Health officials have warned that action is needed to prevent a rubella outbreak, which can be particularly dangerous to pregnant women.
Public Health Wales and national deaf-blind charity Sense say about 38,000 young people in Wales have not had the measles mumps and rubella (MMR) jab.
They welcomed the efforts to increase vaccinations in light of the measles epidemic centred on Swansea.
But they said more people need to have the recommended two doses.
The measles epidemic has seen 1,094 cases reported in the Swansea area, with 1,257 across Wales.
If rubella is contracted by a pregnant woman, it can cause babies to be born with combined sight and hearing loss along with life-threatening heart conditions and a long list of other health issues.
Joff McGill, of Sense, said: “We can’t sit around and wait for rubella outbreaks to follow measles – now is the time to catch up and stay ahead of rubella.
“We must act now to protect pregnant women and their unborn babies. Women who are unsure of their vaccination history and are thinking about becoming pregnant should contact their GP for advice.”
Mr McGill added: “The large group of 38,000 unvaccinated young people in Wales, along with evidence of increasing susceptibility to rubella in younger woman and in women from ethnic minorities, means immunisation can no longer be a childhood issue.
He said the single measles vaccination did not protect against rubella and a programme of single vaccines would mean more people unprotected for longer.
“MMR is the only effective way to prevent the spread of the disease and the associated risks.”
Dr Marion Lyons, director of health protection for Public Health Wales, added: “We have been warning for some weeks now of the risk of measles to those not vaccinated with two doses of MMR, but it should be remembered that the vaccine also protects against mumps and rubella.
“At present we have not seen cases of rubella in Wales for several years, but the disease is not eradicated and there is every possibility of rubella outbreaks in the future.
“It would be a huge shame to see this disease re-emerging in Wales and affecting pregnant women and their babies.”