[5][6] With Martin Kulldorff and Sunetra Gupta, he was a co-author in 2020 of the Great Barrington Declaration, which advocated lifting COVID-19 restrictions on lower-risk groups to develop herd immunity through widespread infection, while promoting the fringe notion that vulnerable people could be simultaneously protected from the virus.

[14][15] Bhattacharya began his career at the RAND Corporation as an economist (1998–2001), while simultaneously serving as a visiting assistant professor in the Department of Economics at the UCLA.

[23][24] He is a co-author of the Great Barrington Declaration, a proposal arguing for an alternative public health approach to dealing with COVID-19 through "focused protection" of the people most at risk.

In it, Bhattacharya and the two other researchers called on governments to overturn their coronavirus strategies and to allow young and healthy people to return to normal life while protecting the most vulnerable.

[25] The authors conceded that it was hard to protect older people in the community, but suggested individuals could shield themselves and that efforts to keep infections low "merely dragged matters out".

[26][27] In October 2020, the World Health Organization's Director General stated that pursuing herd immunity before vaccination would be "scientifically and ethically problematic" and "allowing a dangerous virus that we don’t fully understand to run free is simply unethical.

"[28][29] Writing at Science-Based Medicine, David Gorski, Professor of Surgery at Wayne State University, argued that Gupta, Bhattacharya, and Kulldorff had either been "politically very naïve" in working on the declaration with the American Institute for Economic Research, or that the doctors were "motivated as much by ideology as their interpretation of COVID-19 public health science".

[34] At the beginning of 2021, Bhattacharya wrote an op-ed in favor of reserving initially limited vaccine supplies in India for patients who had not been previously infected with COVID-19.

[37] The judge determined that the public health restrictions did not violate charter rights, noting that most scientific and medical experts did not support Bhattacharya's views.

[43] In December, with Kulldorff and Scott Atlas, Bhattacharya helped found a program called Academy for Science and Freedom at Hillsdale College, a conservative Christian liberal arts school.

[46] He was also named a senior scholar at the Brownstone Institute, a new think tank launched by Jeffrey Tucker that published articles opposing various measures against COVID-19; Kulldorff and Gupta, his co-authors on the Great Barrington Declaration, have also had roles there.

[54] Justice Barrett delivered the opinion of the majority, stating "plaintiffs failed to show a concrete link between the restrictions that they alleged and conduct of government officials".