The coronavirus and flu vaccines are safe for people to get at the same time, research suggests.
A UK clinical trial found that reported side effects were mainly mild to moderate.
There were also no negative impacts on the immune response produced by either vaccine when both were given on the same day, in opposite arms.
The Combining Influenza and COVID-19 Vaccination (ComFluCov) study looked at whether it was safe to give both jabs together.
Researchers say the results reinforce current coronavirus booster vaccine guidance, which is for both jabs to be given together where it is practically possible.
Dr Rajeka Lazarus is consultant in infectious diseases and microbiology at University Hospitals Bristol and Weston NHS Foundation Trust (UHBW) and chief investigator for the ComFluCov study.
"By conducting this study we have been able to establish that it is possible to protect people from both COVID-19 and flu at the same appointment," she said.
"This is a really positive step which could mean fewer appointments for those who require both vaccines, reducing the burden on those who have underlying health conditions and would usually be offered the influenza vaccine."
Two COVID and three flu vaccines were tested, meaning six combinations in all.
Study participants were over the age of 18 and had already received one dose of either the Pfizer-BioNTech or the Oxford-AstraZeneca jab, and were awaiting their second dose.
A total of 679 volunteers took part in the study across England and Wales.
They were randomly allocated to either receive their second dose of the COVID-19 vaccine and the flu vaccine at their first study visit, then a placebo at their second visit.
A second group received their second dose of the COVID-19 vaccine and a placebo at their first visit and then the flu vaccine at their second visit.
The most common side effects were pain around the injection site and fatigue.
The study was led by researchers at the Bristol Trials Centre, UHBW, and supported by the Clinical Research Network West of England.
The results are due to be published in The Lancet.
The data has been released as a preprint, and has not yet been through peer review.