Formulating the 2021-2022 Flu Vaccine


Slight variation in the flu vaccine from last season based on limited data.


Peter Salgo, MD: Now we come back to those poor flu vaccine developers. Here they are, without a lot of data from the previous flu season. How are they going to know which strains to target, making the vaccine for next year?

Jason Gallagher, PharmD: It’s an interesting question.

Peter Salgo, MD: Thank you very much.

Jason Gallagher, PharmD: They’re following the same recipe they always do, which is what the WHO [World Health Organization] says months in advance. It’s already been decided what the formula is going to be. In the quadrivalent vaccines, there are always 2 A strains and 2 B strains. The 2 B strains have been consistent for several years now, but the low levels of circulating virus aren’t 0, so they still have made a determination based upon what those circulating strains have been. Who knows? It’s sadly an open question as to how good that vaccine is going to be this upcoming year, as it truthfully always is. This is just a year with even more uncertainty.

Peter Salgo, MD: Just when you thought it was safe to go back in the water. Bill?

William Schaffner, MD: To expand on what Jason said, WHO has a surveillance network that’s genuinely global. People are interested in flu, so they’re monitoring respiratory illnesses around the world, literally 24/7. Our technology today can get us to influenza viral subtypes very quickly. Our surveillance is much more sophisticated. We have not yet seen a new variant of the influenza virus show up anywhere. The current quadrivalent vaccines—they’re all quadrivalent this year, thank goodness—will represent the dominant strains that have been circulating for at least the past 2 years.

Peter Salgo, MD: My understanding of flu vaccines is that they were formulated yearly based on the flu that was already in Asia and heading this way, because that’s how it appears to propagate. What you’re telling me is that there was so little flu that maybe the vaccine is the same as last year? Is that what you’re saying?

William Schaffner, MD: Only slightly modified. Right, Jason?

Jason Gallagher, PharmD: Yes. It’s similar. It’s always a crapshoot. This year there’s just less odds to bet on.

Peter Salgo, MD: If you look at the biology that we were discussing, if there’s less flu being transmitted person to person and fewer generations of flu, then the modification rate on the virus itself is probably lower. Maybe it hasn’t morphed as much as we think or feared. Maybe these vaccines are going to be effective for the basic biological reason that it hasn’t mutated very much. What do you think, George?

George Loukatos, MD: Either way, the bigger challenge to me, as a clinician, is figuring out who’s going to take the flu vaccine, who’s going to take the COVID-19 vaccine, how this is going to affect us getting these vaccines into people, and what has taken place over the last year to affect that behavior. It’s a double-edged sword. In general, people have done a lot more research and are educating themselves about vaccines. To that end, will they be more likely to take a flu vaccine? Or are they going to say, “The flu vaccine is only 50% effective, whereas the COVID-19 vaccine is 90% effective, so why bother taking it?”

The populace is getting more educated on the vaccines themselves. As a clinician, my biggest challenge has always been trying to get the science into people’s heads rather than, “I got a flu vaccine and I got the flu.” We’ve all heard that a thousand times, and that’s what we’re combating. How is this going to translate into getting the vaccine into people and how will that affect the season?

Peter Salgo, MD: There is that whole question of, “I got the flu vaccine, but I got the flu.” What’s been pounded about COVID-19 is you that got the flu, but consider how bad it could have been if you hadn’t been vaccinated. People have heard that regarding COVID-19. Some have listened, some haven’t.

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Transcript edited for clarity.

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