Vaccine diplomacy, a form of medical diplomacy, is the use of vaccines to improve a country's diplomatic relationship and influence of other countries. Meanwhile, vaccine diplomacy also "means a set of diplomatic measures taken to ensure access to the best practices in the development of potential vaccines, to enhance bilateral and/or multilateral cooperation between countries in conducting joint R&D, and, in the case of the announcement of production, to ensure the signing of a contract for the purchase of the vaccine at the shortest term." Although primarily discussed in the context of the supply of COVID-19 vaccines, it also played a part in the distribution of the smallpox vaccine.

Commentators have identified vaccine diplomacy occurring as far back as the first vaccine, Edward Jenner's smallpox vaccine. It has also been identified in Soviet involvement with the Albert Sabin polio vaccine. The UN has also brokered ceasefires in order to conduct vaccination campaigns such as with the Taliban in Afghanistan.

Australia promised to ensure early access to a vaccine "for countries in our Pacific family, as well as regional partners in Southeast Asia". to help them fight the COVID-19 pandemic.

China's infection rates and early success in handling the COVID-19 pandemic were sufficiently low that it could send vaccines abroad without domestic objections. By August 2021, China had donated 700 million vaccine doses abroad, greater than the number from all other countries combined. As academic Suisheng Zhao writes, "Just by showing up and helping plug the colossal gaps in the global supply, China gained ground." Moreover, the Center for Strategic and International Studies found that its vaccine diplomatic activities earned China goodwill and influence in several middle-income countries, many of which are also notably involved in the Belt and Road Initiative, indicating that such diplomacy could have improved China's image and strengthened its relationships with countries that wished for, or already took part in, strong relationships with China. However, because most of Chinese distributed vaccines have gone to such middle-income countries, many of the poorest countries are left highly vulnerable, undercutting China's attempts to present itself as a benevolent giver of needed goods and undermining Xi's claim that a Chinese developed vaccine would be treated as a "global public good."

The Sinopharm BIBP vaccine is used for vaccinations by some countries in Asia, Africa, South America, and Europe. Sinopharm produced one billion doses of the BBIB vaccine in 2021, and supplied 200 million doses by May.

CoronaVac is used for vaccinations by some countries in Asia, South America, North America, and Europe. Sinovac had a production capacity of 2 billion doses a year and had delivered 600 million total doses.

Convidecia is used for vaccination by some countries in Asia, Europe, and Latin America. Production capacity for Ad5-NCov should reach 500 million doses in 2021.

China pledged US$2 billion to support efforts by WHO for programs against COVID-19, a US$1 billion loan to make its vaccine accessible for countries in Latin America and the Caribbean, and provide five Southeast Asian countries priority access to the vaccine. The Sinopharm BIBP vaccine and CoronaVac were approved by the WHO as part of COVAX. By July 2021, GAVI had signed advanced purchase agreements for 170 million doses of the Sinopharm BIBP vaccine, 350 million doses of CoronaVac, and 414 million doses of SCB-2019, another COVID-19 vaccine in Phase III trials.