Passenger need show the driver a text or email on their phone, or a letter or other printed document which confirms an appointment for that day.
The free travel offer is in place until further notice.
County Coun Charlie Edwards, cabinet member for highways and transport, said: “We want to make it as easy as possible for people in Lancashire – particularly in some of our more rural areas – to get to the vaccinations sites.
“We recognise that not everyone has their own transport, but it’s vital that everyone has equal opportunity to get vaccinated against Covid-19.
“This is a great initiative, and we hope it will help encourage as many people as possible to get vaccinated – whether that’s a booster or first or second jab.
“Lastly, I would like to say a huge thank you to all the bus operators taking part in this scheme.
“We know operators have their own challenges to deal with, so their support in this national effort is massively appreciated.”
Dr Sakthi Karunanithi, director of public health for Lancashire County Council, said: “Lancashire is aiming to deliver around 500,000 jabs in the next three weeks – a doubling of the current vaccination rate.
“The NHS is leading the booster vaccination programme and have asked for support from local authorities and other Lancashire partners.
“It’s absolutely vital that we get as many people as possible boosted because we know that against Omicron, two doses does not provide sufficient protection.
“It is also important that we provide easy access to anyone who may not have yet come forward for their first or second jab.
“We know transport could be a barrier so we hope this offer will enable more of our residents to get their life-saving jabs and build up our vaccine defences.
“I would also like to thank our local bus operators for their support in this initiative.”