Health officials are identifying people who were exposed, including those on specific flights.
In November, Cameroon said it would receive 331,200 doses of the RTS,S vaccine, which is produced by GSK.
The latest suspected cases stem from exposures at a daycare provider.
Philadelphia health officials are tracking 4 confirmed measles cases, plus 2 suspected infections.
Low-income countries were hit hardest by coverage gaps and deaths from the virus.
The number of zero-dose children (14.3 million) decreased 21%, from 18.1 million in 2021, but was still 11% higher than the 12.9 million in 2019.
In one of the cases, the patient was unvaccinated and had traveled internationally.
Since the middle of May, 1,200 child deaths from measles and malnutrition have been reported from war-torn Sudan.
Increases in countries that already had good momentum overshadowed struggles other countries had with regaining lost ground.
The WHO reports 316 new mpox cases and 2 new deaths, and the UK warns about a rise in measles transmission.