US Families Opt for Earlier Second Measles Shots as Cases Surge

Measles cases are accelerating in the United States, with twice as many confirmed cases as last year. In this situation, more parents are opting for earlier vaccination, especially the second dose of the measles, mumps and rubella (MMR) vaccine, which can be given as soon as four weeks after the first.

Giving the second shot soon after the first aligns with guidance in countries such as Germany, the United Kingdom and France. The US Centers for Disease Control and Prevention (CDC) also says it is an option.

Elias Kass, a naturopathic physician and vaccine advocate in Seattle, Washington, said more parents have heard about doing it 'early'. The CDC typically recommends the first MMR shot after age one and the second between the ages of four and six. But when measles cases began increasing a few years ago, Kass began recommending the MMRV shot, which combines the second MMR and chickenpox vaccines into one, at 15 months of age.

Kass said more parents are taking that recommendation now, and their thinking is straightforward: 'There's no reason to wait, measles is here now.'

Margot Taylor, a mother in Chicago, has three young children with three different MMR vaccination histories. Taylor said: 'All three of them are fully vaccinated, but it's had to be accelerated because of all of these increasing cases. We've gone backwards so much.'

Her oldest, born in 2019, received her shots at ages one and four. Taylor said measles 'wasn't on my radar' at the time. But with her second child, born in 2023, she was surprised when the paediatrician recommended the second shot at age two; Chicago was battling a measles outbreak, so they went ahead with it.

Her third child, born in 2025, received the first shot after her first birthday, and the second shot only three months later, in June.

Taylor worried the shots might not work as well if given so early. But evidence shows the vaccines still work well at earlier ages; the recommendation to give the second dose between four and six is based more on logistical concerns, to ensure children have both shots before kindergarten and to cut down on doctors' visits, because other shots are also typically given at those ages.

Taylor knows how vital the MMR vaccines are. When her third daughter was too young for the first dose, she was exposed to measles at an airport during the west Texas outbreak. When the baby, only a month old, developed a fever afterwards, they rushed to hospital and stayed in a negative-pressure room until the test came back negative for measles.

Germany had similar recommendations to the US until 2001, when an outbreak brought a wave of illness and death that led the country to recommend the first shot at 11 to 14 months and the second at 18 to 23 months. In 2020, they moved the second dose to four weeks after the first.

Catherina Becker, a scientist in Germany, said there is absolutely no indication so far that any child vaccinated twice in any rhythm would have a higher risk of measles than someone vaccinated under the old rule. The CDC should 'absolutely' consider a stronger recommendation to give the second shot earlier, she said. Her own son was two and a half when he got his second measles vaccine, delayed only because he was recovering from chickenpox.

Some parents are also choosing to get their babies the first shot at the age of six months, which the CDC recommends in areas with outbreaks, before international travel, and after exposure to measles. Those infants should also receive a third dose.

If a mother was vaccinated against measles before a pregnancy, that immunity is shared in utero, so the baby is protected for the first few months of life. That is why a third dose is recommended if infants receive the first dose early, because the baby may still have some maternal antibodies and thus may not establish a strong response to a vaccine at six months.

The second MMR shot is different from other boosters. Most people mount a strong response to the first shot, which is why only one shot was recommended until 1989. Scientists then discovered that some people do not respond to the first shot and need a second. That is also why people born before 1989 may need a second shot now. In Kass's words, 'It's a second chance to respond for the first time.'

Becker looks to past outbreaks to understand the effectiveness of the shots. In a 1998 outbreak in Alaska, only 17 people were sickened at a school where nearly all students, some 2,186 in total, had received measles shots. She compared it with a 2010 outbreak at a Waldorf school in Germany where nearly half of the 300 students were unvaccinated and 71 people were sickened. 'It shows you what the measles vaccine does for you, it protects you from getting this thing,' she said.