The Pentagon said this month it would seek President Joe Biden's approval by mid-September to require 1.3 million military members to get vaccinated against COVID-19
New early data showed that a third dose generated virus-neutralizing antibodies more than 5 times higher in younger people and more than 11 times higher in older people than from two doses
Singapore has vaccinated almost half its 5.7 million population with at least one dose of the vaccines from Pfizer-BioNTech and Moderna. Both have shown efficacy rates of well over 90% against symptomatic disease in clinical trials, compared with Sinovac's 51%.
Vietnam is trying to accelerate its vaccine procurement drive to tackle a more stubborn wave of infections, even though its overall case load and fatality numbers remain relatively low.
Vietnam, with a population of around 98 million, has recorded a total of 10,241 coronavirus cases, with 58 deaths, since the pandemic began. Its domestic inoculation started in March.
The health regulator, Anvisa, said the approval was based on studies by Pfizer that "indicated the vaccine's safety and effectiveness for this age group."
Says a limited quantity of Pfizer vaccine doses have been acquired by Pakistan this month
Minister says a decision should be taken at the international level related to the countries not accepting vaccination certificates of Chinese vaccines as it would create problems for the entire world
A health official said the trial will include around 500 military personnel who were vaccinated with a first dose of AstraZeneca's COVID-19 shot.
The study will examine T cells - immune cells that can destroy virus-infected cells - and neutralising antibodies in those who were given a combination of doses, the health official told reporters.
The approval is highly anticipated after the drugmaker said in March the vaccine was found to be safe, effective and produced a robust antibody responses in 12- to 15-year-olds in a clinical trial.
The vaccine has already been cleared in the United States for those aged 16 and above.
The government had talked with Pfizer last year about the purchase of COVID-19 vaccines but the two sides did not reach a deal on supply of the vaccine it developed with German partner BioNTech SE.
Argentina is distributing Russia's Sputnik V vaccine as well as doses from China's Sinopharm, the Serum Institute of India, and the UN-led COVAX program.