Prime Minister Boris Johnson is aiming to offer all UK adults a first dose by autumn.
But WHO spokeswoman Margaret Harris said it is morally and economically "the right thing to do" for the UK to help efforts elsewhere after vaccinating its top priority groups.
The UK has one of the highest levels of vaccine coverage, along with Israel and the UAE, but many poorer countries have not yet started immunisations.
An expert from the government's Scientific Advisory Group for Emergencies (SAGE) also warned leaving the virus unchecked in parts of the world will lead to more variants emerging.
When asked to clarify whether, once the UK has vaccinated its top nine priority groups, it should help other countries instead of continuing with the rest of the population, Ms Harris told BBC Breakfast on Saturday: “We’re asking all countries in those circumstances to do that: ‘hang on, wait for those other groups’.
“We’ll also appeal to all the people of the UK – you can wait.
“We’re asking countries, once you’ve got those (high risk and health care worker) groups, please ensure that the supply you’ve got access to is provided for others,” she added.
“While that is morally clearly the right thing to do, it’s also economically the right thing to do.
“There have been a number of very interesting analyses showing that just vaccinating your own country and then sitting there and saying ‘we’re fine’ will not work economically.
“That phrase ‘no man is an island’ applies economically as well.
“We in the world, we’re so connected and unless we get all societies working effectively once again, every society will be financially effected.”
Ms Harris said countries should be aiming for “two billion doses” to be “fairly distributed” around the world by the end of 2021.
The WHO's comments come as the European Union (EU) faces a vaccine shortfall. The EU is currently in a row with vaccine developer AstraZeneca after the pharmaceutical giant said it would not be able to meet its supply targets for the first three months of 2021.
The EU has also backed down on plans to block its vaccine exports to Northern Ireland, by triggering Article 16 of Brexit's Northern Ireland protocol.
Sir Jeremy Farrar, a SAGE member, warned that vaccinating “a lot of people in a few countries, leaving the virus unchecked in large parts of the world, will lead to more variants emerging”.
He said countries with vaccine supply deals could donate a proportion of doses to the WHO’s Covax global vaccine-sharing fund.
WHO director general Dr Tedros Adhanom Ghebreyesus has said a “me first” approach would prolong the pandemic.
WHO directors have previously said vaccine nationalism could cost high-income countries 4.5 trillion US dollars. This is almost half of an estimated 9.2 trillion dollar hit to the global economy, according to a report commissioned by the International Chamber of Commerce Research Foundation.
Earlier this month, it was revealed the UK has helped raise more than £730 million for the Covax Advance Market Commitment, including £548 million in UK aid to help distribute 1.3 billion doses of coronavirus vaccines to 92 developing countries this year.