The claim that Independent Presidential candidate Robert F. Kennedy Jr. holds anti-vaccine beliefs is TRUE. Here is an evaluation using the SIFT method of fact checking.
1. Stop and find the source of the claim from the article
The article linked by the original poster is from NPR. The author of the article, Shannon Bond, makes multiple claims that RFK Jr. is anti-vaccine. For instance, they state that "in 2021, he [RFK Jr.] was named one of the top spreaders of misinformation about COVID-19 vaccines on social media" and that "he compared vaccine mandates to Nazi Germany and promoted a film targeting disproven claims about vaccines to Black Americans." Thus, it is clear that the claim in the original post accurately reflects those made in the article.
2. Investigate this Source
NPR is a highly regarded and reputable source that is largely unbiased on the media spectrum (https://adfontesmedia.com/npr-bias-and-reliability/). The author of the article, Shannon Bond, specializes in "covering how misleading narratives and false claims circulate online and offline, and their impact on society and democracy" and has over a decade of journalism experience. Therefore, we can consider this source to be reliable and unlikely to publish misleading/false information.
3. Find Trusted Sources on the same claim/topic
Other trustworthy news outlets have published articles about RFK Jr.'s anti-vaccine opinions. An article by the BBC from March 2024 about the independent candidate states that "the vaccine sceptic has a history of straying from the truth and spreading health information scientists say is false." Another article from the same month by Reuters states that "Kennedy has been criticized for making false medical claims, including that vaccines are linked to autism. He opposed state and federal COVID-19 restrictions and was accused of spreading misinformation about the virus." With these corroborating statements from other trusted sources, we can be confident that the claim made in the original NPR article is likely true.
https://www.bbc.com/news/world-68447223
https://www.reuters.com/world/us/rfk-jr-abortion-vaccines-housing-foreign-policy-2024-03-20/
4. Trace the original first instance of this claim/idea
The first instance of the claim is difficult to find as RFK Jr. has been an opponent of vaccines for years. Here is an AP article from 2021 about Kennedy's anti-vaccine organization and its activities during the COVID-19 pandemic: https://apnews.com/article/how-rfk-jr-built-anti-vaccine-juggernaut-amid-covid-4997be1bcf591fe8b7f1f90d16c9321e. Clearly, there is a long history of this claim being made and it is not a new idea by any means.