Pfizer Inc said Tuesday that participants were mostly showing mild to moderate side effects when given the company’s experimental coronavirus vaccine or a placebo in an ongoing late-stage study.
The company said in a presentation to investors that side effects include fatigue, headache, chills and muscle pain. Some participants in the trial also developed fevers, including some high fevers. The data is blinded, which means that Pfizer does not know which patients received the vaccine or a placebo.
Kathrin Jansen, Pfizer’s head of vaccine research and development, emphasized that the independent data monitoring committee “has access to unblinded data to let us know if they have any safety issues and they haven’t done so to date.”
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The company has enrolled more than 29,000 people in its trial of 44,000 volunteers to test the experimental Covid-19 vaccine it is developing with German partner BioNTech.
More than 12,000 study participants had received a second dose of the vaccine, Pfizer executives said in a conference call with investors.
The comments follow rival AstraZeneca’s Covid-19 vaccine trials that were suspended worldwide on September 6 after a serious side effect was reported in a volunteer in Britain.
AstraZeneca trials resumed in Britain and Brazil on Monday after the green light from British regulators, but remain on hold in the United States.
Pfizer hopes it will likely have results on whether the vaccine works in October.
“We believe, given the very robust immunological profile and also the preclinical profile … that the efficacy of the vaccine is likely to be 60 percent or more,” said Pfizer Chief Scientific Officer Mikael Dolsten.
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