then, be well.