A health worker applies a dose of the AstraZeneca vaccine during the first day of a three-day COVID-19 vaccination campaign for people over age 35 in the Complexo da Maré favela of Rio de Janeiro, Brazil, Brazil, Thursday, July 29, 2021. Some recipients will be monitored to study the rate of protection the vaccines provide and the extent to which virus variants are circulating. (Photo by Bruna Prado/AP Photo)

A frontline worker reacts as she receives a dose of AstraZeneca's COVISHIELD vaccine, produced by the Serum Institute of India, during the coronavirus disease (COVID-19) vaccination campaign at a medical centre in New Delhi, India, February 24, 2021. (Photo by Anushree Fadnavis/Reuters)

Medical staff administering the dose of Moderna COVID-19 Vaccine at the M A G Osmani Medical College & Hospital vaccination center in Sylhet, Bangladesh on July 26, 2021. (Photo by Md Rafayat Haque Khan/ZUMA Press Wire/Rex Features/Shutterstock)

A health worker pretends to give a shot to a girl's doll to help put her at ease before giving her a shot of the Coronavac vaccine for COVID-19, at a sports center as children age 5 – 11 start getting vaccinated in Asuncion, Paraguay, Monday, January 31, 2022. (Photo by Jorge Saenz/AP Photo)

A health worker gives a polio vaccine to a girl on a street in Lahore, Pakistan, Monday, June 27, 2022. Pakistan launched a new anti-polio drive on Monday, with the goal to vaccinate a million children across Pakistan. (Photo by K.M. Chaudary/AP Photo)

A little girl holding her newborn sister waits for their turn in a queue during a vaccination campaign under the supervision of the Syrian Arab Red Crescent (SARC) humanitarian nonprofit organization, in the besieged Syrian town of Douma, Syria, 23 May 2017. According to a statement from SARC, in the city of Douma some 12,809 children under the age of five were immunized in a vaccination campaign to prevent measles and poliomyelitis. The campaign was the first of its kind with the participation of 100 volunteers. SARC has been delivering vaccines to 17 health centers approved for vaccination campaigns in towns and villages in the Eastern Ghouta area. (Photo by Mohammed Badra/EPA)

In this photograph taken on February 18, 2016, Pakistani children ride on swings in the predominantly Pashtun Korangi District of Karachi. In a rundown district of Karachi, Rabia balks at a neighbour's proposal to vaccinate her children, demonstrating one of the biggest hurdles to eradicating polio in Pakistan by the end of the year: confused and frightened parents. (Photo by Asif Hassan/AFP Photo)

A school girl reacts as a health worker inoculates her with the dose of Pfizer-BioNTech vaccine against the Covid-19 coronavirus for the 12-15 years age group at an educational institution in Colombo on January 7, 2022. (Photo by Ishara S. Kodikara/AFP Photo)