These included fatigue, headache, chills and muscle pain, Reuters reported, while some volunteers also developed fevers, including a few high fevers.
Some were given the vaccine and some a placebo, though the blinded nature of the study means Pfizer cannot identify who has received what.
Kathrin Jansen, Pfizer’s head of vaccine research and development, highlighted the independent data monitoring committee reviewing the study did not express safety concerns, despite having access to the blidned data.
Late-stage studies are underway on over 29,000 people out of the 44,000 required for the trial. Over 12,000 received the second dose.
The pair could have 100mln dose ready by the end of the year, with the ability to supply 1.3bn doses by the end of next year.