• Pfizer's coronavirus vaccine showed no safety concerns that could threaten an emergency authorisation, regulators at the US Food and Drug Administration wrote in documents released Tuesday. 
  • The detailed data shows Pfizer's shot as a highly effective and safe vaccine based on a clinical trial of more than 40,000 participants. 
  • There were temporary side effects that are generally expected with most vaccines. The most common side effects were pain at injection site (84%), fatigue (63%), and headache (55%).
  • An expert panel convened by the FDA is set to meet Thursday to discuss Pfizer's application for an emergency OK. An agency decision could come shortly thereafter in a matter of days. 
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US vaccine regulators released Tuesday the most detailed look yet at a leading coronavirus vaccine candidate, outlining the safety and side effects seen in a massive clinical trial. 

Overall, the findings are positive, with the study suggesting no major safety concerns for Pfizer's vaccine. Most immunized volunteers had temporary side effects shortly after being vaccinated. Those side effects included fatigue, headache, and pain at injection site.

The US Food and Drug Administration is in the process of reviewing the Covid-19 shot for emergency use authorization, with a decision expected in a matter of days. An expert panel is set to meet Thursday to review Pfizer's application and recommend a decision to FDA regulators. 

Pfizer and its German biotech partner BioNTech tested their vaccine in a global study that randomized more than 40,000 volunteers to either get two doses of its vaccine or two doses of a placebo injection.

While Pfizer said it had enough data to show its vaccine was a success at preventing Covid-19 - being about 95% effective - the company had to wait until November 20 to submit its application to accrue enough safety information. The FDA asked for at least two months of follow-up data on more than half the volunteers who have received their second dose.

The most common side effects included fatigue and headache

The results showed that younger people - those under 55 years old - recorded more side effects. These side effects were expected with a vaccine, typically appearing within a couple days of receiving a dose and lasting for only a day or two on average.

In its own summary of the data, FDA scientists said there were "no specific safety concerns identified that would preclude issuance of an EUA". 

Here were the most common side effects after getting Pfizer's vaccine: 

  • Pain at the injection site (84%) 
  • Fatigue (63%) 
  • Headache (55%)
  • Muscle pain (38%)
  • Chills (32%)
  • Joint pain (24%)
  • Fever (14%)

Scientists at the FDA and at Pfizer and BioNTech have been poring over the data, particularly to see if there were any unexpected safety concerns. Encouragingly, they didn't find anything that caused concern, according to the briefing documents released Tuesday. 

FDA regulators noted a "numerical imbalance" in cases of Bell's palsy, a condition that temporarily weakens face muscles. There were four cases of Bell's palsy among the 20,000-plus people who got Pfizer's vaccine, compared to no cases in the placebo group. 

But the FDA notes this frequency of Bell's palsy cases among those getting Pfizer's shot was not any higher than what would be expected for the general population. 

Agency scientists also said that the vaccine's safety profile was "generally similar" across different ages, genders, ethnicities, racial groups, the presence of health conditions, and people with or without evidence of previous coronavirus infections at enrollment.  The only expect ion was that younger people tended to have more frequent side effects.

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