Researchers discover how simply flu viruses can survive around yearly vaccinations, giving them insight on how to make more effective yearly flu shots.

Outside a few Southern states, seasonal flu activity remains low, but experts at the U.S. Centers for Disease Control (CDC) expect activity to start ramping up in the next few weeks.

While the CDC recommends vaccinations for all eligible people, the vaccines currently in use won’t be as effective next year—because the viruses are always evolving.

The flu vaccine works by using inactivated parts of three major flu viruses (the three that research shows will be most common in the upcoming season), so the body can build antibodies to defend against those viruses. But that continual evolution means the antibodies won’t recognize some new viruses.

Recently, a research team in the Netherlands discovered how the virus evolves. And as with all battles, knowing the enemy’s weakness is a valuable strength.

Feeling Funny? Check Yourself for Six Symptoms of the Flu »

Led by Derek Smith, a professor at the University of Cambridge, and Ron Fouchier, a professor at Erasmus Medical Center in The Netherlands, a research team has discovered that flu viruses escape immunity from vaccines by simply subbing out a single amino acid.

The discovery, as well as finding that these changes occur in only seven places on the virus’s surface, and not the 130 places previously believed, may help create more effective vaccines in the future. The team’s findings were published in the latest issue of the journal Science.

According to the researchers, these single changes were responsible for the majority of flu virus evolution since at least 1968.

In their labs, the research team created viruses with varying combinations of amino acids and found that changing one of these acids allowed the viruses to escape immunity. Previously, researchers believed that a number of other changes were needed to outsmart a vaccination.

“This work is a major step forward in our understanding of the evolution of flu viruses and could possibly enable us to predict that evolution,” Smith said in a press release. “If we can do that, then we can make flu vaccines that would be even more effective than the current vaccine.”

Learn the 6 Possible Side Effects of the Flu Shot »

Just as viruses can evolve around vaccinations, bacteria can evolve around antibiotics, leaving our best medications useless against certain strains.

The CDC says that the majority of chest infections related to the common cold are related to viruses, which are not affected by antibiotics. As many as 10 million children each year are at risk of complications caused by unnecessary antibiotic prescriptions.

While the rate at which doctors are prescribing antibiotics is decreasing, last week the CDC released a set of new guidelines for giving children antibiotics for the common cold.

Besides fueling antibiotic resistance, the unnecessary use of antibiotics frequently causes side effects including nausea, diarrhea, vomiting, dizziness, and headache.

Read More: Why Antibiotics Shouldn’t Be Used for the Common Cold »