Yep, this is an astronaut (Scott Kelly) giving himself a flu shot. Photo by NASA via Getty Images.
The protection you get from a flu shot wanes over time, leading to rumours that we should all be asking for a second flu shot in the spring. Not so fast! The current recommendation - to get a single flu shot, ideally during Autumn - is still your best bet.
"From what we know about the relatively short-lived boost in antibodies that our current influenza vaccines provide, I think it's realistic to believe that this waning by the end of the season is happening," says Richard Webby, a researcher at St. Jude who is also one of the people who decides which flu vaccines will be used each year. But that doesn't mean you need to double up on shots.
(Young children do need two shots, but only the first time they're vaccinated for the flu. And they should get both shots before flu season starts. On the other end of the spectrum, people over 65 can make up for their slightly weaker immune systems by getting a single high dose vaccine instead of the regular kind.)
You're still best off getting a single flu shot in April, to make sure that it fully takes effect before flu starts circulating in your area. If you wait any longer, though, you're taking a gamble. Webby points out that the better bet is to get the shot early and take your chances on the tail end of the season. If instead you delay the shot in autumn, you're missing out on early season protection for no good reason.
So what about a second flu shot in the spring? Unfortunately, there's no evidence that would help. There's also a possibility that a booster shot would leave you slightly less protected. "There is some suggestion that too frequent flu vaccinations may actually reduce the effectiveness of the vaccine, or even reduce the response you would get to another subsequent dose," Webby says. "While the jury is still out on this point, to me the potential down side of end-of-season vaccination outweigh any benefit."
So if you want to boost your immunity against the flu when you've already had your flu shot, you'll have to do it in more traditional, boring ways - like getting plenty of sleep and washing your hands.