"No strain, no gain" may be the mantra of fitness buffs (better than "no pain, no gain"), but when it comes to understanding what happens to the flu virus year to year, there's a lot of strain to gain solid data, even for researchers.

But you can relax. We’ve got you covered.

Fact 1: There are new mutant strains of the H1N1 flu virus emerging that allow the virus to dodge the antiviral medication oseltamivir (also known as Tamiflu).

Fact 2: Other antivirals remain effective against the new mutant flu viruses — just make sure if you get the flu, you're given one of the effective antivirals.

Fact 3: The really good news is that the flu vaccine still offers a lot of protection against viruses with these mutations, with few risks of serious negative side effects. Everyone 6 months and older qualifies for vaccination.

In March 2024, the Centers for Disease Control and Prevention recommended that 2024-2025 U.S. flu vaccines be three-component (trivalent), and the current four-component (quadrivalent) flu vaccines no longer need to be included in the formulation.

And there's another new flu shot on the horizon. Moderna is heading for phase 3 trials of a flu/COVID-19 combination vaccine. And recently, the Food and Drug Administration added a recommendation that the shots include the KP.2 strain of COVID-19, a descendant of the highly contagious JN.1 variant.