Kathleen Wiederman is not staunchly against vaccines. She simply believes it is better for her child to naturally battle an illness than to be vaccinated against it.
"Doctors don't know everything," said the 42-year-old recruiter, who prefers alternative medicine and gave birth at her home in the well-heeled Virginia suburbs without the aid of a pain-killing epidural.
At first, she and her husband agreed on the matter, but when their marriage ended, he pushed for their daughter to get some of her recommended vaccines and Wiederman relented.
Now her daughter is five and has had a handful of shots, including against chicken pox and measles, but not polio.
And if her child gets sick?
"Then we treat it however you need to treat it and work through it," she told AFP.
Wiederman, who has a law degree, is among a growing number of Americans who oppose vaccines, raising concerns about a resurgence in contagious diseases like measles and whooping cough.
Vaccine hesitancy is increasingly common, and not only when it comes to infant and childhood immunizations, experts say.
Two in three working age adults refuse to get the annual flu vaccine and the same proportion of parents decline the human papillomavirus (HPV) vaccine for young adolescents, according to the US Centers for Disease Control and Prevention.
"The people we are concerned about are the people who are hesitant. The general demographic is well-educated and upper middle class," said Barry Bloom, a professor of medicine at Harvard University.
"I think they are on the rise everywhere."
In recent years, reports linking vaccines to autism have been debunked, but fears of adverse events -- which experts say are rare -- have proven difficult to erase.
Some parents are troubled by the increasing number of vaccines children are given, which have risen from seven in 1985 to 14 today, a result of medical advances, according to the Centers for Disease Control and Prevention.
"I was stunned by the number of vaccines," said Alina Scott, a 37-year-old project manager and mother of a two-year-old son.
Scott said she began reading everything she could find on the topic, even before her child was born, and decided that vaccines were not for them.
"This lasted until about a year ago, when I just felt like I wasn't finding any new information. It's like I hit the end of Internet," she said. "I don't think we will be vaccinating any time soon."
- Religious exemptions -
Nearly all US states require a standard list of immunizations before children can enter school, but they allow religious exemptions for vaccines. Some allow parents to opt out for personal reasons.
Some measles outbreaks in recent years, including in the Orthodox Jewish community in New York City, have been linked to parents refusing vaccines.
"Today you are allowed to have philosophical reasons not to vaccinate and I think that is crazy," said Anne Gershon, director of the Division of Pediatric Infectious Disease at Columbia University Medical Center.
"The reason is that it hurts many people. It is not just your child."
Some young people cannot get vaccines, including those with cancer or immune diseases, and very young infants are vulnerable to pertussis, or whooping cough, until the age of two months when they can get begin to get doses of the vaccine.
Particularly with measles, one of the most contagious diseases, outbreaks will occur unless 94 percent or more of the population is vaccinated, according to Bloom.
Nationwide, vaccination rates among US kindergarteners have stayed high -- near 95 percent.
But a 2011 poll in the journal Pediatrics found that one in 10 parents did not stick to the recommended schedule of vaccines for their child, and a quarter of parents had doubts about vaccine safety.
The United States typically sees about 60 cases of measles per year.
"We don't have a crisis, but nonetheless the trend is going up and the number of immunizations is going down," said Bloom.
- Flu shots, cancer vaccines -
Another trend is resistance to vaccines like the annual flu shot, experts say.
The CDC said in February that two-thirds of adults aged 18 to 65 had not had their seasonal shot, and that hospitalizations in this age group had doubled over last year. Deaths from flu complications were also far higher than usual.
Doctors are also surprised at how many decline the three-dose shot to prevent HPV, a sexually transmitted infection which can lead to cervical cancer in women and cancers of the head, neck, penis and anus in men.
The vaccine is recommended for school age boys and girls before they become sexually active, and can be given as early as age nine.
Just one in three women aged 19 to 26 had been vaccinated in 2012, and just 2.3 percent of men, the CDC has reported.
"I think for physicians, the idea that vaccines could prevent cancers seems phenomenal," said Anne Schuchat, Assistant Surgeon General and director of the National Center for Immunization and Respiratory Diseases.
"It has been a surprise it has not been going like hotcakes."
When it comes to how to communicate the benefits of vaccines to a skeptical public, experts are stumped.
In Bloom's view, vaccines have fallen victim to their own success.
"If they have never seen a kid blinded from measles, or mentally retarded from pertussis, it is very hard in this wonderful, happy, affluent world of kindergartens and first and second grades to see that there is a problem that vaccines are preventing."
