NEW DELHI—The Quad nations—United States, India, Australia, and Japan—are pushing back against the Chinese regime’s vaccine diplomacy. At the first leadership summit of the Quadrilateral Security Dialogue on March 12, the nations announced a partnership to end the pandemic, expand vaccine manufacturing with facilities in India, and provide assistance to the countries in the larger Indo-Pacific region with vaccination and with existing multilateral mechanisms. “Together, Quad leaders are taking shared action necessary to expand safe and effective COVID-19 vaccine manufacturing in 2021 and will work together to strengthen and assist countries in the Indo-Pacific with vaccination, in close coordination with the existing relevant multilateral mechanisms, including WHO and COVAX,” the White House said in a fact sheet released after the summit. Experts said the larger agenda of the informal strategic forum—to forge a union of democracies against authoritarian governments—is making itself visible in the partnership for vaccines as well; India has emerged as a …