Targeting Predominant Strains of Influenza


Experts examine the yearly modifications in the formulations of flu vaccines and explore the variations in the adverse events experienced across different types of flu vaccines.

Rodney E. Rohde, PhD, MS, SM(ASCP)CM, SVCM, MBCM, FACSc: Dr McDonough, how does the composition of flu vaccines change annually? In other words, how do we forecast and select those predominant strains that we talked about to target for protection?

Randy McDonough, PharmD, MS, BCGP, BCPS, FAPhA: Adam touched upon this already. But it’s really interesting to me to watch the process because it never stops. It’s yearly and on a regular basis; you’ve got 144 national influenza centers in 114 countries. And they’re all looking to see what vaccines or what viruses are out there so they can pick the right ones. But there’s a lot of genetic characteristic testing that they’re doing, antigenic characteristic testing that they’re doing. They’re doing serum studies. So it’s not just the surveillance. It’s also the laboratory studies that they’re doing as well to really come up with the right strains we need protection against. It’s quite a process. And then it comes to each country to make that decision. Here in the United States, you’ve got the FDA…that will take all that information and say, “OK, these are the strains that we’re going to make sure we’re going to be protecting our patients against.”

Rodney E. Rohde, PhD, MS, SM(ASCP)CM, SVCM, MBCM, FACSc: It really is a fascinating conversation. Again, when I’m talking to the public about this as a virologist, as a medical laboratorian, not a pharmacist, but that inner mix of that information around that is talking about that with people. Because what I think people have to understand is that it’s not a straight fix annually, especially with influenza; we’re always going to see these changes, and the CDC [Centers for Disease Control and Prevention] and the WHO [World Health Organization], and even how that information percolates up from local hospital systems and into health departments to get those variables and variants, so that you get the right composition in those vaccines. It’s a big, complex process. I think generally people think it happens magically, but it’s very different every year.

Randy McDonough, PharmD, MS, BCGP, BCPS, FAPhA: I think it’s really important too from, again, a pharmacy perspective that we’re keeping up with the information, the literature, to make sure that it’s current so that when that flu season does hit,…you’re prepared to educate the public and make sure they fully understand.

Adam C. Welch, PharmD, MBA, FAPhA: [This is] especially [so] with the evolution of flu vaccines over the last decade. A decade ago, we were trying to identify the best 2 type A influenza strains to put in there and the best type B influenza strains. So there were 3 strains in total. We realized over the years that we were right about half the time with type B. So let’s put another B strain in. So now every flu vaccine on the market in this country is quadrivalent with 2 type A’s and 2 type B’s.

Rodney E. Rohde, PhD, MS, SM(ASCP)CM, SVCM, MBCM, FACSc: Yes, and I think a really important point to make is that type A is typically those pandemic strains but type B can also be very broadly regional. So now you have 4, basically; hence the name quadrivalent.

Adam C. Welch, PharmD, MBA, FAPhA: And we’re seeing that if what’s circulating across the country is predominantly H3N2, we’re going to see a lot more hospitalization rates than if it’s H1N1, for example.

Rodney E. Rohde, PhD, MS, SM(ASCP)CM, SVCM, MBCM, FACSc: I think it just speaks to the expertise and how we’ve drilled down now into those actual variants. Again, I think [this is] a product of COVID-19. I think the public also is now hearing that and wondering, well, what variant is it? This is interesting for me as an educator, because in the past that was a different conversation, and now people at least topically know that it’s a different virus.

Transcript edited for clarity.

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