Shikha Garg, MD, MPH: Age's Role in Flu Hospitalization

The CDC Influenza Division medical director reported new findings at IDWeek showing older patients with influenza subtype A were more likely to be hospitalized.

Shikha Garg, MD, MPH

A new study presented at the IDWeek 2019 Annual Meeting in Washington, DC, last week showed variations in influenza (flu) hospitalization among patients of different age and flu subtype.

The findings, which used national data from the most recent flu season, provides clinicians a clearer perspective on what particular influenza A subtypes affect which patients more aggressively—vaccination or not. But more than anything, it emphasizes the potential value of an annual flu vaccination.

In an interview with MD Magazine®, study author Shikha Garg, MD, MPH, medical officer of the Influenza Division at the US Centers for Disease Control and Prevention (CDC), detailed the study results and what they mean for flu protection.

MD Mag: Can you speak a little bit about the impetus for this study?

Garg: So what we wanted to do was, we really wanted to increase the evidence base for the benefits of influenza vaccination. Every year, millions of people get influenza, hundreds of thousands of people get hospitalized with influenza, and tens of thousands of people die from influenza.

So what we really wanted to do was show the benefits of vaccination in preventing some of these severe outcomes.

MD Mag: Could you summarize the findings?

Garg: We used the Influenza Hospitalizations Surveillance Network, or FluServ-NET, to look at data from over 40,000 adults who were hospitalized with influenza over 5 seasons, across over 250 acute care hospitals, in 13 states. And what we did was look at severe outcomes in these people including death, ICU admission, mechanical ventilation, and pneumonia, and adults who had received the flu vaccine versus those who hadn't received the flu vaccine prior to their hospitalization.

So what we found was that in adults 18-64 years of age, influenza vaccine reduced the odds of death by 36%, mechanical ventilation by 34%, ICU admission by 19%, and ammonia by 17%.

And then in adults 65 years older, flu vaccine was associated in those with A(H1N1) with reduced odds of mechanical ventilation by almost one-half, and ICU admission by almost a third. And in that group, it also shortened the hospital length of stay.

So overall, we saw that flu vaccination, although it's not always perfect—it's variable in how it works, and that some people who get vaccinated can still get sick—flu vaccine really did reduce the risk of severe outcomes.

MD Mag: What are you hoping clinicians to take away from this research?

Garg: I hope that they can take away the message that there's a lot of different benefits of flu vaccine. So again, I think, flu vaccine effectiveness can vary from year to year. But I think this study really shows that even if people get sick, despite getting vaccinated, that they can really have some substantial benefits of flu vaccine.

So it's really important to vaccinate all people 6 months and older every year. And I'll also add that all of the 3 different flu vaccine viruses—A(H1N1), A(H3N2), and B—circulate every year. And so, the study shows that you get protection against the influenza A(H1N1) virus, but all viruses circulate every year.

MD Mag: Anything else you'd like to add?

Garg: It's flu season now, and it's really important for everyone to get vaccinated—and preferably, preferably by the end of October.