凯思琳·维德曼并非是疫苗的坚定反对者，她只是相信，她的孩子通过自身免疫对抗疾病，比接种疫苗要好得多。
“医生并不了解所有的事，”42岁的招聘人员维德曼表示。她喜欢替代疗法，并在位于富饶的弗吉尼亚郊区的家中生孩子，全程不使用硬脊膜外注射麻醉来避免疼痛。
起初，她和丈夫同意这样的做法，但当他们离婚后，她丈夫让女儿接种了一些她所推荐的疫苗，这时，维德曼的态度有所软化。
现在，她的女儿5岁了，已经注射了几种疫苗，包括水痘和麻疹疫苗，但没有接种小儿麻痹症的疫苗。
那么，如果她的孩子病了，该怎么办呢？
“无论需要怎样的治疗，我们都会提供，来治好孩子的病，”她告诉法新社。
反对疫苗接种的美国人数量不断增加，拥有法律学位的维德曼是其中一员，而她却担心像麻疹和百日咳这样的传染性疾病会再次出现。
专家表示，对疫苗持观望态度的现象日益普遍，并不只局限于婴儿和儿童的免疫。
美国疾病控制和预防中心表示，在处于工作年龄的成年人当中，每三个人中就有两人拒绝接受每年的流感疫苗注射，同样比例的父母拒绝让年龄还小的青少年注射人类乳头状瘤病毒(HPV)疫苗。
“我们所担心的是那些持观望态度的人们，他们一般接受过良好教育，属于中上层阶级，”哈佛大学医学教授巴里·布鲁姆说。
“我认为，他们的人数在每个地方都有增加。”
近年来，一些将疫苗同自闭症相联系的报告已被证明是错误的，专家也表示注射疫苗后很少出现不良事件，但是，人们对此所产生的恐惧却很难消除。
疾病控制和预防中心表示，由于医学的进步，一些父母正受困于孩子可接种疫苗数量的不断增长，疫苗数量从1985年的7种增加到现在的14种。
“我对疫苗的数量感到吃惊，”37岁的项目经理艾莉娜·斯科特说，她有一个2岁的儿子。
斯科特表示，她开始阅读她能找到的关于这一主题的所有材料，甚至在她的孩子出生之前就开始了，并且她认为疫苗不适合他们。
“这一行为持续到了一年前，那时，我觉得我无法找到任何新的信息，就像是我已经到达了互联网的尽头，”她说，“我想，我们不会很快就接种疫苗。”
宗教豁免
几乎美国所有的州都要求，孩子进入学校前，要进行一系列规定的免疫接种，但是，他们允许对于疫苗的宗教豁免，一些州允许父母可以因个人原因，不让孩子接种疫苗。
近些年，一些水痘病例爆发，包括在纽约市传统犹太社区的出现，与父母拒绝为孩子接疫种苗密切相关。
“今天，你可以有合理的原因不接种疫苗，但我认为这是疯狂的举动，”哥伦比亚大学医学中心儿童传染性疾病部门的负责人安妮·格申说。
“原因在于，这会伤及很多人，不仅仅是你的孩子。”
一些年轻人不能接种疫苗，包括那些身患癌症或免疫疾病的人。很小的婴儿容易患百日咳，他们在两个月大的时候才能开始接种一些剂量的疫苗。
布鲁姆表示，特别需要注意的是水痘，它是最具传染性的疾病之一，除非94%或更多的人接种了疫苗才能避免大规模的爆发。
就全国而言，在美国的幼儿园儿童当中，疫苗接种率很高，接近95%。
然而，2011年儿科杂志的民意调查发现，1/10的父母没有坚持让孩子接种疫苗推荐计划表上的疫苗，而1/4的父母怀疑疫苗的安全性。
美国每年通常有60例水痘病例。
“我们没有这样的危机，但是即便如此，这一趋势正在上涨，而接受免疫的数量正在下降，”布鲁姆说。
专家说，另一个趋势是对类似每年流感疫苗的抗拒。
疾病控制中心（CDC）在二月曾表示，18到65岁的成年人当中，有2/3的人没有接受季节性疫苗注射，这个年龄群体的住院人数在去年增加了一倍，流感并发症引发的死亡人数也远高于平常。
注射预防HPV的三剂预防针数量大量减少，医生也对此感到惊讶。HPV通过性接触感染，会导致女性的宫颈癌，以及男性头部、颈部、生殖器和肛门的癌症。
这一疫苗建议在学龄儿童性征活跃前注射，也可以早在9岁时就接种。
CDC报告称，2012年，19到26岁的女性中，1/3接种了疫苗，而只有2.3%的男性接受了疫苗注射。
“我认为对内科医生而言，疫苗能够预防癌症似乎很惊人，”外科总医师助理及国家免疫和呼吸疾病中心负责人安妮·舒查特说。
“令人吃惊的是，它却没有那样畅销。”
面对挑剔的公众，如何与他们交流疫苗的好处，这难倒了专家。
在布鲁姆看来，疫苗已经成为了他们自身成功的受害者。 “如果他们从未见过一个孩子因水痘而致盲，或因百日咳而智力发展受阻，就很难在美好、快乐和丰富的幼儿时期和一二年级时发现这个问题，即疫苗正受到人们的抗拒。”