He produced the film Vaxxed: From Cover-Up to Catastrophe, based on the discredited[4] opinions of Andrew Wakefield, and alleges an unsubstantiated connection between vaccines and autism.

[20] Bigtree produced the film Vaxxed: From Cover-Up to Catastrophe, based on the discredited[1][2][3] views of Andrew Wakefield on an alleged connection between vaccines and autism.

The epidemiologist Ian Lipkin wrote that "as a documentary it misrepresents what science knows about autism, undermines public confidence in the safety and efficacy of vaccines, and attacks the integrity of legitimate scientists and public-health officials.

He has since spoken at multiple anti-vaccine events in which he repeats false information about the risks of vaccines and alleges governments are engaged in a vast conspiracy to hide the truth.

[10][24][33][34][35][8] In New York State in 2019, Bigtree was a keynote speaker at several anti-vaccination events targeting the ultra-Orthodox Jewish community in Brooklyn and in Rockland County during a measles epidemic fueled by low vaccination rates.

[10][26] Bigtree gave an anti-vaccine speech as headline speaker at a natural health product conference in Toronto in 2018, but a repeat performance was canceled in 2019 after The Globe and Mail started asking questions.

The weekly webcast quickly became a rallying point for anti-vaccination activists and conspiracy theorists early in the pandemic, according to Professor Dorit Reiss, who studies online COVID-19 disinformation.

[37] Going against the advice of health authorities, he recommended to his viewers to refuse the vaccine when it is developed and to make efforts to actually infect themselves with the virus,[14][17][36] favoring not so much herd immunity as natural selection, with weaker humans dying like the "sick get eaten by the wolves.

[43][44][45][46] By 2023, Bigtree was calling for the imprisonment of public health officials and executives of pharmaceutical companies for favoring vaccination against COVID-19 over the use of ineffective drugs such as hydroxychloroquine and ivermectin, alleging people have been murdered in order to further the agenda of sinister globalist interests.

[42] In August 2020, Bigtree announced that his videos were now distributed on Roku media players, despite the company's prohibition against content that is found to include "false, irrelevant or misleading information".

Among other activities, he participated to an online event bringing together several prominent anti-vaccination activists, such as Mikki Willis, Sayer Ji, Charles Eisenstein, Sherri Tenpenny and Joe Mercola.