British researchers have identified genetic factors that may explain why some people have adverse reactions to vaccines.

The findings, published in the journal Nature Immunology, indicate a pattern in gene-expression immune cells may cause some people to have flu-like symptoms or other minor reactions to shots, Medical Xpress reports.

That, in turn, could help doctors predict which people are likely to have adverse responses to vaccinations.

Although no evidence has been found linking vaccinations as a cause for autism spectrum disorder, other less well-known adverse reactions — such as flu-like symptoms after receiving a flu shot — are not uncommon.

To find out why some people experience such reactions, the researchers tracked 178 healthy adults who received flu vaccinations and identified several gene-expression immune cells that were responsible for adverse reactions.

About 20 percent of those vaccinated experienced an adverse response to some degree.