A man receives a dose of COVID-19 vaccine during a door-to-door COVID-19 vaccination campaign in Nagaon district of India's northeastern state of Assam, Nov. 29, 2021. Local government in Assam has launched a door-to-door COVID-19 vaccination campaign to increase vaccine coverage. (Str/Xinhua)  

A man receives a dose of COVID-19 vaccine during a door-to-door COVID-19 vaccination campaign in Nagaon district of India's northeastern state of Assam, Nov. 29, 2021. Local government in Assam has launched a door-to-door COVID-19 vaccination campaign to increase vaccine coverage. (Str/Xinhua)

Medical workers walk into a yard during a door-to-door COVID-19 vaccination campaign in Nagaon district of India's northeastern state of Assam, Nov. 29, 2021. Local government in Assam has launched a door-to-door COVID-19 vaccination campaign to increase vaccine coverage. (Str/Xinhua)

A woman receives a dose of COVID-19 vaccine during a door-to-door COVID-19 vaccination campaign in Nagaon district of India's northeastern state of Assam, Nov. 29, 2021. Local government in Assam has launched a door-to-door COVID-19 vaccination campaign to increase vaccine coverage. (Str/Xinhua)

Medical workers walk on a road during a door-to-door COVID-19 vaccination campaign in Nagaon district of India's northeastern state of Assam, Nov. 29, 2021. Local government in Assam has launched a door-to-door COVID-19 vaccination campaign to increase vaccine coverage. (Str/Xinhua)