Shaun Grannis, M.D., M.S., discusses findings from a recent CDC study that illustrate why vaccines are highly effective in elderly populations.
There are many factors that influence the number needed to vaccinate. So the susceptibility of an individual to disease is a factor. So what we found in this paper as well was that the older an individual is, the more medical issues that they have, the frailer that they are, the number needed to vaccinate decreases, meaning that you need to vaccinate fewer older people to prevent older individuals from being hospitalized. What that means is vaccines among the elderly are highly effective at preventing those most severe outcomes and death.
Dr. Grannis discusses how health-seeking behavior can skew the number needed to vaccinate.
The number needed to vaccinate for emergency department visits showed a different pattern. It actually showed it was more effective at preventing emergency department visits among younger people than older people. You say, why wait a minute. You told me that as you get older, it’s better. Well, that has to do very likely with health-seeking behavior. A lot of people, particularly younger people who don’t have Medicaid or Medicare, use the emergency department as a primary care provider. Older people go see their doctor. They don’t, you know, just willy-nilly show up at the emergency department. So what we saw was that the vaccine kept younger people out of the emergency departments more than it did the older people. So health-seeking behavior, kind of skewed number needed to vaccinate there and that’s a good textbook example of how different factors can impact number needed to vaccinate.