The flu season is underway and people may be congratulating themselves for getting a flu shot, lamenting for forgetting or, in some cases, wondering why they even bothered to get stuck. In recent years, flu vaccines have not always lived up to their billing and some experts are pointing to a fragile culprit: Eggs.

Since flu shots were first created, the viruses for the vaccines have been grown inside of hen eggs. While using viruses that are grown this way is an inexpensive and widely popular method, it does come with drawbacks. According to a study published in the Proceedings of the National Academy of Sciences, viruses that are not grown in eggs may have a better chance of protecting people from the flu.

When viruses are grown in eggs, they naturally have to adapt. Sometimes, these adaptations are minor and don’t have a big impact on the effectiveness of the vaccine. But other times, the mutations can cause the vaccine to be less effective in protecting against the flu, which then causes more outbreaks.

An egg mutation that occurred last year caused the H3N2 flu shot to be substantially less effective. A certain component of the flu shot was mutated, and it could not target that component of the flu virus. Scientists already are concerned about a repeat this year.

Two flu vaccines created outside of eggs are already on the market. So far, the jury is still out on whether these alternatives are any more effective and work continues to perfect the processes.

Meanwhile, the sniffly, achy, tired public — as well as major drug manufacturers — are impatiently waiting for a vaccine that can put up a more reliable fight against the flu.