2019年4月29日，在犹他州普罗沃的犹他县卫生部门，一名护士正在为一名儿童的手臂做准备，以接种默克公司生产的麻疹、腮腺炎和风疹病毒疫苗。
A nurse prepares a child’s arm to receive a measles, mumps and rubella virus vaccine made by Merck at the Utah County Health Department on April 29, 2019 in Provo, Utah.
家长们正选择更早接种第二剂MMR疫苗，这与德国、英国和法国的指导方针一致。美国的麻疹病例正在加速增加，确诊病例数是去年的两倍，越来越多的家长选择更早接种疫苗——尤其是麻疹、腮腺炎和风疹（MMR）疫苗的第二剂，该剂可在第一剂接种后最快四周时接种。
Parents are opting for a second shot of MMR vaccine sooner, which aligns with guidance in Germany, the UK and France Measles cases are accelerating in the US, with twice as many confirmed cases as last year, and more parents are opting for earlier vaccination – especially with 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 what some other countries, such as Germany, the United Kingdom and France, recommend – and the US Centers for Disease Control and Prevention (CDC) also says it’s an option.
在第一剂之后不久接种第二剂，与德国、英国和法国等其他一些国家的建议一致——美国疾病控制与预防中心（CDC）也表示这是一个可选方案。
“More parents have heard about doing it ‘early’,” said Elias Kass, a naturopathic physician and vaccine advocate in Seattle, Washington.
“更多家长已经听说过‘提前’接种的做法，”华盛顿州西雅图的自然疗法医生兼疫苗倡导者埃利亚斯·卡斯说。CDC通常建议在满一岁后接种第一剂MMR疫苗，在四至六岁之间接种第二剂。但卡斯在几年前麻疹病例开始增加时，就开始建议在15个月大时接种MMRV疫苗，该疫苗将第二剂MMR和水痘（varicella）合并为一针。
The CDC typically recommends giving the first MMR shot after age one and the second between the ages of four and six. But Kass began recommending the MMRV shot, which combines the second MMR and chickenpox (varicella) into one, at 15 months of age when measles cases began increasing a few years ago. More parents are taking that recommendation now, he said, adding that their thinking is pretty straightforward: “There’s no reason to wait, measles is here now.”
他说，现在有更多家长采纳这一建议，并补充说他们的想法很直接：“没有理由等待，麻疹现在就在眼前。”芝加哥的母亲玛戈特·泰勒有三个年幼的孩子，他们对MMR疫苗的接种史各不相同。
Margot Taylor, a mother in Chicago, has three young children with three different vaccination histories for the MMR vaccine. “All three of them are fully vaccinated, but it’s had to be accelerated because of all of these increasing cases,” Taylor said.
泰勒说：“他们三个都接种了疫苗，但由于病例不断增加，不得不加快接种进度。我们已经倒退了太多。”她最大的孩子出生于2019年，在一岁和四岁时分别接种了疫苗。泰勒说，麻疹“根本不在我的考虑范围内”。“我甚至想都没想过。”但她的第二个孩子出生于2023年，当儿科医生建议孩子在两岁时接种第二针时，泰勒感到很意外。
“We’ve gone backwards so much.”Her oldest, born in 2019, received her shots at ages one and four. Measles “wasn’t on my radar”, Taylor said. “I wasn’t even thinking about it.”But with her second child, born in 2023, Taylor was surprised when the pediatrician recommended the second shot at age two.
当时芝加哥正在应对麻疹疫情，所以他们还是照做了。她的第三个孩子出生于2025年，在一岁生日后接种了第一针，仅仅三个月后，也就是六月，就接种了第二针。泰勒担心，如果接种时间这么早，疫苗可能效果不佳。但有证据表明，疫苗在更早的年龄接种仍然效果良好；建议在四到六岁之间接种MMR疫苗，更多是出于流程上的考虑，以确保孩子在进入幼儿园前完成两针接种，并减少就医次数，因为其他疫苗通常也在这个年龄段接种。
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 then the second shot only three months later, in June. Taylor worried the shots might not work as well if they were so early. But evidence shows the vaccines still work well at earlier ages; the recommendation to give the MMR dose between four and six years is based more on logistical concerns to ensure children have both shots before they enter kindergarten and to cut down on doctors’ visits because other shots are also typically given at those ages.
