MANILA — The Philippines expanded the area of a declared measles outbreak on Thursday from the highly populated capital to nearby regions, after a steady rise in infections and deaths attributed to the disease in recent weeks.

The government’s Epidemiology Bureau raised the “red flag” after an increase in infections in the capital, Manila, as well as the northern and southern ends of Luzon, the island that includes the capital.

The Department of Health said that measles had killed 55 children age 4 or younger at San Lazaro Hospital in Manila since the start of the year.

According to the Epidemiology Bureau, there were 196 cases of measles in metropolitan Manila from Jan. 1 to 19, compared with 20 in the same period last year. The region had 10 times more measles cases in 2018 than the year before.

“We are expanding the outbreak from metro Manila to the other regions as cases have increased in the past weeks and to strengthen surveillance of new cases, and alert mothers and caregivers to be more vigilant,” Health Secretary Francisco Duque said.

He said the outbreak had first been declared only in metropolitan Manila, a megacity of some 12 million people packed in sprawling suburbs and slums, but that further monitoring suggested infections had spread to other areas.

Dr. Duque urged people to participate in a government-sponsored measles vaccination program, emphasizing that the injections had been “proven effective and safe.”

Trust in immunization programs in the Philippines was seriously damaged in 2017 after the French pharmaceutical giant Sanofi Pasteur admitted that a dengue vaccine it had distributed in the country, Dengvaxia, could backfire: If people who never had dengue were vaccinated and later become infected, the vaccine could provoke a much more severe form of the illness.

The government responded angrily, stopping the Dengvaxia program and asking Sanofi Pasteur to reimburse the 3.5 billion Philippine pesos, or about $67 million, it had spent on the vaccine. State prosecutors have recommended that charges be filed against Dr. Duque and Benigno S. Aquino III, the president at the time; two congressional committees also recommended charges this week.

But another consequence of the immunization scare is that many parents stopped vaccinating their children against other diseases, health officials said.

Government officials have given diverging accounts of the effects of the Dengvaxia program. Persida Acosta, the government’s public attorney, blamed the vaccine for the deaths of 14 children, though an expert panel concluded otherwise. Ms. Acosta has accused the Health Department of paying families to drop their criminal complaints, which Dr. Duque called “baseless” last month.

In December, a group called Doctors for Truth and Welfare, led by a former health minister, criticized Ms. Acosta and another official in the Public Attorney’s Office over their comments on Dengvaxia.

“We call for a halt to the continuous spread of unproven claims of deaths caused by the dengue vaccine by the same unqualified but noisy people who are largely responsible for the fall in vaccine confidence in the country,” the group said.

On Thursday, Justice Secretary Menardo Guevarra said that Ms. Acosta was “just doing her job” and did not mean to scare the public into avoiding vaccinations.

Salvador Panelo, a spokesman for President Rodrigo Duterte, said on Thursday that the immunization rate for measles was low because the Dengvaxia scare had undermined public confidence in the government’s vaccination program.

“Even if you go house to house,” Mr. Panelo said, “if they believe that their children could die due to immunization, why would they have them immunized?”