Lifelong Protection in Most Cases
The MMR vaccine, typically given as two doses in childhood, offers 93% and then 97% protection against the highly contagious virus. During the 2022-to-2023 school year, the measles vaccination rate among kindergarten children nationwide was 92%. That sounds like a high rate, Dr. Lim said, “but because measles is so contagious, vaccination rates need to be 95% or higher to contain transmission.”
One person with measles can infect anywhere from 12 to 18 other people, she said. When an infected person coughs or sneezes, tiny droplets spread through the air. “And if someone is unvaccinated and exposed, 9 times out of 10, that person will go on to develop the disease.” She said given the high transmission rate, measles often spreads within families to infect multiple children.
If you know you’re not vaccinated but exposed, the advice is to get the measles shot as quickly as possible. “There is a recommendation to receive the MMR vaccine within 72 hours as post-exposure prophylaxis,” Dr. Lim said. “That’s a tight time window, but if you can do that, it reduces the risk of developing measles significantly.”
If you’re unsure or do not remember getting vaccinated against measles as a young child, your health care provider may be able to search state registries for an answer. If that doesn’t work, getting revaccinated with the MMR vaccine as an adult is an option. “There is no shame in getting caught up now,” Dr. Barocas said.
Dr. Lim agreed. “There is really no downside to getting additional doses.”
A version of this article appeared on WebMD.com.