According to findings by Michigan State University, the preservative Teri-butlhydroquinone or tBHQ - a common additive used in cooking oils - has been linked to hindering influenza vaccines.
"If you get a vaccine, but part of the immune system doesn't learn to recognise and fight off virus-infected cells, then this can cause the vaccine to be less effective," says Robert Freeborn, who co-led the study.
Speaking to News Corp, professor Robert Booy, Head of the Clinical Research team at Australia's National Centre for Immunisation Research and Surveillance, described the study as a tease.
"It's not yet been tested on humans but in further research, I would be very keen to see if our favourite fish and chips is actually helping to make us sick."
If you're concerned about your immune system, here are some great ways to fight colds off faster.