"We have been clear that independent, technically sound investigation is what our focus is on, and once this is reviewed, we'll have an assessment about the steps forward,"
EU lawmaker Peter Liese, from the same party as German Chancellor Angela Merkel, said the report left him speechless, and he urged AstraZeneca to clarify the situation.
The recommendation comes after more than a dozen European countries suspended use of the AstraZeneca vaccine amid concerns over the risk of blood clots.
John Nkengasong, director of the Africa Centers for Disease Control and Prevention, told a news conference the "benefits still outweigh the risks" and countries should "move forward".
Antarctica was one of the last places on Earth to be affected by the virus, but on December 21, an outbreak was reported at a Chilean army base, with 36 people infected.
"The WHO Global Advisory Committee on Vaccine Safety is carefully assessing the latest available safety data for the AstraZeneca vaccine. Once that review is completed, WHO will immediately communicate the findings to the public," it said in a statement a day after experts held a closed-door meeting.
COVAX, backed by WHO and the Global Alliance for Vaccines and Immunization, aims to secure 2 billion vaccine doses by the end of 2021.
In early March, it said the target was to deliver 237 million doses of AstraZeneca's shot to 142 countries by the end of May, and it also shipped its first Pfizer shots.
The European Medicines Agency (EMA), which is holding a special meeting on Thursday, echoed the WHO's calls for calm and said it was better to get the vaccine than not.
Experts believe that SARS-CoV-2, the new coronavirus that causes Covid-19, originally came from bats, and jumped into humans via an intermediate animal.
The supply issues added to the firm's troubles, with some countries including Denmark, Norway and Iceland suspending use of its shot over concerns over side effects such as blood clots.
Faced with such "devastating" effects, Fore urged for children to be placed "at the heart of recovery efforts," particularly by "prioritizing schools in reopening plans."