Measles has killed 12 children in and around the western Indian city of Mumbai, authorities say.
The first death was reported around October 26 and 27, when three children died within 48 hours.
The city had 233 confirmed cases this year as of Wednesday, triple the 92 cases and two deaths reported last year.
Officials say a sluggish vaccination campaign amid the covid pandemic has contributed to the rise in infections.
The last reported death, on Tuesday, was that of an eight-month-old baby who was partially immunized, the local municipal body registered in a press release.
Measles is highly contagious – even more so than Covid – and can cause serious complications, especially in children under five.
The disease, which causes coughing, rashes, and fever, can be prevented with two doses of the mumps, measles, and rubella (MMR) vaccine.
There have been several large outbreaks in countries in Europe where the uptake of the MMR vaccine has been low.
Nine out of 10 people can get it if they are not vaccinated and exposed
In addition to causing a distinctive rash, measles can lead to serious complications, including pneumonia and brain swelling, and can sometimes be fatal.
Vaccination can eliminate almost all of these risks.
Two doses of the MMR vaccine provide 99% protection against measles and rubella and 88% protection against mumps.
When a high percentage of the population is protected through vaccination, it becomes more difficult for the disease to spread from person to person.
But since the start of the Covid pandemic, there has been a worrying decline in the number of children receiving these vaccines on time.
In 2020, 23 million children did not receive all essential childhood vaccinations. That is the highest number seen since 2009 and 3.7 million more than in 2019, according to Unicef.
Mumbai authorities say around 20,000 children did not receive the measles vaccine on time due to the pandemic.
“Now, we are tracing all these children and organizing vaccination camps as a priority,” Dr Mangala Gomare, Mumbai’s chief health officer, told The Indian Express newspaper.
Health officials say other problems, such as vaccine questions, hamper the campaign.
“After vaccination, some children develop mild fever and pain in the injected area, so parents don’t let them get vaccinated,” Shreya Salvi, a health volunteer, told the newspaper.