Between 30 to 40 countries are not able to provide second doses of COVID-19 vaccines to their populations, especially those expecting vaccines from AstraZeneca, officials of the World Health Organization (WHO) said on Friday.

"We have a huge number of countries currently that have had to suspend the rollout of their second doses of vaccine," said Bruce Aylward, Senior Advisor to the WHO Director-General on Organizational Change.

Many countries that were expecting AstraZeneca vaccines from the Serum Institute of India, distributed through the WHO-led COVAX program, had seen their supplies being reduced as the manufacturer had to prioritize India's outbreak in April 2021.