UK health officials are putting a temporary limit on who can have a hepatitis B vaccination because stocks are running low.
The move is in response to the wider, global shortage of the jab caused by manufacturing issues.
UK travellers are being told they may not be able to get it before they leave Britain for higher-risk countries.
Babies and high-risk groups will be prioritised under the measures that are expected to continue into 2018.
A spokeswoman for Public Health England said: “All those who need to have a hepatitis B vaccine will be offered it in due course.”
But she said some people wanting to be vaccinated now may not be able to have the jab.