The Hang Seng Index fell 2.03 percent, or 579.24 points, to 27,918.14 -- putting it in a correction after falling more than 10 percent from its recent high seen in February.
US Treasury yields were lower as investors sought out the safe haven -- yields go in the opposite direction to prices -- providing respite from a recent increase that had led to worries about a hike in interest rates from the record lows that have been a key pillar of support to a year-long equity rally.
The decision came two days before Spain was to resume use of the AstraZeneca vaccine after the EU's drug regulator deemed the jab "safe and effective".
The EU has so far approved three vaccines -- Pfizer-BioNTech, Moderna and AstraZeneca-Oxford. Three other vaccines are under "rolling review" by the Amsterdam-based EMA -- Novavax, CureVac and Russia's Sputnik.
New Zealand started its national rollout of the Pfizer-BioNTech's COVID-19 vaccine last month and expects to inoculate its entire population by the end of the year.
A week ago, Hungary became the first European Union member to start inoculating people with China's Sinopharm vaccine after rolling out Russia's Sputnik V vaccine as well, even though neither has been granted approval for emergency use by the bloc.
A new change is that it (AstraZeneca jab) can be given to everyone above the age of 18 without any age limit. There has been sufficient data that proves its efficacy also for older people.
Moderna also said Chief Medical Officer Tal Zaks would leave the company in late September.
Moderna on Wednesday said it was expecting to produce 700 million doses in 2021, while attempting to scale up production to as much as 1 billion doses.
However, the unresolved question of who would pay for claims for damages in the event of adverse effects from the inoculations has delayed the delivery.
Though concern has grown over variants of the virus, especially those that appear to spread more easily and render current shots less potent, Fauci sounded a hopeful note on whether another surge was coming.
The Sheba Medical Center’s findings compare with overall efficacy of around 95% in a two dose regimen 21 days apart for the shot developed with Germany’s BioNTech.