泰勒深知MMR疫苗有多么重要。当她的小女儿还太小、无法接种第一针时，她在西得克萨斯州疫情暴发期间于机场接触了麻疹病毒。这个仅一个月大的婴儿随后发烧，他们急忙赶到医院，在负压病房里待到麻疹检测结果呈阴性。“我松了一口气，而且我仍然无法用言语表达我有多么感激”这些疫苗，泰勒说。但她仍然对是否必须做出这些决定感到疑惑。
And Taylor knows how vital the MMR vaccines are. When her third daughter was too young to get 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 afterward, they rushed to the hospital and stayed in a negative-pressure room until the test was negative for measles. “I am relieved, and I still cannot say enough how grateful I am” for the vaccines, Taylor said. But she still wonders at the need to make these decisions at all.
“我从没想过自己还得去研究疫苗接种时间表，”她说。德国在2001年之前与美国有类似的建议，直到一次疫情暴发带来了一波疾病和死亡，促使该国建议在11至14个月时接种第一针，在18至23个月时接种第二针。2020年，他们将第二针调整为第一针后四周接种。
“I never thought that I would have to be learning the vaccine schedules,” she said. 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 shot at 18 to 23 months. In 2020, they moved the second dose to four weeks after the first.
德国科学家卡瑟琳娜·贝克尔表示：“到目前为止，绝对没有任何迹象表明，任何以任何节奏接种过两剂疫苗的孩子，比按照旧规则接种疫苗的人有更高的麻疹风险。”
“There’s absolutely no indication so far that any kid that has been vaccinated twice in any rhythm would have a higher risk of measles than someone who’s been vaccinated according to the old rule,” said Catherina Becker, a scientist in Germany.
她的儿子在接种第二剂麻疹疫苗时只有两岁半——之所以延迟接种，只是因为他当时正在从水痘中康复。贝克尔说，美国疾病控制与预防中心“绝对”应该考虑提出更强烈的建议，让孩子更早接种第二剂。
Her son was two and a half years old when he got his second measles vaccine – and that was delayed only because he was recovering from a case of chickenpox. The CDC should “absolutely” consider a stronger recommendation to give the second shot earlier, Becker said.
一些家长也选择在婴儿六个月大时就接种第一剂——美国疾病控制与预防中心建议在疫情暴发地区、国际旅行前以及接触麻疹后为婴儿接种。这些婴儿还应接种第三剂。
Some parents are also choosing to get their babies the first shot at the age of six months – which the CDC in areas with outbreaks, before international travel, and after exposure to measles. Those infants should also receive a third dose.
如果母亲在怀孕前接种过麻疹疫苗，这种免疫力会在子宫内传递给胎儿，因此婴儿在出生后的头几个月内受到保护。这就是为什么如果婴儿提前接种第一剂，就建议接种第三剂——因为婴儿体内可能仍有一些母体抗体，因此在六个月大时无法对疫苗建立强烈的免疫反应。
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’s why a third dose is recommended if infants receive the first dose early – because it’s possible the baby still has some maternal antibodies and thus doesn’t establish a strong response to a vaccine at six months.
第二剂MMR疫苗与其他加强针不同。大多数人对第一剂就能产生强烈的免疫反应，这就是为什么直到1989年只建议接种一剂。但科学家发现，有些人对第一剂没有反应，需要第二剂——这就是建议接种加强针的原因。这也是为什么1989年之前出生的人现在可能需要接种第二剂。“这是第一次做出反应的第二次机会，”卡斯说。
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. But scientists discovered that some people don’t respond to the first shot and need a second – which is why the booster was recommended. That’s also why people born before 1989 may need to get a second shot now. “It’s a second chance to respond for the first time,” Kass said.
贝克尔通过回顾过去的疫情来了解疫苗的有效性。在1998年阿拉斯加的一次疫情中，一所学校几乎所有学生——总共约2186人——都接种过麻疹疫苗，只有17人患病。她将其与2010年德国一所华德福学校的疫情进行了比较，当时300名学生中近一半未接种疫苗，71人患病。
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 at a Waldorf school in Germany where nearly half of the 300 students were unvaccinated and 71 people were sickened.
她说：“这显示了麻疹疫苗的作用——它能保护你免于感染这种疾病。”
“It shows you what the measles vaccine does for you – it protects you from getting this thing,” she said.